Physics, Biogeochemistry and Ecology of Upwelling ...genus.zmaw.de/fileadmin/user_upload/genus/template/Meteor_100_1... · c/o MARUM – Zentrum für ... (MOM) and filament study

METEOR-Berichte

Physics, Biogeochemistry and Ecology of Upwelling Filaments and Boundary Zones off Namibia - GENUS II

Cruise No. M100/1

September 1 – October 1, 2013 Walvis Bay (Namibia) – Walvis Bay (Namibia)

F. BUCHHOLZ

Editorial Assistance:

DFG-Senatskommission für Ozeanographie MARUM – Zentrum für Marine Umweltwissenschaften der Universität Bremen

2014

The METEOR-Berichte are published at irregular intervals. They are working papers for people who are occupied with the respective expedition and are intended as reports for the funding institutions. The opinions expressed in the METEOR-Berichte are only those of the authors. The METEOR expeditions are funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium für Bildung und Forschung (BMBF). Editor: DFG-Senatskommission für Ozeanographie c/o MARUM – Zentrum für Marine Umweltwissenschaften Universität Bremen Leobener Strasse 28359 Bremen Author: Prof. Dr. Friedrich Buchholz Telefon:+49-471-4831-2444 Alfred Wegener Institut Telefax:+49-471-4831-1149 Helmholtz-Zentrum für Polar-und e-mail:[email protected] Meeresforschung (Building A-1195) Am Handelshafen 12 D-27570 Bremerhaven Citation: F. Buchholz (2014) Physics, Biogeochemistry and Ecology of Upwelling Filaments and Boundary Zones off Namibia - GENUS II - Cruise No. M100/1 – September 1 – October 1, 2013 – Walvis Bay (Namibia) – Walvis Bay (Namibia). METEOR-Berichte, M100/1, 45 pp., DFG-Senatskommission für Ozeanographie, DOI:10.2312/cr_m100_1 _________________________________________________________________________________ ISSN 2195-8475

2 METEOR-Berichte, M100/1, Walvis Bay –Walvis Bay, September 1 – October 1, 2013 _______________________________________________________________________________________

Table of Contents page

1 Summary ............................................................................................................................................................ 3

2 Participants ........................................................................................................................................................ 4

3 Research Programme ......................................................................................................................................... 5

4 Narrative of the cruise........................................................................................................................................ 6

5 Preliminary Results ............................................................................................................................................ 8

5.1 Sub-Project 2: Hydrographic measurements ............................................................................................... 8

5.1.1 Meteorological conditions .................................................................................................................. 8

5.1.2 Hydrographic conditions across the Namibian shelf........................................................................... 9

5.1.3 Dynamics of upwelling filaments ..................................................................................................... 13

5.1.4 Phytoplankton ................................................................................................................................... 16

5.2 Sub-Project 4 Geo: Biogeochemistry: Carbon and Nutrient Cycling ........................................................ 19

5.3 Sub-Project 4 Bio: Ichthyoplankton Studies .............................................................................................. 23

5.4 Sub-Project 5: Micro- and Mesozooplankton, Sampling and ROV Deployments, Benthos Sediments .... 27

5.5 Sub-Project 6: Distribution and Physiology of Calanoid Copepods in an Upwelling Filament and in Relation to the Oxygen Minimum Zone in the Northern Benguela System .............................................. 34

5.6 Sub-Project 7: Krill as Indicators of Environmental Variation and as Pivotal Components of the Plankton of the Northern Benguela Current System ................................................................................................. 36

5.7 NatMIRC Monthly Oceanographic Monitoring (MOM) and filament study ............................................ 38

6 Ship’s Meteorological Station.......................................................................................................................... 39

7 Station List M100/1 ......................................................................................................................................... 39

8 Data and Sample Storage and Availability ...................................................................................................... 42

9 Acknowledgements .......................................................................................................................................... 43

10 References ....................................................................................................................................................... 43

METEOR-Berichte, M100/1, Walvis Bay –Walvis Bay, September 1 – October 1, 2013 3

1 Summary Within the framework of IMBER - Integrated Marine Biogeochemistry and Ecosystem Research – a multidisciplinary group continues studies of the status and development of the Northern compartment of the Benguela Current region off Namibia with funds supplied by the German BMBF-project GENUS II. Networking with African partners is an integral part of the approach, aiming at assessments of changes of productivity of the ecosystem and associated impacts on greenhouse gas emissions in future scenarios of expected effects of Global Change. The current cruise NamBo is tuned to the seasonal maximum of upwelling in late winter in Sept/October 2013 and is planned to be complemented by NamuFil to cover the seasonal minimum in early 2014. The current cruise in 2013 investigated the formation and succession of processes within filaments of upwelled coastal water which transport coastal communities westward into the open ocean. The abiotic and biotic dynamics and fluxes along and across the boundaries of developing filaments, as well as exchanges between water column and sediments were studied within and associated to these conspicuous and characteristic structures of the Benguela upwelling region. Zusammenfassung Als deutscher Beitrag zum IMBER – Rahmenprogramm - Integrated Marine Biogeochemistry and Ecosystem Research – setzt eine multidisziplinäre Forschergruppe ihre Arbeiten fort, bezogen auf den Status und die Entwicklung des nördlichsten Kompartiments des Benguela-Strom-Systems vor Namibia im Rahmen des BMBF-Projekts GENUS II. Die Vernetzung mit afrikanischen Partnern ist ein integraler Ansatz des Vorhabens, mit der Zielsetzung, die Variation und Variabilität des Ökosystems und dessen Auswirkung auf die Emission von Treibhausgasen zu erfassen und auf Szenarien der erwarteten Effekte des Globalen Wandels beziehen zu können. Die Reise NamBo findet im späten Winter, dem saisonalen Maximum des Auftriebs statt und wird Anfang 2014 durch eine zweite Reise NamuFil, zum Auftriebs-Minimum, ergänzt. NamBo 2013 dient dem Studium der Formierung und der Abfolge von Prozessen in Filamenten im Auftriebswasser, das komplette Lebensgemeinschaften von der Küste nach Westen in den offenen Ozean transportiert. Die abiotische und biotische Dynamik sowie die Stoffflüsse zwischen und entlang der Grenzflächen und -schichten, ebenso wie der Austausch zwischen Sediment und Wassersäule, dieser für das Gebiet typischen Strömungs-Strukturen wurde eingehend untersucht.


2 Participants Name Task Institution 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Buchholz, Friedrich Prof Dr Buchholz, Cornelia Dr Werner, Thorsten Dr Mlambo, Lindan BSc Mohrholz, Volker Dr Heene, Toralf Schmidt, Martin Dr Wasmund, Norbert Dr De Klerk, Arnold MSc Bahlmann, Enno Dr Jacob, Juliane MSc Beyn, Fabian MSc Frame, Caitlin Dr Flohr, Anita MSc Peterke, Dieter Lendt, Ralf Libuku, Victor MSc Geist, Simon Dr Edward, Josefine BSc Koppelmann, Rolf Dr Martin, Bettina Dr Bohata, Karolina MSc Bruhn, Jörg Horaeb,Richard MSc Currie, Bronwen Dr Schukat,Anna Dr Giunio, Marina BSc Stelzner, Martin

TP7 Krill Chief Scientist TP7 Krill TP7 Krill TP7 Partner Krill TP2 Oceanography TP2 Oceanography TP2 Oceanography TP2 Phytoplankton TP2 Partner Phytoplankton TP3 Geochemistry TP3 Geochemistry TP3 Geochemistry TP3 Geochemistry TP4 Biogeochemistry TP4 Biogeochemistry TP4 Biogeochemistry TP4 Biogeochemistry TP4 Ichthyoplankton TP2 Partner Ichtyoplankton TP5 Zooplankton TP5 Zooplankton TP5 Zooplankton TP5 Zooplankton TP5 Partner Zooplankton TP5 Partner Benthos TP6 Copepods TP6 Copepods Meteorology Technician

AWI AWI AWI AWI Zimbabwe IOW IOW IOW IOW NatMIRC Namibia IfBM IfBM/HZG IfBM/HZG IfBM/Uni Basel/USA ZMT ZMT IfBM NatMIRC Namibia ZMT NatMIRC Namibia IHF IHF IHF IHF NatMIRC Namibia NatMIRC Observer MarZoo (UHB) MarZoo (UHB) Croatia DWD

Participating Institutions: AWI Alfred-Wegener-Institut für Polar- und Meeresforschung,

Am Handelshafen 12, D-27570 Bremerhaven, Germany HZG Helmholtz Zentrum Geesthacht, Institut für Material und

Küstenforschung, Max-Planck-Straße 1, D-21502 Geesthacht, Germany IfBM (UHH) Institut für Biogeochemie und Meereschemie, Universität Hamburg,

Bundesstraße 55, D-20146 Hamburg, Germany IHF Institut für Hydrobiologie und Fischereiwissenschaft, Universität

Hamburg, Große Elbstraße 133, D-22767 Hamburg, Germany IOW Leibniz-Institut für Ostseeforschung Warnemünde,

Seestraße 15, D-18119 Rostock-Warnemünde, Germany


MarZoo (UHB) Marine Zoologie, FB-02, Universität Bremen, Leobener Straße, D-28359 Bremen, Germany

NatMIRC National Marine Information and Research Centre Strand Street, Swakopmund, Namibia

ZMT (Z) Leibniz-Zentrum für Marine Tropenökologie Bremen, Fahrenheitstraße 6, D-28359 Bremen, Germany

3 Research Programme The Meteor cruise M100/1 was carried out as a joint cruise of the GENUS consortium, representing the BMBF project Geochemistry and Ecology of the Namibian Upwelling System. It is the sixth cruise in a series of expeditions covering the period from 2008 to 2013. The cruise greatly profited from the direct interaction and transfer of knowledge with participating Namibian colleagues. In turn, students were instructed together in the framework of the GENUS capacity building programme. In addition to other objectives, the cruise contributes to the key physical oceanography and modeling research themes in GENUS II, these are:

Filaments and mesoscale dynamics and the impact on the availability of nutrients and on exchanges of CH4 and CO2 and trace cases between atmosphere and ocean

Primary production and phytoplankton succession in relation with the physical forcing conditions

Swell, internal waves and turbulent mixing at the sediment-water-interface Plankton organisms and their feedback on the oxygen and carbon cycle with special

consideration of calcifying primary producers and micro-, meso-, macro-zooplankton and ichthyoplankton

The main focus of the investigations is on the structure and dynamics of upwelling filaments. The field data obtained during the cruise will be used to understand the impact of upwelling filaments on the ecosystem. The following hypotheses will be tested:

1. Surface and deep filaments, and other mesoscale structures control the zonal transport of upwelled water.

2. Vertical mixing at the thermocline and horizontal mixing at fronts and interfaces drive a significant transport of nutrients into the aging upwelling water.

3. Filaments are relatively isolated water bodies, where the temporal changes of nutrient availability determine the plankton succession.

4. Local fronts are hot spots of primary production (e.g. filament edges, upwelling fronts) and as a consequence of zooplankton growth and performance

Furthermore, the Meteor cruise M100/1 provided distributions of physical and geochemical key parameters and of performance of phyto- and zooplankton in late austral winter. Which expand the existing series of hydrographic and ecological data in the northern Benguela.


Fig. 3.1 Map of stations and ship track of Meteor cruise M100/1. Black dots and labels indicate CTD stations.

Yellow shaded tracks were covered with ScanFish measurements

4 Narrative of the cruise RV METEOR departed from the pier at Walvis Bay harbour at 09:00 on 1st September, 2013 heading for the Walvis Bay Transect along the 23°S – parallel. Namibian colleagues deployed a WP2-net for zooplankton in the frame of a long term series observation at fixed stations until 70 nm offshore while routine stations of CTD and various multinets for plankton were run. The Namibian monitoring line was paralleled with vanVeen grab samples.


Continuous measurements of CO2 and methane in the air and surface waters were initiated and continued underway.

The synoptic work was a repeat of previous cruises to be set in relation to seasonal and interannual environmental variability. In the morning of 3rd Sep a long term mooring was deployed and a short term mooring set until Feb 2014 carrying ADCPs and TSF-sensors at 130m depth.

From there, a transect was run with a Scanfish undulating between 120 m and the surface measuring TSF, accompanied partly by a towed Katamaran with an ADCP on board avoiding the ship’s disturbance. The transect ended at 17.3°S, the Kunene Transect and run parallel to the coast to record cross sections of upwelling filaments.

Upon arrival, the data recorded was evaluated and compared with SST and Chl_a images from the MODIS and microwave band satellites received in the meantime.

A conspicuous, well developed filament was identified at 20° S and chosen for intensive study. A coast parallel Scanfish- transect N-S at 30 nm offshore initiated the study, followed by deployments at stations out-South, S-front, centre, N-front and out-North, taking water samples and running net-hauls all along. This included a horizontal haul with a 1m 2 Double-MOCNESS opening and closing 18 single nets across the filament at 30 m depth. Finally, a MSS, micro structure sonde, transect was run North.

Further cross section transects were conducted at 60 and 90 nm offshore and coastal waters were sampled in the end. In this way, a most complete picture of a well-developed filament was obtained, possibly with unprecedented precision of atmospheric, oceanographic, geochemical and ecological measurements between 7th and 15th Sep.

On the 15th, a N-S coast parallel transect was run towards the 23°S parallel with underway systems running due to a medical case to be delivered at Walvis Bay and back up North until the coastal station of Kunene Transect was reached at 17.3° S. On the 18th Sep a bottom ADCP was moored to record until Feb 2014, at 17°60.0S; 11°40.8E.

On the Kunene Transect at 17.3°S the shelf stations until 400 m depth were sampled for our long term synoptic programme of GENUS on the 18th and 19th Sep. An underway measuring transect was run back towards 23°S. A brief call at Walvis Bay was necessary for one person to disembark for medical treatment.

On 21st work was resumed at two coastal stations at 24.5°S at a prospective phosphate mining site with vanVeen grab and WP2 nets of Namibian colleagues. Subsequently, sampling of the Walvis Bay line at 23°S was resumed by recovering the short term mooring at 130 m and completing the transect with the slope stations at 400 and 900 m and an offshore station at 3000 m until 25th Sep.

In the meantime, satellite images were received and the further development of the 20°S – filament followed. Unexpectedly, the initially sampled structure persisted and it was decided to conduct a second cross section campaign through it, which began with a Scanfish transect on 26th Sep from the South. From the Northern endpoint a brief excursion to the West at the shelf break was conducted and zooplankton sampled at 600, 1000, and 1800 m and related to the pronounced OMZ, oxygen minimum zone, including experimentation on hypoxia tolerance. In the morning of 28th September, the second Filament cross section was done, starting North of the filament – North front – Centre – South of filament as a repeat of the initial 30 nm offshore


transect and research concluded on 29th Sep, 22:00 with a celebration in the bar. The cruise ended 1st October, 09:00 at the pier of Walvis Bay harbor.

5 Preliminary Results

5.1 Sub-Project 2: Hydrographic measurements (Volker Mohrholz, Toralf Heene, Martin Schmidt)

5.1.1 Meteorological conditions (V. Mohrholz, M. Schmidt)

During the first five days of the cruise a strong pulse of southerly winds forced upwelling at the west coast of southern Africa (Fig. 5.1.1). The mean wind speed was between 12 and 14 m/s with gusts of 16m/s. On 5th of September the wind speed decreased significantly. The following calm period lasted until September 8. On the next day the usual trade wind restarted with wind velocities between 10 and 12 m/s. The wind kept this direction and strength for two weeks until 25th September. On 21st September a very strong but only short wind pulse reached wind speeds of up to 20 m/s. That was the maximum wind speed observed during the entire cruise. After a calm day on 26th September the southerly trade wind restarts again with wind speeds of up to 15 m/s.

The air pressure followed a semi diurnal cycle, with only minor excursions around a mean value of 1017 hPa. The air temperature varied between 12 and 16°C. Due to the typical high cloud coverage only a weak day and night cycle was observed. Most clouds were classified as low stratus (100-600m high). As a tendency, cloud coverage decreased during the day and the sun became visible after noon. This limited the applicability of satellite images in the visible band. Humidity was relatively high, between 75% and 100% during the entire cruise. The global radiation was strongly related to the cloud coverage. Maximum values, at noon on sunny days, were about 1000 Wm-2.

Fig. 5.1.1 Stick plot of wind vector measured by the ship weather station of FS Meteor. The yellow shaded areas

indicate periods of winds forcing upwelling in the northern Benguela. SF scanfish, MSS microstructure sonde.


5.1.2 Hydrographic conditions across the Namibian shelf (V. Mohrholz, M. Schmidt, T. Heene)

All data were taken under GENUS and made available through the projects’ data repositories. Sea surface temperature distributions in the investigation area were compiled daily from data of TMI and AMSRE satellites (Fig. 5.1.2).

During the first half of the cruise medium to strong upwelling was observed at the entire Namibian coast. During that period the temperature in the Lüderitz cell was decreasing, pointing to enhanced upwelling. Several filament structures were visible off northern Namibia. Day by day the filaments changed their shapes, disappeared and became visible again. That does not mean that the filaments itself undergo rapid changes, but the surface signature in SST is fluctuating by variable heat fluxes and also by uncertainties in the SST calculation from IR and microwave data. Warm waters from the Angola Gyre were observed north of 16°S. No significant southward movement of these water masses was detected.

Due to the relatively constant wind forcing the SST distribution did not show significant changes during the second half of the cruise. The SST picture from 27th September indicated a slightly relaxed upwelling, caused by the calm conditions on 26th September.

The sea surface temperature, measured by the ships thermo-salinograph, varied between 12°C in coastal upwelling cells and 16°C in off shore areas.

Fig. 5.1.2 SST distribution off Namibia derived from TMI-AMSRE composite remote sensing data during the

second part of M100/1. Images date from left to right: 01.09.2013, 11.09.2013, 27.09.2013. Temperature range from 11 (red) 24.5 °C (violet).

The general hydrographic conditions on the Namibian shelf were investigated by CTD profiles and the vessel mounted ADCP along three cross shelf transects at 23°S (Walvis Bay), 20°S (Terrace Bay) and 17.5°S (Kunene) ref. Figs. 5.1.2 to 5.1.6.

The Walvis Bay transect was first worked during strong upwelling conditions from 01st to 02nd September 2013. The transect consists of 9 CTD stations, that are also covered on a bimonthly basis by the NatMIRC institute at Swakopmund. The strong wind forcing supported coastal upwelling during the first days of the cruise. The temperature stratification indicates an


active coastal upwelling pattern within the first 20 nm. from the shore. The temperature in the surface layer ranged from approximately 14.5°C at the open ocean down to 11.5°C near the coast. Generally, the vertical temperature stratification was weak and no pronounced thermocline was found.

Maximum salinity was located at intermediate depths of around 70 to 100 m, outside the belt of active coastal upwelling. The less saline water in the surface layer may have originated from an overlay of recently upwelled water on top of the more saline waters of intermediate depth. The salinity near the coast compared to the salinity values that were found at around 150 to 230 m depth over the outer shelf areas.

Fig 5.1.3 Distribution of temperature and salinity at the Walvis Bay transect (01./02.09. 2013).

The surface mixed layer was well ventilated. In contrast, below 50 to 60 m the entire water column was oxygen depleted. In the bottom layer oxygen concentrations were at a very low level, but above zero at mid shelf and outer shelf area. The inner shelf stations were covered by anoxic bottom water. The oxygen concentrations correlate with the distribution of central water. However, the anoxic conditions at the inner shelf were caused most probably by high local oxygen consumption.

Fig. 5.1.4 Distribution of oxygen concentration and SACW fraction at the Walvis Bay transect (01./02.09. 2013).


Fig. 5.1.5 Distribution of Chl-a fluorescence and turbidity at the Walvis Bay transect (01./02.09. 2013).

The chlorophyll-a fluorescence shows high primary production in the surface layer, except in a narrow band near the coast. The pattern fits very well to the waters with high oxygen concentration. The turbidity signal is enhanced in the surface layer where also the chlorophyll-a fluorescence is high. However maximum turbidity values were measured in the bottom layer of the inner shelf stations. This can be caused by accumulation of detritus from the surface bloom and/or by resuspension of sediment due to the action of incoming swell, which was high during the time of the measurements.

The current measurements along transect show a complex pattern, that was dominated by the northward flow of 10 to 20 cm/s above mid shelf and inner shelf areas. Generally, the measured currents are a superposition of several processes with comparable magnitude. These are mainly wind driven Ekman dynamics, coastal trapped waves, inertial oscillations and tides.

Fig. 5.1.6 Current velocity at the Walvis Bay transect (01./02.09. 2013) measured with the VMADCP 75kHz.

The Walvis Bay transect was worked again on 22.-25.09.2013. Five CTD stations were performed between 14°03’E and 11°48’E, covering also waters with oceanic conditions. The transects of the western most stations consisted exclusively of ESACW in the central water layer. Towards the coast the fraction of SACW was slightly increasing. However, only above the shelf edge the SACW fraction show higher values of about 50%. The core of AAIW was found near 800 m depth. Fig. 5.1.7 compares the TS properties of the first and second run of the Walvis Bay transect.


Fig. 5.1.7 TS-diagram of the inner Walvis Bay transect (left) and of the second coverage with oceanic stations

(right).

The Terrace Bay transect at 20°S covers the shelf area inside the 400 m isobaths. The transect was worked during a period with strong south westerly wind. As expected, the patterns of temperature, salinity and oxygen revealed the typical shape for active upwelling (not shown). Water temperatures of about 12°C near the coast suggested upwelling of water from a depth layer between 150 to 200 m. The thermocline at the off shore stations was found at about 100 m depth. Salinity decreased with increasing depth and towards the coast. An intermediate salinity maximum, which is typical for intense upwelling, was only observed at a single mid shelf station. The water column below the thermocline was covered by sub-oxic to anoxic water, which is lifted to the surface in the vicinity of the coast. The core of oxygen depleted water correlated with the pattern of the maximum SACW fraction.

The Kunene transect (17.5°S) along the Angolan-Namibian border was the northern most transect in the investigation area. It consisted of only 4 CTD stations, since the work on the transect was stopped due to a medical incident. The area is characterized by the extremely narrow shelf and the steep slope at the shelf edge. The transect also marked the long term mean position of the Angola Benguela frontal zone. However, during the cruise M100/1 most of this transect was covered by a 150 m thick layer of cold upwelled water. SST images depict the position of the ABFZ near 16°S, which indicates the usual northward shift of the frontal zone in austral winter. At the coast, the patterns of temperature and salinity indicate coastal upwelling from a depth of about 200 m.

The surface layer was moderately ventilated, but not saturated. Below the surface layer of about 150m thickness the oxygen concentration decreased to less than 0.5 ml l-1 at 400 m depth. However, anoxic water was not detected.

As expected, the central water layer at the Kunene transect consisted mainly of oxygen poor SACW. Only at station 36 a significant fraction of ESACW was detected in the upper 150 m. The AAIW core was located at 800 m depth.

The data from CTD and Scanfish were used to derive horizontal distributions of physical

parameters. These pictures should be interpreted with caution, since the data were collected over a period of 27 days. However, they provide an impression of the general distribution of hydrographic parameters in the northern Benguela.


In the surface layer at 20 m depth the temperature distribution shows a west east gradient with the cooler water at the coast indicating the active coastal upwelling along the entire coast (Fig. 5.1.8). Additionally, a slight north south gradient was observed due to the transition from tropical conditions near the Kunene to the subtropics in the south of the investigation area.

Fig. 5.1.8 Horizontal distribution of temperature, salinity, oxygen and chlorophyll-a fluorescence off Namibia at

20 m depth (based on CTD and ScanFish data 01.09. - 27.09.2013).

The salinity distribution was characterized the typical upwelling induced cross shelf gradient and by a southward decrease in salinity from 35.6 at the Kunene mouth down to 34.9 near Walvis Bay. Surface oxygen concentrations were reduced in a narrow coastal belt along the entire coast, indicating coastal upwelling of water from subthermocline layers. The maximum chlorophyll-a fluorescence in the surface layer was located in some pronounced spots 60 to 80 nautical miles off the coast.

5.1.3 Dynamics of upwelling filaments (V. Mohrholz, M. Schmidt, T. Heene)

The main purpose of the cruise was to obtain data on the mesoscale dynamics of an upwelling filament. From 03 to 06 September an along-shelf transect with ScanFish (undulating CTD) and towed ADCP was performed to detect an upwelling filament for the filament study. The distance to the coast was approximately 60 nm. The transect started at the latitude of Walvis Bay (23°S) and ran at approximately 60 nm distance to the coast up to the Kunene mouth at 17.3°S. The ScanFish measurements covered the upper 100 to 120m of the water column.

Salinity and temperature showed a general increase from south to north overlain with patterns of smaller scale patterns caused by upwelling and filament dynamics (Fig. 5.1.9). Two distinct upwelling filaments were crossed along the transect. The first was located off Terrace Bay 19.8°S and 20.5°S. This compares to the position of the “northern Namibian cell”. The second filament structure was found between 17.8°S and 18.8°S. Both structures have a cold core bordered by warmer water bodies. Also the salinity was slightly decreased inside the filaments.


The vertical extent of both filaments was at least 100 m. The measurements were not deep enough to reach the true bottom of the structures.

Fig. 5.1.9 Distribution of temperature and salinity at the along-shelf transect (03. - 06.09. 2013).

The core of both filaments depicted a slightly decreased oxygen concentration (Fig. 5.1.10). This indicated that the upwelling water inside the filament had not reached the equilibrium with the atmosphere. In the deeper layer narrow pattern of low oxygen concentration were observed, that were also found in the distributions of temperature and SACW fraction. These “peaks” occurred regularly along the transect, possibly due to vertical excursions of internal interfaces caused by a passing coastal trapped wave.

The composition of central water showed the typical increase of the SACW fraction from south to north (Fig. 5.1.10). However, there was no smooth change. At least two distinct fronts were observed. The change from poor ESACW to a mixture with 50% SACW was located at the northern edge of the filament at 20°S. The second frond with a change to water with 80 to 100% SACW was found at the southern edge of the second filament core (18.5°S).

Fig. 5.1.10 Distribution of dissolved oxygen and SACW fraction at the along-shelf transect (03. - 06.09. 2013).

The distributions of chlorophyll-a fluorescence and turbidity depict a number of small- and mesoscale patterns. Chlorophyll-a fluorescence was enhanced at the edges of filament cores and near 23°S. The turbidity distribution showed comparable patterns.


Fig. 5.1.11 Distribution of chlorophyll-a fluorescence and turbidity at the along-shelf transect (03. - 06.09. 2013).

The filament structure at about 20°S was selected as the study area. The available in situ and remote sensing data suggested that the filament was stable during the entire cruise. This is surprising since filaments were referred as transient structures.

The temporal development of the filament was observed using repeated transects across the filament. The filament covered nearly the upper 100 m of the water column. Figure 5.1.12 depicts the temperature and salinity distribution at three subsequent transects across the filament. Although the temporal variability on smaller scales is high, the general structure of the filament changed only slightly. The cold and less saline filament core is bound by warm saline oceanic waters. The northern front of the filament seems to be much stronger than the southern front.

Fig. 5.1.12 Temperature and salinity distribution at three subsequent transects across the filament. ScanFish data:

upper and middle panel, MSS data: lower panel.

At the same filament transect a series of 64 Microstructure profiles were taken with the MSS profiler at 16 stations. To reduce the impact of intermittency, four subsequent measured profiles were averaged into a mean profile for each station. The aim was to identify hot spots of mixing


across the filament. Fig. 5.1.13 depicts the TKE dissipation rate on the filament transect in the upper 120 m.

Along transect the surface mixed layer outside the filament shows high dissipation rates caused by wind mixing disturbances. Dissipation rates range from 10-7 to 5*10-7 Wkg-1. In the southern filament edge the dissipation is slightly enhanced. In contrast to low dissipation rates at the northern filament edge. Below 40 m depth the dissipation rates was low (10-9 Wkg-1), close to or at the noise level of the instrument. However some hot spots of dissipation were also visible there.

Fig. 5.1.13 Patterns of TKE dissipation rate (contour plot) and density sigmaT stratification (isolines) along the

filament transect down to 300 m depth.

At depths below 100 m some patches of enhanced turbulence were also observed. The transect was located directly over the shelf break. The vertical displacement of isotherms pointed to instability of shoaling internal tides, which enhance the dissipation rates in some locations by an order of magnitude. These patches of enhanced dissipation seem to be confined within sites where the isopycnals were vertically stretched or squeezed.

5.1.4 Phytoplankton (Norbert Wasmund, Arnold De Klerk)

The phytoplankton study carried out at cruise M-100/1 had two aims: 1. As contribution to the NatMIRC monitoring programme, transects at 20°S and 23°S were covered, which consist of stations that are regularly monitored by the NatMIRC. These data improve the monitoring data basis of NatMIRC and serve, at the same time, the investigations of the project GENUS II. The parameters considered were phytoplankton composition and biomass (surface samples) and chlorophyll a concentrations from 4 depths, fractionated for size classes of < 20 µm, 20-200 µm and > 200 µm. Data are not available yet. 2. Work on the tasks formulated in the proposals for the project GENUS II and especially the cruise M100/1. These tasks can be structured into two sub-tasks:


2.1. Routine sampling of phytoplankton parameters [phytoplankton species composition and biomass, chlorophyll a concentration, turbidity (Secchi depth) and at specific stations also primary production and nitrogen fixation] in the station grid. It will give information on the spatial distribution of phytoplankton. Together with oceanographic parameters (TP2) and data on nutrient concentrations (TP4), reasons for uneven distribution of the phytoplankton can be found. Specific patterns are expected in filaments, whose investigation was a prominent topic of this cruise. The phytoplankton basis data are also of interest for other working groups of GENUS (e.g. for food chain investigations by zooplanktologists or for validation of the biological parts of the models). 2.2. Investigations on the influence of mixing processes at the fronts between filament and surrounding water on phytoplankton composition and productivity. Such mixing is simulated by mesocosm (“tank”) experiments, as explained below. The hypothesis was raised that frontal regions are hot spots of productivity. Also the maturation of the filament water can be followed in these tanks. It is hypothesized that a specific phytoplankton succession from diatoms via dinoflagellates to coccolithophores may occur in aging filaments. As the filling stations of the tanks were re-visited at the end of the cruise, the comparison of the tank and the field data can give information whether the filaments have refreshed or matured. Phytoplankton sampling was performed by means of a rosette sampler (combined with CTD). Samples were taken from different depths in order to get representative data from the euphotic zone. The following phytoplankton parameters were investigated: phytoplankton composition and biomass, by qualitative and quantitative microscopic

analyses chlorophyll a analyses primary production, based on 13C incorporation, to be measured by mass spectrometry nitrogen fixation, based on 15N incorporation, to be measured by mass spectrometry primary production and total community respiration, measured by oxygen changes,

analysed by optodes primary production and total community respiration, measured by oxygen changes,

analysed by Winkler titration (TITRINO) Secchi depth as a proxy for water turbidity or phytoplankton concentration. Phytoplankton identifications may be supported by specific methods (e.g. electron

microscopy) based on net samples (“Handnetz” 25 µm), which were taken from 0-20 m depth.

Additionally, the influence of mixing processes at the fronts between filament and

surrounding water on phytoplankton composition and productivity was simulated by mesocosm (“tank”) experiments.

The experimental setup for task 2.2 is shown in Figure 5.1.14. Tanks 1-3 were filled in the centre of the filament (station 1874), tanks 7-9 outside the filament (station 1877), and tanks 4-6 contained a 1:1 mixture of these waters. Tank 10 was reserve. After filling on 08./09.09.2013, the tanks were sampled on 11.09., 14.09., 17.09., 20.09., 23.09. and 26.09.2013.


Fig. 5.1.14 The arrangement of the tanks on deck.

Selected results of the measurement of primary production by means of the optodes are presented in Fig. 5.1.15, showing the relative increase of oxygen concentrations during a five hour incubation. Start concentration is set to 100 %.

Fig. 5.1.15 Oxygen production in bottles filled with waters of tanks 1-9 (tank 9 in two replicates) during a five-

hours incubation on 11.09.2013.

It is evident from Fig. 5.1.16 that oxygen production is linear during the incubation time and that the replicate tanks form groups of very different productivity. On 11.9.2013, two days after filling the tanks, primary production was clearly higher in tanks 4-6, representing mixing at the frontal zone, than in the original waters.

Their high productivity could, however, not be maintained for long, presumably because of nutrient limitation (nutrient data are not available yet). After exhaustion of the nutrients, the production is based on regenerated nutrients. The phytoplankton biomass decreased because of feeding by the developing small zooplankton (copepods). Already after day 3, the productivity decreased to a moderate level, which kept for a longer period due to some kind of equilibrium between primary production and community respiration, i.e. net production approaching zero (Fig. 5.1.16).


Fig. 5.1.16 Development of net community production in the tanks. The three replicate tanks are averaged to one

curve.

5.2 Sub-Project 4 Geo: Biogeochemistry: Carbon and Nutrient Cycling (Anita Flohr, Dieter Peterke, Victor Libuku)

and Reactive Trace Gases (SP 3) (Enno Bahlmann, Ralf Lendt, Caitlin Frame)

GENUS as a multidisciplinary program aims at improving our understanding of the complex interaction between biological, biogeochemical and physical processes within the Benguela upwelling system and their response to environmental changes. Within this framework the subproject TP4-Biogeochmistry aims to study the functioning of the biological pump which is referred to as the uptake of carbon through the photosynthesis of organic matter, the precipitation of calcium carbonate and the subsequent transport of carbon from the surface ocean into the sediments. The biological pump strongly influences CO2 fluxes across the air-water interface and the distribution of dissolved oxygen in the water column. Furthermore it plays an important role for the long-term sequestration of atmospheric CO2 by linking the three major carbon reservoirs, atmosphere, ocean and lithosphere (e.g. McElroy, 1983). Upwelling systems have further been suggested as important source regions for a variety of reactive and radiative active trace gases such as methane but also halocarbons and sulfur bearing compounds. In cooperation with the BMBF project SOPRAN we made a first attempt to study the distribution and isotopic composition of selected trace gases focusing on methane and halocarbons. Aims

Apart from sampling transects perpendicular to the coast, the emphasis of the cruise M100/1 was to study an upwelling filament on the vertically and horizontal scale. Our aims during this cruise were:

1. to determine pH, CO2, CH4 and the carbon stable isotope composition of CO2 and CH4 concentrations in surface water along the cruise track,


2. to measure total alkalinity (TA) and dissolved inorganic carbon (DIC) concentrations in water samples collected along vertical profiles,

3. to take samples for the determination of nutrients (PO43-, NO3

-, NO2-, Si(OH)2), dissolved

organic carbon (DOC) and stable carbon isotope ratios of DIC (δ13C DIC), 4. to take samples for determining the concentration and isotopic composition of

atmospheric and dissolved halocarbons and sulfur bearing compounds, 5. to introduce Victor Libuku, a master student from Namibia, to the above mentioned

methods to contribute to capacity building within the framework of the GENUS project. Methods

Several underway systems for the determination of carbon dioxide (CO2), methane (CH4), isotopic ratios δ13CCO2, δ13CCH4, pH, oxygen (O2), salinity (S) and temperature (T) were installed onboard. These systems were supplied continuously with seawater by an underwater pump, positioned in the moon pool.

The mole fraction of CO2 (xCO2) of surface water and atmosphere was continuously measured by the SUNDANS system (Marianda, Kiel). The system was calibrated every 7 hours by measuring pure nitrogen and 2 different standard gases with mixing ratios of CO2 in air covering the range of the expected pCO2 values. Sea water temperature, salinity, wind speed and the atmospheric pressure were as well constantly recorded by this device. The collected data will be evaluated and used to convert xCO2 to the fugacity of CO2 (fCO2) which is required to calculate the CO2 flux across the sea water interface.

In addition, a cavity ring down spectrometer (PICARRO G2201-i) was coupled to an equilibrator allowing for the first time the underway determination of the mole fraction and isotopic composition of CH4 and CO2 both in the water phase and in the atmosphere. A target gas with known CO2 and CH4 concentrations was measured once a day for later recalibration. The PICARRO G2201-i was further coupled to an AutoMate FX unit for measuring DIC in discrete water samples. For calibration of the DIC analysis certified reference material (CRM, batch #111, provided by A. Dickson (Scripps Institution of Oceanography, La Jolla, CA, USA) was used.

A FERRY BOX system (4H JENA) was installed to record the S, T, O2 and pH in surface water along the cruise track. The S, O2 and pH sensors are stable over long time periods and were maintained and calibrated twice during the cruise.

Vertical profiles were obtained by CTD casts along distinctive cross shelf transects at approximately -17.25°S, -20°S, -23°S and at stations associated with the filament study. Overall about 400 water samples were taken for later analysis on nutrients, DOC and stable isotopic ratio of δ13CDIC. The measurements of TA were performed on board with a VINDTA 3S system (Marianda, Kiel) (Mintrop, 2005) according to standard operation procedure (Dickson et al., 2007). The VINDTA 3S was calibrated using certified reference material (CRM, batch #111, provided by A. Dickson (Scripps Institution of Oceanography, La Jolla, CA, USA)).

A high volume air sampling system and a large volume purge & trap system was installed for discrete sampling of reactive trace gases. A total of 50 air samples and 80 water samples were taken during the cruise whereas the sampling was conducted along the strong biogeochemical gradients in the Benguela Upwelling. These samples will be analyzed for the mole fraction and isotopic composition of selected reactive trace gases using GC/MS-GC-MS/IRMS. The concentration data will be used to assess the air/sea exchange and source strength of the


Benguela Upwelling. The isotopic information will further be used to gain further insights into the production and fate of these compounds. Preliminary results

A pronounced spatial variability was observed in the trace gas concentrations. Generally, highest CO2 and CH4 values were measured along the coast and decreased towards the open ocean. xCO2 maximized to 1450 ppm and xCH4 to 540 ppm off Walvis Bay coinciding with lowest pH and O2 values (Fig. 5.2.1). Along with the low surface temperatures it suggests that an active upwelling event of hypoxic and CO2-laden water was sampled off Walvis Bay which is also supported by the isotopic signature in CO2 and CH4. The δ13CCH4 data suggest a high variability by more than 30‰ with the highest variability showing up off Walvis Bay. Surprisingly, the most enriched δ13CCH4 coincided with the highest methane concentrations suggesting a more pronounced CH4 degradation at these spots. However these are preliminary results still subject to validation.

Fig. 5.2.1 Preliminary results of a) xCO2 (ppm) and temperature (°C), b) O2 (µmol l-1) and pH and c) xCH4

(ppm) and δ13CCH4 (‰) in surface water along a transect parallel to the coast stretching from Kunene (-17.25°S) to Walvis Bay (-23 °S) (19.09.–21.09.2013).


Scan-fish sections were used to characterize the dimension of the filament and the position of

the frontal structures. The results of underway measurements during one of these sections through the filament are shown in Fig. 5.2.3. Here, the fronts of the filament are evident from a drop in temperature reaching a minimum at the center that was characterized by a maximum in xCO2 and a minimum of O2 at ~20°S. The O2 increase at -20.5°S suggests intense primary production but might as well be a temperature effect. However, the results of trace gas concentrations still have to be corrected and complemented by the meteorological background data before assumptions on the relative contribution of physical and biological processes can be made.

Fig. 5.2.2 Preliminary results of the surface expression of the filament as observed in a) xCO2 (ppm) and

temperature (°C) and b) O2 (µmol l-1) and pH during a scan fish cross section (06.09.–07.09.2013) (also refer to the report of TP2).

The TA was measured on board but further interpretation of the results is not possible because

the values still have to be corrected for the salinity. Additionally, the DIC samples could not be measured onboard during M100/1 due to a malfunction of PICARRO G2201-i in combination with the AutoMate autoanalyzer unit. Hence, no further characterization of the carbonate system with respect to the vertical structure is possible yet.

Victor Libuku about his impressions during M100/1: “As a Namibian doing research in the Benguela was a privilege and an honor for me and working with people who are experienced and knowledgeable on the Benguela system was a rare and much appreciated opportunity. The cruise was very helpful to me as I learnt to operate numerous instruments used in research and I had a firsthand experience of what research is all about in the field. I learnt how to use the PICARRO G2201-i which measures atmospheric and oceanic CO2 concentrations, as well as the


SUNDANS which measures also atmospheric and oceanic CO2 concentrations. Another instrument I learnt to use was the VINDTA 3S which is used to measure ocean alkalinity by using an acid titration method. All this instrumentation I learned how to use on the M100/1 cruise and will have a greater positive impact on my future in science and research especially in the Benguela system where I as a Namibian intend to work after my studies. I also did not only learn how to use instruments but also how to properly collect and fix samples for total alkalinity measurements, dissolved inorganic carbon, dissolved organic carbon, as well as nutrients. I learnt also that at sea cohesion and team work are the order of the day and that organization and planning are important to ensure good research and collection of usable valuable data.”

Nitrous oxide (N2O) is a long-lived greenhouse gas that is now the third largest contributor to radiative forcing (WMO, 2011). Microbially-mediated nitrogen cycle transformations in soils and in the ocean are the dominant source of N2O. Application of nitrogen-based fertilizers has caused atmospheric N2O concentrations to rise steadily for the past 200 years, so that the current N2O concentrations are 20% higher than preindustrial concentrations (Machida et al., 1995). Although the total anthropogenic source is relatively well constrained by the atmospheric lifetime of N2O and the increase in atmospheric concentration (Huang et al., 2008), large uncertainties remain in the partitioning between terrestrial and marine sources and the underlying biogeochemical controls on microbial N2O production.

In the Namibian upwelling region, winds drive coastal and offshore upwelling that draw old, deep N2O up to the surface and make the region a hotspot for N2O release to the atmosphere. Upwelling also stimulates production of new N2O as upwelled nutrients fuel enhanced primary production and associated remineralization processes. Research during M100-1 investigated key biogeochemical variables and biological processes that influence production rates of N2O in the Benguela/Angola upwelling system. To this end, water samples were collected for dissolved N2O concentration and isotopic/isotopomeric measurements along zonal transects at 23°S, 20°S, and 17.3°S. Furthermore, seawater incubations with 15N-labeled tracers were conducted at 23°S to identify the specific biological processes responsible for N2O production and estimate their rates as several geochemical parameters, such as oxygen (O2) concentration, were varied. These experiments were aimed at developing a better understanding of how N2O production and consumption rates may respond to future geochemical changes in the upwelling system.

5.3 Sub-Project 4 Bio: Ichthyoplankton Studies (Simon Geist, Josefine Edward) Abundance and condition of early life stages determine recruitment success and by this the size of fish stocks. Aligned to preceding GENUS cruises during 2008-2011, the ichthyoplankton work during cruise M100-1 focused on the collection of fish larvae during the high upwelling season in the northern Benguela to describe horizontal and vertical distribution patterns of fish larvae and their condition and growth under different environmental conditions, continuing the GENUS time series. The second aim was to sample an upwelling filament (core, frontal zones, outside) to determine small-scale differences in ichthyoplankton abundance, species composition and nutritional condition; as well as to contribute to the joint effort to set up a stable isotope food-web of an upwelling filament structure. The third aim was to introduce Josephine Edward,


a junior scientist from NatMIRC, Swakopmund, into ichthyoplankton research methods and identification of fish larvae.

Ichthyoplankton collections were made at stations on the shelf and slope up to water depths of 3000 m. Two different nets were used to catch fish eggs and larvae: an obliquely towed Multinet (MNobl, Fig. 5.3.1) and a Tucker Trawl (TT). The Multinet (HYDROBIOS, type Midi: 0.25 m2

mouth area) was equipped with five nets of 500 μm-mesh size, temperature and oxygen probes, and an inner and outer flow meter to monitor the net’s trajectory (for volume filtered calculations) as well as net clogging (Fig. XX.1). It was towed obliquely at 21 stations, in five different depth strata (Table XX.1). The upper two nets were equipped with small net inlays (mouth diameter of 12 cm and 55 μm mesh size) to simultaneously catch potential food organisms of the fish larvae. The TT has an effective mouth area of 1 m2; two mesh sizes were used: 1000 and 1550 μm. Its opening/closing mechanism allows the collection of larvae in a targeted depth stratum of the water column. A total of 7 TT hauls were made within the upper 70 m of the water column to collect larger quantities of fish larvae. Both nets were handled over the side, towed horizontally at 1.5 knots. All samples were screened for their content of fish larvae. Live larvae were transferred to a temperature controlled cultivation fridge, simulating in-situ

temperature. Dead fish larvae were sorted out, measured for standard length and immediately frozen to -80°C for subsequent determination of condition and tropic analysis at ZMT, Germany. All remaining MNobl samples were preserved in buffered formalin (4% in seawater) for quantitative community studies, which are part of a more than ten years long time series. In total 748 fish larvae were sorted out, identified and frozen for subsequent analysis (Fig. 5.3.2). Similar to the D356 spring cruise, total larval abundance was low compared to cruises conducted during

summer (February 2011, March 2008). Larvae of different mesopelagic species (Fig. 5.3.3a) dominated the ichthyoplankton community during the cruise (Table 1). Black bellied rosefish (station #1877, Fig. 5.3.3b), Goby (#1921, Fig. 5.3.3c) and hakes (#1920, Fig. 5.3.3d ) were caught in considerable numbers at single stations, with the latter two species mainly occurring at stations with shallow water depths (<200 m). In contrast, Cape horse mackerel, sardine and anchovy larvae were almost completely absent and only caught in small numbers (Table 5.3.2). They were caught at few stations situated further offshore

than the areas where they are usually caught during the low upwelling season in summer. Most larvae were smaller than 10 mm in standard length. During the cruise, six Helicolenus – larvae could be caught alive and were transferred to NatMIRC laboratory in Swakopmund for further experiments after the cruise. Sampling the filament, eggs and larvae were rare in its core (station #1874), with a few goby and mesopelagic larvae caught. In the frontal zones (#1876 & 1894) large numbers of fish eggs and some goby and mesopelagic larvae were present. The highest

Fig. 5.3.1 The Multinet returns (Foto: Ralf Lendt)

Fig. 5.3.2 Screening for fish larvae (Foto: Lindan Mlambo)


abundance and species richness of fish larvae was found at stations adjacent, but outside the filament (#1877 & #1895).

Josephine Edward about aim no.3: “During the cruise I have learned how fish larvae species look and how to identify them by distinguishing features such as pigmentation (melanophores and photophores). I have gained hands on knowledge on how to operate the MNobl and the TT, these are the sampling techniques used to catch fish larvae. I also learned the different preservation methods used to preserve fish larvae samples either in formalin or in a -80°C freezer. Finally, I learned some basic fish keeping techniques used to keep live fish larvae for experiments.” Tab. 5.3.1 Oblique Multinet casts during M100-1 Haul No. Ship station Date Lat. (S) Long. (E) Water depth (m) 1 1863 01.09.2013 23°00 14°14 115 2 1864 01.09.2013 23°00 14°02 130 3 1874 08.09.2013 20°04 11°58 353 4 1876 08.09.2013 20°21 12°06 313 5 1877 09.09.2013 20°48 12°22 412 6 1894 11.09.2013 19°56 11°54 368 7 1895 11.09.2013 19°30 11°40 368 8 1900 13.09.2013 20°36 11°45 1019 9 1906 15.09.2013 20°00 12°20 212 10 1912 18.09.2013 18°00 11°41 117 11 1914 18.09.2013 17°18 11°30 146

Fig. 5.3.3 Examples of fish larvae caught during M100-1: a) Mesopelagic (Diaphus sp.), b) goby (Sufflogobius bibarbatus), c) hake (Merluccius sp.) d) Mesopelagic (Bathylagus sp.) e) Rosefish (Helicolenus dactylopterus)


Haul No. Ship station Date Lat. (S) Long. (E) Water depth (m) 12 1915 19.09.2013 17°18 11°21 325 13 1920 23.09.2013 23°00 13°45 143 14 1921 23.09.2013 23°00 14°02 134 15 1923 23.09.2013 23°00 13°18 360 16 1924 24.09.2013 23°00 12°48 895 17 1925 25.09.2013 23°00 11°48 2902 18 1931 28.09.2013 19°36 11°42 370 19 1932 28.09.2013 19°59 11°55 359 20 1934 29.09.2013 20°27 12°09 333 21 1935 29.09.2013 21°11 12°32 432 Table 5.3.2 Presence of fish larvae taxa at sampling stations

stat

ion

#

fish

eggs

Clu

peid

ae

Car

angi

dae

Mer

lucc

iidae

Gob

iidae

Scor

paen

idae

Sole

idae

Gem

pylid

ae

Spar

idae

Con

grid

ae

Mel

amph

aida

e

Ble

nniid

ae

Mes

opel

agic

sp

ecie

s 1874 x x x x 1876 x x 1877 x x x x 1894 x 1895 x x x x x x 1898 x x 1900 x x x 1905 x 1906 x x x 1912 x x x 1914 1915 x x x 1920 x x x 1921 x x x 1922 x 1923 x 1924 x x x 1925 x x x x 1930 x x x x x 1931 x x x x 1932 x x x 1933 x x x 1934 x x x x 1935 x x


5.4 Sub-Project 5: Micro- and Mesozooplankton, Sampling and ROV Deployments, Benthos Sediments

(Rolf Koppelmann, Bettina Martin, Karolina Bohata, Jörg Bruhn, Bronwen Currie) Zooplankton organisms are important for the transfer of organic material from primary producers into higher trophic levels and into greater depths; and they play an important role for the re-mineralization of organic matter (Robinson et al. 2010). The main goals of the GENUS subproject 5 during Meteor cruise 100/1 were to examine the horizontal and vertical distributions of different groups of micro-, meso- and macrozooplankton related to upwelling filaments, their trophic role, and their contribution to the oceanic carbon cycle in the high productive Benguela upwelling region. The variability of these processes and the involvement of different zooplankton groups will be assessed in the GENUS project. Several vertical hauls were taken inside, outside and in the front of an upwelling filament with a multiple closing net (HYDROBIOS; mesh aperture 300 µm) in addition to horizontal sampling with a 1 m² Double-MOCNESS (Multiple Opening and Closing Net and Environmental Sensing System, Wiebe et al. 1985; mesh aperture 330 µm) at transects across the fronts of the filament.

A synoptic sampling of the mesozooplankton in the northern Benguela was performed with the 1 m² Double-MOCNESS to analyse the role of different zooplankton groups for biogeochemical and ecological processes in the region. This is part of time-series sampling already performed in March/April 2008 (RV MARIA S. MERIAN), December 2009 (FRS AFRICANA), September/October 2010 (RRS DISCOVERY), and January/March 2011 (RV MARIA S. MERIAN). Little is known so far about the contribution of microzooplankton to the pelagic remineralisation and its general role in the food web. The sampling of this faunal element started in February 2011 and was continued during RV METEOR cruise M100/1. Samples were taken with water bottles and multinets (55 µm mesh size). Part of the organic material produced in the water column sinks to the bottom. To study the epibenthic zooplankton fauna horizontal near bottom-sampling (5 meters above bottom) was done on the shelf and slope on the Kunene River and Walvis Bay transects with the multiple-closing-net equipped with an altimeter. Planned surveys of the sediment structure and the benthic megafauna with a remotely operated vehicle (ROV) were not completed due to technical problems and bad weather conditions (Table 5.4.1).

Table 5.4.1 ROV deployments

Station No Date Start Time UTC

End Time UTC

Coordinates Water Depth

[m] Remarks

1912-6 1 18.09.13 06:45 07:15 17°59.9'S, 11°40.8'E 115 ROV failed due to water

intrusion at surface

1915-10 2 19.09.13 06:20 06:50 17°18.0'S, 11°20.9'E 326 ROV failed due to water

intrusion at 10 m depth

1921-7 3 23.09.13 07:58 09:20 22°59.9'S, 14° 3.2'E 132

ROV failed after 1h due to water intrusion at 130

m depth

1927 4 27.09.13 07:10 07:25 19° 5.1'S, 11°24.36'E 493

ROV failed due to water intrusion at 3 m depth


Microzooplankton sampling and experiments

Microzooplankton organisms are defined as organisms <200 µm in this study (see Sieburth et al. 1978) and consist of Protozoa and small Metazoa. These organisms are important in pelagic food webs. Until now they have been investigated only sparsely in the Namibian Upwelling Region despite their importance for the microbial loop and their potential relevance as food for larger zooplankton.

Water samples for analyses of protozoa, mainly ciliates, were collected with a CTD on the Walvis Bay transect (5 stations) and Kunene River transect (2 stations) in three different depths (surface, 20 m and 40 m). Additionally, stations at the southern and northern front of the filament as well as inside and outside (south) the filament were sampled (Table 5.4.2). Depending on the depth of the sample, between 200 ml and 500 ml of seawater were fixed with acidic Lugol’s solution (84 samples). All samples were kept in darkness at 5°C for further analyses in the home laboratory.

Microzooplankton and small mesozooplankton (up to 300 µm) were collected by vertical hauls in five depth intervals (max. haul depth: 100 m) using a multiple-closing-net with a mesh size of 55 µm (Table 5.4.3). All material was preserved in a 4% formaldehyde-seawater solution buffered with sodium-tetraborate. During the filament study, samples for stable isotope analyses were also taken using the multiple-closing-net. These samples were kept frozen at -80°C.

Experiments for estimating the rates of microzooplankton grazing on primary producers were undertaken using the dilution technique following Landry and Hassett (1982). Water (30 l) for experiments was collected at the surface of some stations using NISKIN bottles (CTD) and gently siphoned through a 200 µm mesh to remove mesozooplankton (Table 5.4.2). Water for the dilution series was filtered through WHATMAN GF/C glass fiber filter (0.2 µm). A duplicate series of dilutions (100, 80, 60, 50, 40 and 20 %) was prepared by gently combining the siphoned water and the 0.2 µm filtered seawater. The bottles were incubated for 24 h at in situ light and temperature conditions. The incubator was equipped with a rotating wheel to keep particles from settling. Triplicate subsamples were taken from all dilution levels at the beginning and at the end of the experiment for the measurement of initial chlorophyll concentrations. The subsamples were filtered onto 25 mm WHATMAN GF/C glass fiber filters and stored in dark at -80°C for further analyses which will be undertaken in the home laboratory.

Table 5.4.2 Water samples from CTD for microzooplankton analyses; Experiment = water for the experimental set up

Station No. Date Lat. Long. Experiment

1862 01.09.2013 23°00 14°20

1863 01.09.2013 23°00 14°14

1864 01.09.2013 23°00 14°03 Exp. No. 1

1865 02.09.2013 23°00 13°52

1866 02.09.2013 23°00 13°41

1867 02.09.2013 23°00 13°31

1868 02.09.2013 23°00 13°20

1869 02.09.2013 23°00 13°08

1874 07.09.2013 20°04 11°58 Exp. No. 2


Station No. Date Lat. Long. Experiment

1876 08.09.2013 20°21 12°07

1877 09.09.2013 20°48 12°22 Exp. No. 3

1892 10.09.2013 19°30 11°40 Exp. No. 4

1894 11.09.2013 20°03 12°00

1895 11.09.2013 19°30 11°40

1898 13.09.2013 20°30 11°44

1906 15.09.2013 20°00 12°20 Exp. No. 5

1909 17.09.2013 20°00 12°52 Exp. No. 6

1914 18.09.2013 17°18 11°30

1915 19.09.2013 17°18 11°21

1916 19.09.2013 17°18 11°12

1920 22.09.2013 23°00 13°45

1921 23.09.2013 23°00 14°02

1922 23.09.2013 23°00 13°08 Exp. No. 7

1924 24.09.2013 23°00 12°48

1925 25.09.2013 23°00 11°48 Exp. No. 8

Table 5.4.3 Multinet samples for microzooplankton and small mesozooplankton analyses; F = samples fixed in

formaldehyde solution, SI = samples frozen (-80°C for stable isotope analyses

Haul No. Ship station Date Lat. Long. F/SI

1 1864 01.09.2013 23°00 14°03 F

2 1874 08.09.2013 23°00 14°03 SI

3 1874 08.09.2013 20°04 11°58 F

4 1876 08.09.2013 20°21 12°08 SI

5 1876 08.09.2013 20°21 12°08 F

6 1877 09.09.2013 20°48 12°22 SI

7 1877 09.09.2013 20°48 12°22 F

8 1877 09.09.2013 20°48 12°22 F

9 1877 09.09.2013 20°48 12°22 F

10 1894 11.09.2013 19°56 11°54 SI

11 1894 11.09.2013 19°56 11°54 F

12 1895 11.09.2013 19°30 11°40 SI

13 1895 11.09.2013 19°30 11°40 F

14 1898 13.09.2013 20°36 11°44 SI

15 1898 13.09.2013 20°36 11°44 F

16 1906 15.09.2013 20°00 12°20 SI

17 1906 15.09.2013 20°00 12°20 F

18 1914 18.09.2013 17°18 11°30 F

19 1915 19.09.2013 17°18 11°21 F

20 1920 23.09.2013 23°00 13°45 F


Haul No. Ship station Date Lat. Long. F/SI

21 1921 23.09.2013 23°00 14°02 F

22 1922 23.09.2013 23°00 13°08 F

23 1923 23.09.2013 23°00 13°18 F

24 1924 24.09.2013 23°00 12°48 F

25 1925 25.09.2013 23°00 11°48 F

Synoptic mesozooplankton sampling

Like in former years (2008, 2009, 2010, 2011), mesozooplankton were sampled at two main transects, off Walvis Bay and off the Kunene River mouth, to obtain a synoptic picture of the composition and distribution of the main taxonomic groups of the mesozooplankton.

The 1 m² Double-MOCNESS is equipped with 18 nets with a mesh size of 330 µm. The nets can be opened and closed sequentially. The volume filtered by each net is calculated from a flow-meter mounted in the net system’s mouth. The sampling intervals on this cruise were 25 m in the top 50 m, 50 m down to 100 m, and 100-200 m at greater depths. On the Kunene River transect two samples (shelf and shelf-break) were taken (Table 5.4.4). No samples were taken further offshore since the vessel had to teturn to port due to a medical emergency. Four stations were examined on the Walvis Bay transect (shelf, shelf-break, slope, oceanic).

Upon recovery of the MOCNESS, the nets were rinsed with seawater and subsamples of the right nets were frozen at -80°C for subsequent stable isotope analyses. The left nets were preserved in a 4% formaldehyde-seawater solution buffered with sodium-tetraborate for future taxonomical and biomass analyses.

Quantification and qualification of major zooplankton groups will be undertaken in the home-laboratory, as well as stable isotope analyses of N and C for further insights in the food web structure. Migrating taxa will be determined and quantified and certain zooplankton groups will be studied more intensively concerning their abundance, composition, distribution, predation pressure and level in the food web.

Table 5.4.4 Sampling data of Double-MOCNESS hauls. WB = Walvis Bay transect, KR = Kunene River transect

Haul Station# Date Start Time UTC

Water Depth

[m] Region Sample intervals

[m depth]

1 1875 08.09.13 08:52 320 Filament, onshore

front south Horizontal in 30 m

2 1893 11.09.13 00:45 370 Filament, onshore

front north Horizontal in 20 m

3 1899-1 13.09.13 13:40 1040 Filament, offshore

front noth Horizontal in 20-25 m 4 1914-7 18.09.13 18:30 150 KR shelf 100-50-25-0 5 1915-11 19.09.13 07:30 335 KR shelf-break 300-200-100-50-25-0 6 1921-10 23.09.13 10:41 130 WB shelf 100-50-25-0 7 1923-2 23.09.13 23:15 360 WB shelf-break 300-200-100-50-25-0 8 1924-10 24.09.13 17:40 950 WB slope 800-600-400-300-200-100-50-25-0 9 1925-6 254.09.13 08:50 2890 WB oceanic 1000-800-600-400-200-100-50-25-0


Mesozooplankton filament sampling

Mesozooplankton were sampled outside, inside, and at the fronts of the detected filament, following directly the mapping that was done by the physical oceanography group. Vertical fine-stratified sampling was obtained by multiple-closing-nets with a mesh aperture of 300 µm down to 380 m, accompanied by horizontal MOCNESS hauls across the northern and southern fronts of the filament (Tables 5.4.4 and 5.4.5). After recovery of the gear the samples were preserved immediately in a 4% formaldehyde-seawater solution buffered with sodium-tetraborate for future biomass and taxonomical analyses. Table 5.4.5 Sampling data of Multinet hauls (300 µm) for mesozooplankton analyses. ab = above bottom

Haul Station# Date Start Time UTC

Water Depth

[m] Region Sample intervals

[m depth]

1 1874-11 08.09.13 03:10 353 Filament center 320-200-100-50-25-0 2 1876-2 08.09.13 16:00 318 Filament, front south 300-200-100-50-25-0 3 1877-13 09.09.13 10:10 411 Filament, outside south 380-200-100-50-25-0 4 1894-9 11.09.13 11:05 363 Filament, front north 330-200-100-50-25-0 5 1895-5 11.09.13 16:57 367 Filament, outside noth 330-200-100-50-25-0 6 1898-9 13.09.13 11:44 1043 Filament, offshore center 330-200-100-50-25-0 7 1906-5 15.09.13 06:53 211 Filament, onshore center 180-100-75-50-25-0 8 1912 18.09.13 09:15 115 Mooring station 5-6 m ab (4 nets)-0 towed 9 1914-4 18.09.13 16:20 147 KR shelf 5-6 m ab (4 nets)-0 towed

10 1915-13 19.09.13 11:17 330 KR shelf-break 5-6 m ab (4 nets)-0 towed

11 1916-5

19.09.13 14:40 828- 776 KR slope

5-6 m ab (2 nets) towed 500-150-0

12 1920-6 23.09.13 00:00 144 WB outer shelf 5 m ab (4nets)-0 towed 13 1921-11 23.09.13 11:39 134 WB inner shelf 5 m ab (4nets)-0 towed 14 1923-3 24.09.13 00:26 360 WB shelf-break 5 m ab (4nets)-0 towed 15 1924-9 24.09.13 15:20 906 WB slope 5-8 m ab (4 nets)-0 towed 16 1931-4 28.09.13 08:58 367 Filament, outside north 300-200-100-50-25-0 17 1932-5 28.09.13 17:25 360 Filament, front north 300-200-100-50-25-0 18 1934-2 29.09.13 03:16 330 Filament center 300-200-100-50-25-0 19 1935-4 29.09.13 12:06 431 Filament, outside south 300-200-100-50-25-0

Near-bottom mesozooplankton sampling

Near-bottom zooplankton are an important link between the upper water column and the benthos (see Christiansen et al. 1999). Moreover, they may help to investigate the off-slope transport of organic matter from the shelf into the deep-sea. We equipped the multiple-closing-net with an echo-sounder to measure the distance to the bottom. The nets were towed at 1.5-2 knots with a distance of approximately 5 m above the bottom. Four hauls at depths between 115 and 906 m were taken on the Kunene and Walvis Bay transects, each (Table 5.4.5). The samples were preserved immediately in a 4% formaldehyde-seawater solution buffered with sodium-tetraborate for future taxonomical and biomass analyses.


Sediment Benthos (Bronwen Currie) Benthic fauna of the Namibian shelf have not yet received focused or dedicated study. Opportunistic sampling over the last few years has however been valuable in providing an overview of the benthic environment and the types of animals found. Along the central coast a consistent organic-rich food supply rains down to the sea bottom, but there are other factors for the animals that live there to contend with: community structure is likely primarily structured by a balance between plentiful food, little or no oxygen and sometimes hydrogen sulphide. Sediments are soft and contain varying amounts of shell debris.

Deep benthic animals in low-oxygen environments are typically tiny. Ideally sampling should be carried out by multiple-drop multicoring, with concurrent biogeochemical investigations made from porewater profiles; however no coring was possible on this cruise so a Van Veen grab was used to take bulk qualitative samples. It must be appreciated that a grab will often “blow” away small surface organisms. Van Veen grab samples were taken from 21 stations on the shelf, shelf-edge and slope to a depth of approximately 400 m (depth limited by cable limit). Samples collected were:

1. whole bulk sediment preserved with buffered formalin 2. subsample sieved fresh to 300 µm for “quick-look” inspection, particularly for large

sulphide oxidizing bacteria (which do not preserve well) and obvious faunal groups present

3. small subsamples fresh-frozen for analysis of physical properties and heavy metals

Inspection of fresh samples collected between latitudes 20⁰S to 24⁰S confirmed that the central inner shelf is sparsely inhabited by small-sized animals: only those adapted to severely low bottom oxygen and sulphidic conditions are able to exploit the abundant organic food supply. Large sulphide-oxidizing bacteria Thiomargarita namibiensis and Beggiatoa spp. were found at stations where hydrogen sulphide is known to be plentifully available (H2S cannot be properly measured from grab sediment). In a transitional zone between approximately 150m to 200m water depths a firmer dark green surface mud is found, that is more sandy and contains shell debris. The bulk grab samples smell sulphidic but there are probably several centimeters of sulphide-free sediment in the surface layer, as evidenced by longer and larger in-fauna – notably robust tubeworms, and the scanty presence of Thiomargarita and mobile filamentous large sulphide-oxidizing bacteria Beggiatoa and Thioplaca. Faunal diversity in phylum and taxon number appears to rapidly increase in these stations, probably due to enhanced habitat niches of less oxygen stress coupled with plentiful particulate food supply. Polychaetes dominate the macrofauna, whilst nematodes are particularly abundant in the meiofaunal component. Pronounced large-shell debris (as opposed to shell grit which occurs commonly) presented at some of the sampled stations. From depths of 300m and deeper the character of the sediment changes to ochre-coloured mud, and phyla diversify to include more coelenterates (seapens and solitary anemones), crustaceans and echinoderms. Increased bioturbation is apparent from the long tubes.


The stations sampled in the northernmost stations between 17 ⁰S and 18⁰S showed a different community pattern: although the fine textured soft dark mud of the shallow stations obviously contained H2S (smell) the fauna were dominated by molluscs with several crustacean taxa present, and large sulphide-oxidizing Thioplaca were consistently found. Table 5.4.6 Sampling data of Van Veen grab

Station No. Meteor

Depth m.

Bottom DO ml/L (CTD raw data)

Sediment Sulphide-oxidizing bacteria*

Quick-look faunal groups

1862 61.4 0.17 dark green-black ooze Thm, Begg not yet inspected



1866 147.4 0.69 dark mud and shell

Begg, Thpl, Thm Polychaetes, oligochaetes, nematodes

1867 221 0.77 dark fine sandy, shell grit not found Pennatulacea, bivalves, polychaetes

1868 347 0.82 dark ochre clay-sand, shell remains

not found Polychaetes, nematodes,

1874 357.8 0.76 dark ochre clay-sand not found Polychaetes, nemertean, molluscs,

nematodes

1876 313.2 0.48 dark ochre mud not found poychaetes, macrurid, amphipod, alcyonarian, nemerteans, nematodes

1877 412 0.92 dark ochre mud not found Polychaetes, copepods, bivalves, isopod, nemertean, nematodes, bivalves

1895 366.5 0.63 dark ochre sandy mud not found Polychaetes, bivalve, nematodes

1906 212 0.74 dark mud Thpl, Begg not yet inspected

1907 148 1.25 dark mud Thm, Begg, Thpl Polychaetes, nematodes

1908 138 0.83 dark mud thm not yet inspected

1912 115 1.36 dark mud Thm, Begg, Thpl

Bivalves, gastropods, amphipods, cumacean, polychaetes, nematodes

1913 54 1.74 dark black-green mud Begg

Bivalves, gastropods, polychaetes, various crustaceans including hermit crabs & cumaceans

1914 147.2 0.85 dark fine-grain mud Thpl, Begg Bivalves, alcyonarian, polychaetes,

amphipods, nematodes 1915 326 0.58 dark ochre mud not found Polychaetes, ophiuroid

1917 180 0.49 dark mud Thm, Begg, Thpl

Polychaetes, nematodes, nemertean, alcyonarian, bivalves

1918 204 0.51 dark mud and shell Begg, Thpl Polychaetes, nematodes, nemertean,

alcyonarian

1919 300.3 0.9 dark ochre mud not found Polychaetes, alcyonarian, actinaria, ophiuroids, echinoid, nemtodes, pennatulacea

1922 314 0.84 yellow ochre clay-mud not found Pennatulacea, actinaria, polychaetes,

nemertean, bivalves

*Thm = Thiomargarita namibiensis; Begg = Beggiatoa spp.; Thpl = Thioplaca sp.


5.5 Sub-Project 6: Distribution and Physiology of Calanoid Copepods in an Upwelling Filament and in Relation to the Oxygen Minimum Zone in the Northern Benguela System

(Anna Schukat, Marina Giunio) Copepods are major components of mesozooplankton communities in coastal upwelling areas with key species representing major trophic links between primary production and higher trophic levels (Loick et al., 2005; Verheye et al., 2005). Furthermore, copepods play a crucial role in the cycling of organic matter in the ocean, e.g. via moulted exoskeletons, faecal pellets, and respiration processes (Al-Mutairi and Landry, 2001; Dam et al., 1995; Steinberg et al., 2008). In the Benguela Current, upwelling filaments typically form on the fronts of the upwelling cells where the upwelling is well developed (Lutjeharms et al., 1991). These filamentous bands are usually between 100 and 500 km wide (Lutjeharms et al., 1991). Biological processes in general and the role of zooplankton species in particular within upwelling filaments are poorly understood. Therefore, one focus of subproject 6 on this cruise was to investigate the distribution and physiology (e.g. metabolic activity, feeding preference, trophic level) of dominant copepod species in different structures of an upwelling filament.

Additionally the community structure and metabolic activity of copepods in low oxygen water were investigated. Oxygen minimum zones (OMZ) are a common feature of the northern Benguela system and may influence zooplankton metabolic processes and vertical distribution and thus the structure of zooplankton communities.

In effort to better determine zooplankton biodiversity, single-gene sequencing will be conducted on samples collected during this cruise in collaboration with AZTI-Technalia, Spain and KAUST, Saudi Arabia. This developing method will provide insight into species richness in bulk samples, as well as determination of species-specific sequences. Physiological response to low oxygen can be investigated via transcriptomics, which is another scope of this research.

Mesozooplankton was sampled by the team of subproject 6 during preceding cruises in the Benguela Current on board RV MARIA S. MERIAN (2008), FRS AFRICANA (2009), RRS DISCOVERY (2010) and MARIA S. MERIAN (2011). To complement the existing data sets, the sampling program was continued on this cruise. Copepod Sampling and Experiments

Mesozooplankton were collected by stratified vertical hauls with a MULTINET MIDI (HydroBios, Kiel, Germany; mouth opening: 0.25 m2: mesh size: 200 µm). Five stations at the Walvis Bay line (23°S), two at the Kunene line (17°S) and three stations in between (19°S) were sampled. Maximum sampling depth was close to the seafloor at onshore stations and over the shelf or 1000 m for offshore sampling. A set of five discrete depth layers was sampled in one haul. At stations with a pronounced OMZ (oxygen concentration less than 1.5 ml O2 l-1), two consecutively hauls were conducted. One of the hauls was preserved in ethanol (98%) for genetic community analyses and the other haul was used to sort out copepods in good condition for respiration experiments on board and for enzyme activity (Electron transport system) measurements in the home lab. The remains of the samples were preserved in a 4% formaldehyde-seawater solution for later analyses of mesozooplankton abundance, biomass, vertical distribution and species composition.


In case of the filament study the maximum sampling depth was 180 m. Sampling depth intevals were adjusted to the other subprojects of GENUS (180-120 m, 120-100 m, 100-80 m,

Fig. 5.5.1 Experimental set-up of the 10-channel fiber-optic oxygen meter.

80-20 m and 20-0 m) for a better comparison of data. The filament was sampled on two

transects (eastern transect: 5 stations: north outside, northern front, centre of filament, southern front and south outside; western transect: 1 station: centre of filament). An additional station was sampled onshore (20°0’S, 12°2’E) for the comparison of the zooplankton community in the upwelling filament and in the coastal upwelling area. After 15 days the eastern transect of the filament was sampled again with 4 stations (north outside, northern front, centre of filament, southern front) to investigate the succession in the filament.

Animals for respiration measurements and stable isotopes were sorted out to determine the condition of species and the food web structure within the filament.

Respiration rates of different copepod species were measured on board by optode respirometry (Köster et al., 2008) with a 10-channel optode respirometer (PreSens Precision Sensing Oxy-10 Mini, Regensburg, Germany) in a temperature controlled refridgerator (Fig. 5.5.1) under in situ conditions (i.e. oxygen concentration and temperature). The incubation of specimens during experiments was performed in small 10 ml gas-tight glass bottles. For each set of experiments, two animal-free controls were measured under exactly the same conditions to compensate for potential errors. Depth profiles of temperature derived from the CTD sensor at each station were used to set the refridgerator to the ambient temperature at sampling depth. Low oxygen seawater (> 1 ml O2 l-1) was taken from CTD water samplers. In total, 19 respiration measurements were conducted with around 10 calanoid copepods species which sum up to more than 150 individual respiration measurements. After the experiments, all specimens were deep-frozen at -80°C for later dry-mass determination in the home lab.


Preliminary results of this cruise can only be given of the general distribution of copepods for the filament study (Fig. 5.5.2). All other data will be analysed after the cruise. The highest biomass of copepods was found in the centre of the filament. Females of Calanoides carinatus dominated the copepod biomass, followed by females of Metridia lucens. The species composition at the

northern front of the filament as well as at the north outside station was different as compared to the species composition at the southern margin of the filament. High densities of phytoplankton and low biomasses of mesozooplankton were found in the north. In contrast, phytoplankton biomass was low in the south (Fig. X.2). The copepod com-position in surface waters (20-0 m) also differed between the frontal zones; Metridia lucens was the dominating copepod species at the northern front, whereas Eucalanus spp. were the most abundant species at the southern front. Aetideus armatus was common in both frontal zones at depths between 100 m and 180 m.

The influence of the OMZ on the vertical migration and on the physiology of chosen copepod species will further be analysed in the home lab.

5.6 Sub-Project 7: Krill as Indicators of Environmental Variation and as Pivotal Components of the Plankton of the Northern Benguela Current System

(Thorsten Werner, Lindan Mlambo ,Cornelia and Friedrich Buchholz) The GENUS project with determinations of primary and secondary production is an excellent background to elucidate the hydro-climatic situation in the food web of the research area (Huenerlage and Buchholz, 2013). The particularly short food chain of krill secures it an indicator function in the integrative modelling approach. Physiological studies of euphausiid key species are part of the project’s analysis of key rates of physical, biogeochemical and biological ecosystem components and to energy flows and feedback of trophic structures on biogeochemical cycles. The specific objective of the cruise was to focus on krill within smaller scale processes along and across upwelling filaments and associated boundary zones.

The major part of the sampling relied on the “krill-net”, i.e. a MOCNESS (Multi Opening and Closing Net with Environmental Sensing System, Wiebe et al. 1985), optimized for catch of fast swimming macro-zooplankton which avoid smaller nets, with 9 nets (1 m² mouth) of soft fabric and with large mesh-size (2mm) equipped with soft cod ends for careful catch (Fig. 5.6.1).

Fig. 5.5.2 Illustration of sampling vials within the filament, at the fronts and outside the filament.


Twenty three MOCNESS hauls were performed in depth-discrete steps, i.e. single nets opened and closed at pre-determined depths from up to 1000 to 0 m at night and day to differentiate vertical positioning of target species. Krill was counted in the net samples, and residence depths noted. Individuals were isolated and maintained in ambient cooled water until species, size and sex were determined. Additionally, in Euphausia hanseni moult rate, sexual development stage, visual lipid stages and mid-gut gland colour were scored to assess their adaptive capacity. Samples were shock-frozen for later determination of stable isotopes and biochemical composition.

A strongly developed upwelling filament at

approx. 20°S was chosen for intensive study. The filament persisted and was re-sampled towards the end of the cruise. Initially, ten net catches targeting euphausiids were conducted to investigate small scale differences in physiological performance and biomass of krill across the filament. Two additional coastal stations served as reference. Sampling was done at night at fixed depth intervals in accordance with the sub-projects SP4-Bio, SP-5 and SP 6 (180-120 m, 120-100 m, 100-80 m, 80-20 m and 20-0 m). These depth intervals ensured a high-resolution at boundary zones pre-determined by the hydrographic investigations done by SP-2. Three day to night hauls were performed to assess the diel vertical migration behaviour of krill and to compare with previous findings (Werner and Buchholz 2013). At each filament station 20 animals were immediately deep-frozen after catch for further biochemical analyses (DNA/RNA ratios, elemental and biochemical composition) in the home

laboratories at AWI, Bremerhaven, Germany. Additionally, twenty animals were used to estimate moult activity and reproductive status of the females (SDS). Remaining animals were transferred to aerated plastic aquaria and maintained at in situ temperature (10°C). Approximately after 12 hours of incubation 8 animals in good condition were used for respiration measurements performed at 10°C using a closed-respirometry system with oxygen sensor spots and a 10-channel oxygen transmitter (PreSens, Germany). Respiration measurements were conducted for 3-6 h in the dark down to approx. 60% oxygen saturation using filtered seawater to

minimize bacterial oxygen consumption. Measurement of respiration rates involved the analysis of 500 µl water subsamples taken from the respiration chambers after each experiment which

Fig. 5.6.2 Habitus of ovigerous coastal krill, Nyctiphanes capensis. (Foto: C. Buchholz)

Fig. 5.6.1 The krill net comes up. The nine single nets have still to be heaved on deck. (Foto F. Buchholz)


were immediately deep-frozen in liquid nitrogen and stored at -80°C. At the home laboratory in Bremerhaven these subsamples will be analyzed for ammonia (NH4-N), the major form of dissolved nitrogen excreted by marine zooplankton. Specimens used for respiration measurements will be further used for stable isotope analyses to set up a stable isotope food-web of an upwelling filament structure.

Instantaneous growth rates (IGR) were determined in 24 animals each from stations outside, at the front and the centre of the filament. IGR were assessed to compare condition/wellbeing of krill. Therefore, 24 animals were placed individually in 1000 ml plastic beakers filled with seawater at in situ temperature and kept in the dark in a temperature controlled room. Three times a day animals were checked for moults and if so exuviae and corresponding animal were deep-frozen and stored at -80°C for later determination of the size increment at moult. Additionally, this experimental setup allowed estimation of the intermoult period (IMP) as an index of the trophic conditions in the field. All (remaining) samples were preserved in a buffered 4% formaldehyde-seawater solution for future taxonomical and biomass analyses.

5.7 NatMIRC Monthly Oceanographic Monitoring (MOM) and filament study (Richard Horaeb) The Benguela Upwelling system is characterized by high temporal and spatial variability in a short term and long term, with fluctuations in species composition and abundance. Zooplankton are useful indicators of climate change as they have short life spans and respond relatively quickly to changes in ocean conditions.

The National Marine Information and Research Centre (NatMIRC), has been conducting monitoring cruises along transects off Namibian coast for well over a decade – collecting physical, chemical and biological parameters. The 23°S transect has been the main monitoring line as it is an area of intense fishing and spawning grounds for sardine. Additional monitoring transects were added to the monitoring programme, namely 20, 25, 26 and 27°S. The WP-2 plankton net (200 µm mesh – vertical tow) is used to collect zooplankton from the upper 200 m of the water column or 10 m from the bottom in shallow stations. The samples are fixed and preserved in a borax buffered 4% formalin-seawater solution further analysis at home laboratory. The data from NatMIRC time series should be able to provide a retrospective view and close data gaps in current and future projects. The RV Meteor M100/1 cruise provided an opportunity to cover the routine monitoring on behalf of NatMIRC – an affirmation of long partnership between NatMIRC and German research institutes. All the nine monitoring stations along the 23 and 20°S lines were successfully sampled. Preliminary indications on the 23°S transect show the entire transect being dominated relatively by Calanoides and Metridia spp. Diatoms, mainly Coscinodiscus spp. dominated the inner shore stations.

Additional samples were taken during the filament study, notably inside the filament and outside the filament. Early observations show the inner filament station, though only sampled to 80m depth was rich with copepods, notably big specimens of Calanoides, Metridia and Centropages spp. as opposed to the outer filament station which yielded fewer and smaller size zooplankton, albeit sampled to 200m depth. The offshore outer filament stations were heavily dominated by diatoms (Coscinodiscus spp.).


Further samples were taken on the Kunene transect, Marine Phosphate Area. Several Multinet samples were also taken at deeper stations to capture deep living zooplankton. Further analysis for biomass, species distribution and abundance will be done at the home laboratory.

6 Ship’s Meteorological Station Weather information was supplied through the DWD sources to the scientific crew as processed and explained by Weather Technician Martin Stelzner, DWD. Basic weather data measured by the ship’s system were stored and are available on request (see also summary in 5.1.1, p 8).

7 Station List M100/1

Table 7.1 Table of CTD/LADCP/MSS stations and casts of M100/1 (The initial CTD marks the begin of other deployments at our near the same location)

Station No. M100/1-

Stat. Name (Depth)

Date Time [UTC]

Latitude Longitude CTD cast(s)

LADC Cast #

MSS casts

1861 1861 (39m)

Begin 01.09.2013 10:49 23° 00.06'S

14° 22.19'E

V0001F01 001 -

End 01.09.2013 13:52 23° 00.00'S

14° 22.19'E

1862

1862 (62m)

Begin 01.09.2013 11:58 22° 59.97'S 14° 19.83'E V0002F02 002 ‐

End 01.09.2013 12:44 22° 59.97'S 14° 19.83'E

1863

1863 (113m)

Begin 01.09.2013 13:37 22° 59.99'S 14° 13.81'E V0003F02 V0004F01

003 004

‐

End 01.09.2013 16:15 23° 00.38'S 14° 13.84'E

1864

1864 (130m)

Begin 01.09.2013 17:23 22° 59.99'S 14° 02.40'E V0005F02 005 ‐

End 01.09.2013 23:32 23° 02.84'S 14° 04.49'E

1865

1865 (140m)

Begin 02.09.2013 01:10 22° 59.99'S 13° 51.60'E V0006F01 006 ‐

End 02.09.2013 02:18 23° 00.00'S 13° 51.60'E

1866

1866 (147m)

Begin 02.09.2013 03:22 22° 59.99'S 13° 40.81'E V0007F01 007 ‐

End 02.09.2013 04:42 23° 00.00'S 13° 40.81'E

1867

1867 (222m)

Begin 02.09.2013 05:41 22° 59.99'S 13° 30.60'E V0008F01 V0008F02

008 ‐

End 02.09.2013 07:49 22° 59.99'S 13° 30.61'E

1868

1868 (348m)

Begin 02.09.2013 09:13 23° 00.00'S 13° 19.82'E V0009F01 009 ‐

End 02.09.2013 10:33 22° 59.98'S 13° 19.91'E

1869

1869 (312m)

Begin 02.09.2013 11:54 22° 59.99'S 13° 08.38'E V0010F01 V0010F03

010 ‐

End 02.09.2013 16:21 23° 03.16'S 13° 08.89'E

1870

X_1870 (131m)

Begin 03.09.2013 06:32 23° 00.03'S 14° 02.92'E V0011F01 011 ‐

End 03.09.2013 09:40 22° 59.86'S 14° 03.24'E

1871

1 (234m)

Begin 03.09.2013 12:49 22° 59.98'S 13° 29.99'E V0012F02 Scanfish

012 ‐

End 06.09.2013 05:52 17° 25.77'S 10° 35.05'E

1872

1872‐1 (1749m)

Begin 06.09.2013 19:47 19° 30.00'S 11° 40.00'E V0013F02 013 ‐

End 07.09.2013 14:35 20° 51.40'S 12° 23.14'E

1873

X_1873 (437m)

Begin 07.09.2013 14:51 20° 51.46'S 12° 23.19'E V0014F01 ‐ ‐

End 07.09.2013 15:25 20° 51.47'S 12° 23.20'E

1874

1874 (351m)

Begin 07.09.2013 20:34 20° 03.99'S 11° 58.00'E V0015F01 … V0015F05

014 ‐

End 08.09.2013 07:34 20° 08.64'S 11° 57.61'E

1875

1875 (321m)

Begin 08.09.2013 08:55 20° 18.23'S 12° 05.61'E ‐ ‐ ‐

End 08.09.2013 14:11 20° 32.40'S 12° 13.14'E

1876

1876 (318m)

Begin 08.09.2013 15:32 20° 21.01'S 12° 07.20'E V0016F02 V0016F04

015 ‐

End 09.09.2013 00:13 20° 19.85'S 12° 07.19'E


Station No. M100/1-

Stat. Name (Depth)

Date Time [UTC]


LADC Cast #

MSS casts

1877

1877 (415m)

Begin 09.09.2013 03:32 20° 48.06'S 12° 21.58'E V0017F01 …

016 017

001 …004 End 09.09.2013 18:02 20° 48.93'S 12° 21.70'E

1878

‐ (380m)

Begin 09.09.2013 18:49 20° 42.76'S 12° 18.83'E ‐ ‐ 005 …008 End 09.09.2013 19:43 20° 43.59'S 12° 18.83'E

1879

‐ (348m)

Begin 09.09.2013 20:33 20° 37.55'S 12° 16.00'E ‐ ‐ 009 …012 End 09.09.2013 21:27 20°38.33' S 12° 16.10'E

1880

‐ (326m)

Begin 09.09.2013 22:23 20° 32.35'S 12° 13.24'E ‐ ‐ 013 …016 End 09.09.2013 23:19 20° 33.74'S 12° 13.38'E

1881

‐ (316m)

Begin 10.09.2013 00:18 20° 27.15'S 12° 10.55'E ‐ ‐ 017 …020 End 10.09.2013 01:10 20° 28.30'S 12° 11.01'E

1882

‐ (317m)

Begin 10.09.2013 02:02 20° 22.01'S 12° 07.73'E ‐ ‐ 021 …024 End 10.09.2013 02:55 20° 22.92'S 12° 08.21'E

1883

‐ (323m)

Begin 10.09.2013 03:42 20° 16.76'S 12° 04.91'E ‐ ‐ 025 …028 End 10.09.2013 04:36 20° 17.47'S 12° 05.22'E

1884

‐ (334m)

Begin 10.09.2013 05:19 20° 11.53'S 12° 02.11'E ‐ ‐ 029 …032 End 10.09.2013 06:16 20° 12.15'S 12° 02.41'E

1885

‐ (346m)

Begin 10.09.2013 07:05 20° 06.39'S 11° 59.40'E ‐ ‐ 033 …036 End 10.09.2013 08:00 20° 07.29'S 11° 59.62'E

1886

‐ (355m)

Begin 10.09.2013 08:51 20° 01.15'S 11° 56.63'E ‐ ‐ 037 …040 End 10.09.2013 09:46 20° 02.01'S 11° 56.59'E

1887

‐ (362m)

Begin 10.09.2013 10:34 19° 55.98'S 11° 53.85'E ‐ ‐ 041 …044 End 10.09.2013 11:39 19° 57.14'S 11° 54.15'E

1888

‐ (371m)

Begin 10.09.2013 12:33 19° 50.83'S 11° 51.07'E ‐ ‐ 045 …048 End 10.09.2013 13:30 19° 51.73'S 11° 51.52'E

1889

‐ (373m)

Begin 10.09.2013 14:17 19° 45.60'S 11° 48.29'E ‐ ‐ 049 …052 End 10.09.2013 15:20 19° 46.49'S 11° 48.53'E

1890

‐ (366m)

Begin 10.09.2013 16:05 19° 40.36'S 11° 45.50'E ‐ ‐ 053 …056 End 10.09.2013 16:59 19° 41.18'S 11° 45.80'E

1891

‐ (361)

Begin 10.09.2013 17:44 19° 35.19'S 11° 42.72'E ‐ ‐ 057 …060 End 10.09.2013 18:40 19° 36.03'S 11° 42.89'E

1892

1872‐1 (368)

Begin 10.09.2013 19:31 19° 29.97'S 11° 40.00'E V0018F02 018 061 …064 End 10.09.2013 21:36 19° 30.00'S 11° 39.98'E

1893

1893 (370m)

Begin 11.09.2013 00:48 19° 51.98'S 11° 51.70'E ‐ ‐ ‐

End 11.09.2013 04:46 20° 00.08'S 11° 55.90'E

1894

X_1894 (362m)

Begin 11.09.2013 05:21 19° 56.13'S 11° 53.90'E V0019F01 019 ‐

End 11.09.2013 11:29 19° 56.11'S 11° 53.93'E

1895

1872‐1 (368m)

Begin 11.09.2013 14:31 19° 30.14'S 11° 40.26'E V0020F02 020 ‐

End 12.09.2013 00:25 19° 29.98'S 11° 40.22'E

1896

1896 (966m)

Begin 12.09.2013 03:29 19° 29.99'S 11° 09.60'E V0021F01 021 ‐

End 12.09.2013 07:10 19° 42.41'S 11° 16.11'E

1897 1897 (1062m)

Begin 13.09.2013 01:02 20° 59.98'S 11° 56.99'E V0022F02 022 ‐

End 13.09.2013 01:46 20° 59.98'S 11° 56.99'E

1898

1898 (1042m)

Begin 13.09.2013 04:28 20° 36.01'S 11° 44.29'E V0023F01 V0023F02

023 ‐

End 13.09.2013 12:30 20° 36.00'S 11° 44.27'E

1899

1899 (1015m)

Begin 13.09.2013 13:44 20° 30.17'S 11° 41.09'E ‐ ‐ ‐

End 13.09.2013 16:36 20° 37.04'S 11° 44.73'E

1900

1900 (1042m)

Begin 13.09.2013 16:56 20° 36.00'S 11° 44.30'E ‐ ‐ ‐

End 13.09.2013 21:12 20° 40.82'S 11° 46.63'E

1901

1901 (733m)

Begin 14.09.2013 00:03 20° 54.28'S 12° 09.15'E ‐ ‐ ‐

End 14.09.2013 16:10 19° 39.11'S 11° 29.59'E

1902

1902 (565m)

Begin 14.09.2013 16:28 19° 39.99'S 11° 29.99'E V0024F02 024 ‐

End 14.09.2013 16:59 19° 39.99'S 11° 30.00'E

1903 WW200 Begin 14.09.2013 20:08 20° 00.00'S 11° 47.40'E V0025F01 025 ‐


Station No. M100/1-

Stat. Name (Depth)

Date Time [UTC]


LADC Cast #

MSS casts

70 (436m)

End 14.09.2013 22:59 20° 00.00'S 11° 47.40'E

1904

WW20060 (344m)

Begin 15.09.2013 00:23 19° 59.98'S 11° 58.18'E V0026F01 026 ‐

End 15.09.2013 01:36 19° 59.98'S 11° 58.18'E

1905

WW20050 (278m)

Begin 15.09.2013 02:47 20° 00.01'S 12° 08.99'E V0027F01 027 ‐

End 15.09.2013 03:48 20° 00.00'S 12° 09.00'E

1906

WW20040 (212m)

Begin 15.09.2013 05:02 20° 00.01'S 12° 19.79'E V0028F01 V0028F03

028 029

‐

End 15.09.2013 12:27 19° 59.98'S 12° 19.78'E

1907

WW20030 (149m)

Begin 15.09.2013 13:45 19° 59.98'S 12° 29.99'E V0029F01 030 ‐

End 15.09.2013 14:42 19° 59.98'S 12° 29.99'E

1908

WW20020 (123m)

Begin 15.09.2013 15:56 20° 00.00'S 12° 40.77'E V0030F02 031 ‐

End 15.09.2013 16:37 20° 00.00'S 12° 40.78'E

1909

WW20010 (97m)

Begin 17.09.2013 11:15 19° 59.98'S 12° 51.58'E V0031F02 032 ‐

End 17.09.2013 13:31 20° 02.81'S 12° 51.81'E

1910

WW20005 (59m)

Begin 17.09.2013 14:14 19° 59.97'S 12° 56.39'E V0032F01 ‐ ‐

End 17.09.2013 14:34 19° 59.97'S 12° 56.39'E

1911 WW20002 (28m)

Begin 17.09.2013 15:07 19° 59.99'S 12° 59.98'E V0033F01 ‐ ‐

End 17.09.2013 15:22 19° 59.92'S 12° 59.99'E

1912

1912 (117m)

Begin 18.09.2013 03:43 17° 59.99'S 11° 40.76'E V0034F01 033 ‐

End 18.09.2013 09:35 18° 02.23'S 11° 40.89'E

1913

1913 (53m)

Begin 18.09.2013 13:40 17° 17.98'S 11° 42.01'E V0035F02 ‐ ‐

End 18.09.2013 14:45 17° 18.52'S 11° 42.00'E

1914

1914 (148m)

Begin 18.09.2013 15:57 17° 18.00'S 11° 30.00'E V0036F01 V0036F02

034 ‐

End 18.09.2013 21:34 17° 17.99'S 11° 30.00'E

1915

1915 (401m)

Begin 18.09.2013 22:54 17° 18.15'S 11° 18.59'E V0037F01 035 ‐

End 19.09.2013 12:08 17° 19.76'S 11° 20.86'E

1916

1916 (833m)

Begin 19.09.2013 13:20 17° 17.99'S 11° 11.97'E V0038F02

036 ‐

End 19.09.2013 16:12 17° 20.27'S 11° 12.03'E

1917

1917 (180m)

Begin 22.09.2013 06:26 24° 15.99'S 14° 03.02'E V0039F02 037 ‐

End 22.09.2013 08:19 24° 15.99'S 14° 03.02'E

1918

1918 (204m)

Begin 22.09.2013 08:59 24° 15.99'S 13° 59.98'E V0040F01 038 ‐

End 22.09.2013 10:37 24° 15.99'S 13° 59.98'E

1919

1919 (301m)

Begin 22.09.2013 12:28 24° 15.96'S 13° 42.02'E V0041F02 039 ‐

End 22.09.2013 14:03 24° 15.96'S 13° 42.02'E

1920

1920 (142m)

Begin 22.09.2013 21:05 22° 59.99'S 13° 44.99'E V0042F02 040 ‐

End 23.09.2013 01:33 22° 59.98'S 13° 45.00'E

1921

WW23020 (132m)

Begin 23.09.2013 03:17 23° 00.00'S 14° 02.40'E V0043F01 041 ‐

End 23.09.2013 12:27 23° 01.92'S 14° 02.63'E

1922

1922 (628m)

Begin 23.09.2013 17:19 22° 59.99'S 13° 08.40'E V0044F02 042 ‐

End 23.09.2013 21:06 23° 03.48'S 13° 02.57'E

1923

1923 (358m)

Begin 23.09.2013 22:49 22° 59.99'S 13° 17.98'E V0045F01 043 ‐

End 24.09.2013 04:27 23° 00.00'S 13° 18.01'E

1924

1924 (896m)

Begin 24.09.2013 07:18 22° 59.99'S 12° 48.00'E V0046F01 V0046F03

044 045

‐

End 24.09.2013 23:05 23° 04.80'S 12° 47.29'E

1925 1925 Begin 25.09.2013 04:34 22° 59.99'S 11° 48.00'E V0047F01 046 ‐


Station No. M100/1-

Stat. Name (Depth)

Date Time [UTC]


LADC Cast #

MSS casts

(2909m) End 25.09.2013 16:30 23° 08.81'S 11° 48.04'E V0047F02 047

1926

1926 (386m)

Begin 26.09.2013 03:34 21° 19.53'S 12° 36.74'E ‐ ‐ ‐

End 27.09.2013 06:31 19° 05.49'S 11° 25.77'E

1927

1927 (493m)

Begin 27.09.2013 07:18 19° 05.13'S 11° 24.36'E ‐ ‐ ‐

End 27.09.2013 07:26 19° 05.13'S 11° 24.36'E

1928

1928 (846m)

Begin 27.09.2013 08:50 18° 59.99'S 11° 12.01'E V0048F01 048 ‐

End 27.09.2013 11:33 18° 59.99'S 11° 12.03'E

1929

1929 (1283m)

Begin 27.09.2013 12:52 18° 59.98'S 10° 59.99'E V0049F01 049 ‐

End 27.09.2013 15:54 18° 59.98'S 10° 59.98'E

1930

1930 (1822m)

Begin 27.09.2013 18:11 18° 59.99‘S 10° 36.60'E V0050F02 050 ‐

End 27.09.2013 23:12 18° 59.98'S 10° 36.52'E

1931

1931 (367m)

Begin 28.09.2013 08:19 19° 35.99'S 11° 42.00'E V0051F01 051 ‐

End 28.09.2013 12:19 19° 39.74'S 11° 44.31'E

1932

1932 (379m)

Begin 28.09.2013 14:06 19° 49.14'S 11° 48.86'E V0052F01 ‐ ‐

End 28.09.2013 19:43 19° 59.76'S 11° 55.61'E

1933

1933 (353m)

Begin 28.09.2013 20:26 19° 55.72'S 11° 55.59'E ‐ ‐ 065 ..075 End 28.09.2013 22:33 20° 00.59'S 11° 57.58'E

1934

1934 (333m)

Begin 29.09.2013 02:50 20° 27.02'S 12° 08.88'E V0053F01 052 ‐

End 29.09.2013 04:57 20° 28.30'S 12° 09.21'E

1935

1935 (434m)

Begin 29.09.2013 11:31 21° 11.98'S 12° 32.99'E V0054F01 053 ‐

End 29.09.2013 15:40 21° 17.59'S 12° 32.10'E

8 Data and Sample Storage and Availability All data and samples collected during cruise M100/1 refer to the GENUS program. All data will be made available by the end of 2014. In a first stage the GENUS project stores all data of the cruise on an ftp-server at the Leibniz-Institute for Baltic Research in Warnemünde. The server can be accessed through ftp://ftp.iowarnemuende.de. The scientist in charge and to contact for access is Dr. Anja Eggert ([email protected]). During the first stage most data are only available to the user groups of the GENUS program and to affiliated project partners.

However, one central task of the GENUS program is the binding agreement to share the collected data with the scientific community. Therefore, GENUS has established a cooperation with the Pangaea Database (www.pangaea.de). This means that all data collected during this cruise as well as for all other GENUS cruises will be transferred and finally stored in the Pangaea Database by the end of the year 2014 and then accessible according to the release requirements of the respective working groups.

All biological and biogeochemical samples collected during this cruise were sent under frozen conditions (-80°C or -20°C) to the respective home laboratories in Germany (IOW, IHF, ZMT, MarZoo, AWI). The majority of the samples will be used for measurements and experimentswithin the GENUS program. The remaining samples are submitted to the German archives according to the agreement with the Deutsche Zentrum für Marine Biodiversitätsforschung (DZMB).


9 Acknowledgements The support of captain, officers and crew was extraordinary. This also applies to the on-shore support in solving problems.

The cruise was characterized by a “we are in one boat” attitude towards fulfilling our science objectives within an international frame. We congratulate to the whole crew’s performance and are looking forward to again sail on FS METEOR on M103.

We would also like to express our gratitude to the Leitstelle METEOR for its valuable support. Ship time was provided by the Deutsche Forschungsgemeinschaft and was supported by the GENUS program of the Federal Ministry of Education and Research (FKZ: 03F0497A).

Fig. 9.1 Outstanding event was the celebration of the one hundredths cruise of the RV METEOR, M100/1, being

initiated by Three Cheers in the bar: we are proud of our able and handsome ship and consider it a great privilege to be allowed to use such a perfect ”living instrument” for our research, solidly founded on the experience and unlimited support of the ship’s command and crew: we were a perfect team! Thank you all very much for your continuing support!

Foto: D. Peterke

10 References

Al-Mutairi, H., Landry, M.R., 2001. Active export of carbon and nitrogen at Station ALOHA by diel migrant zooplankton. Deep-Sea Research Part II-Topical Studies in Oceanography 48 (8-9), 2083-2103

Bakun, A. (1990) Global climate change and intensification of coastal ocean upwelling. Science 247: 198-201

Buchholz, F. (2003) Experiments on the physiology of Southern and Northern krill, Euphausia superba and Meganyctiphanes norvegica, with emphasis on moult and growth - a review. Mar. Freshwater Behav. Physiol. 36: 229-247

Christiansen, B., Drüke, B., Koppelmann, R., Weikert, H., 1999. The bear-bottom zooplankton at the abyssal BIOTRANS site, northeast Atlantic: composition, abundance and variability. Journal of Plankton Research 21, 1847-1863


Dam, H.G., Roman, M.R., Youngbluth, M.J., 1995. Downward export of respiratory carbon and dissolved inorganic nitrogen by diel-migrant mesozooplankton at the JGOFS Bermuda time-series station. Deep-Sea Research Part I-Oceanographic Research Papers 42 (7), 1187-1197.

Dickson, A.G., Sabine, C.L., Christian, J.R., 2007. Guide to the best practices for ocean CO2 measurements. UNESCO

Huang, J., Golombek, A., Prinn, R., Weiss, R., Fraser, P., Simmonds, P., Dlugokencky, E.J., Hall, B., Elkins, J., Steele, P., Langenfelds, R., Krummel, P. Dutton, G., and Porter, L. 2008. Estimation of regional emissions of nitrous oxide from 1997 to 2005 using multinetwork measurements, a chemical transport model, and an inverse method. Journal of Geophysical Research 113, doi:10.1029/2007JD009381

Huenerlage, K. and Buchholz, F. 2013 Krill of the northern Benguela Current and the Angola-Benguela frontal zone compared: physiological performance and short-term starvation in Euphausia hanseni. Journal of Plankton Research 35 (2),337-351

Köster, M., Krause, C., Paffenhöfer, G.A., 2008. Time-series measurements of oxygen consumption of copepod nauplii. Marine Ecology-Progress Series 353, 157-164

Landry, M., Hassett, R.P., 1982. Estimating the grazing impact of marine microzooplankton. Marine Biology 67, 283-288

Loick, N., Ekau, W., Verheye, H.M., 2005. Water-body preferences of dominant calanoid copepod species in the Angola-Benguela frontal zone. African Journal of Marine Science 27 (3), 597-608

Lutjeharms, J. R. E., Shillington, F.A., Duncombe Rae, C.M. (1991) Observations of extreme upwelling filaments in the southeast Atlantic Ocean. Science 253, 774-776

Machida, T., Nakazawa, T., Fuji, Y., Aoki, S., and Watanabe, O., 1995. Increase in the atmospheric nitrous oxide concentration during the last 250 years. Geophysical Research Letters 22, 2921-2924McElroy, M.B., 1983. Marine biological controls on atmospheric CO2 and climate. Nature 302, 328-329

Mintrop, L., 2005. The Versatile Instrument for the Determination of Titration Alkalinity: Manual for version 3s and 3c, Marianda

Robinson, C., Steinberg, D.K., Anderson, T.R., Aristegui, J., Carlson, C.A., Frost, J.R., Ghiglione, J.-F., Hernandez-Leon, S., Jackson, G.A., Koppelmann, R., Queguiner, B., Ragueneau, O., Rassoulzadegan, F., Robison, B.H., Tamburine, C., Tanaka, T., Wishner, K.F., Zhang, J., 2010. Mesopelagic zone ecology and biogeochemistry - a synthesis. Deep-Sea Research II 57, 1504-1518

Sierburth, J.M., Smetacek, V., Lenz, J., 1978. Pelagic ecosystem structure: Heterotrophic compartments of the plankton and their relationsship to plankton size fractions. Limnology and Oceanography 23, 1256-1263

Steinberg, D.K., Cope, J.S., Wilson, S.E., Kobari, T., 2008. A comparison of mesopelagic mesozooplankton community structure in the subtropical and subarctic North Pacific Ocean. Deep-Sea Research Part II-Topical Studies in Oceanography 55 (14-15), 1615-1635

Verheye, H.M., Hagen, W., Auel, H., Ekau, W., Loick, N., Rheenen, I., Wencke, P., Jones, S., 2005. Life strategies, energetics and growth characteristics of Calanoides carinatus (Copepoda) in the Angola-Benguela frontal region. African Journal of Marine Science 27 (3), 641-651

Werner, T. and Buchholz, F. 2013. Diel vertical migration behaviour in Euphausiids of the northern Benguela current: seasonal adaptations to food availability and strong gradients of temperature and oxygen. J. Plankton Res. 35(4), 792-812


Wiebe, P.H., Morton, A.W., Bradley, A.M., Backus, R.H., Craddock, J.E., Barber, V., Cowles, T.J., Flierl, G.R., 1985. New developments in the MOCNESS, an apparatus for sampling zooplankton and micronekton. Marine Biology 87, 313-323

Documents

Physics, Biogeochemistry and Ecology of Upwelling ...genus.zmaw.de/fileadmin/user_upload/genus/template/Meteor_100_1... · c/o MARUM – Zentrum für ... (MOM) and filament study