Map 16 Issued from : M. Bode, R. Koppelmann, L. Teuber, W. Hagen & H. Auel inGlobal Biogeochemical Cycles, 2018, 32. [p.846, Fig.2).
Station map during ANT-XXIX/1 of RV Polarstern Expedition in October/November 2012, in the Eastern Atlantic Ocean (between 24°N and 21°S).
Nota: << Detailed hydrographic data sets down to 200 and 2000 m (Bode & al., 2015; 2018) and Chla distributions (Bode & al., 2015).Station 5 (23°7N) was located in the subtropical North Atlantic (STNA) with high sea surface salinity (SSS) of 36.6 and high sea surface temperature (SST) of 25°C. According to the fluorescence signal, Chla concentration was low, and the primary production was lowest (445 mg C m-2 day-1) compared to the other stations. Stations 8, 9 and 10 (15°N-2°N) were situated in the tropical North Atlantic (TNA). These stations were characterized by the highest SST ranging from 27°C at station 10 to 29°C at station 9 and relatively low SSS of 35.6 (stn.8 and 10) and 35.0 (stn.9). The primary production was relatively high with 650 mg C m-2 day-1 at station 8, 563 mg C m-2 day-1 at station 9, and 907 mg C m-2 day-1 at station 10; Station 14 (14°S) was located in the subtropical South Atlantic (STSA) in direct vicinity ofd the Angola Gyre with lower SST (21°C) but higher SSS of 36.5 compared to the TNA. The intermediate Chla maximum was located between 50 and 100 m, while the primary production was moderately high with 665 mg m-2 day-1. Station 17 (21°S) was situated in the Benguela Current influenced region (BCIR) and characterized by relatively low SST (18°.5°C) and low SSS (35.6) There was only weak stratification by temperature or salinity down 150 m depth. Chla concentration were highest in this region, as was the primary production with 930 mg C m-2 day-1.
Total copepod community (with a Hydrobios Multinet, mesh aperture 150 µm) consumption integrated over the entire 0-2000 m water column varied from 202 mg C m-2 day-1 at station 14 to 604 mg C m-2 day-1 at station 8, potentially ingesting 30-93% of the carbon produced by the primary production.
Highest ingestion rates of calanoid communities integrated from 0-2000 m were found in the TNA (323-541 mg C m-2 day-1, 45-83% of the primary production), consumption was intermediate in the BCIR (301 mg C m-2 day-1, 32% of the primary production) and lowest in the STNA (266 mg C m-2 day-1, 60% of the primary production) and STSA (151 mg C m-2, 23% of the primary production).
The total net loss of particulate organic carbon (POC) by copepods, defined as gross consumption minus fecal pellet egestion integrated from 0 to 2000, varied from 142 mg C m-2 day-1 in the STSA to 423 mg C m-2 day-1 in the TNA.
The relative impact of net copepod ingestion (= consumption - egestion) on the primary production (PP) was highest in the TNA (37-65% PP) and in the STNA (50% PP) and lowest in the BCIR (28% PP). Of these, 16-58% of PP could be attributed to calanoid copepods and 5-9% of PP to cyclopoids .
A total of 28 calanoid copepods species were studied: DM-specific (calculated from median total length) respiration rates ranged from 0.3 µl O2 mg DM-1 hr-1 for deep-dwelling females of Rhincalanus cornutus and CV of Gaetanus brevicornis and Pareucalanus spp. to 16 µl O2 mgDM-1 hr-1 for epipelagic Undinula vulgaris. Large differences in adjusted metabolic rates (AMRs; 15°C and 0.7 mg DM) were determined between species. All eucalanid species, diapausing CV of Calanoides natalis, and females of Paraeuchaeta aequatorialis and Metridia princeps had lowest mean AMRs between 0.5 and 0.8 µl O2 mg DM-1 hr-1.
Typical mesopelagic species such as Scottocalanus securifrons, Chirundina stretsii, Euchirella pulchra, E. splendens, E. curticauda, Gaetanus pileatus, G. kruppii, Megacalanus princeps showed generally low AMRs of 1-2 µl O2 mgDM-1 hr-1.
Highest mean AMRs of > 4 µl O2 mg DM-1 hr-1 were measurd for epipelagic Undinula vulgaris, Candacia pachydactyla, C. ethiopica, Euchaeta marina.
Only males of C. ethiopica and U. vulgaris showed significantly lower respiration rates than females.
Epipelagic Euchirella splendens and Euchaeta marina exhibited significantly higher AMRs than specimens collected at mesopelagic depths.
Individual in situ oxygen consuoption rates were converted to carbon units approximating minimum food requirements and thus potential ingestion for each species and community.
Individual carbon demands were 0.7 and 0.9 µg C ind-1 day-1 for CV and females of Rhincalanus cornutus, respectively and 1.1 mg C ind-1 day-1 for diapausing CV of Calanoides natalis.
Highest carbon fdemands of > 20 µg C ind-1 day-1 were measured in the upper 100 m for Euchirella splendens, Undinula vulgaris, Candacia pachydactyla, Euchaeta marina, Pleuromamma xiphias, Neocalanus robustior. Euchirella splendens collected in the upper 100 m showed a maximum mean daily ingestion rate of 115 µg ind-1 day-1, while females of Undinella vulgaris, Candacia pachydactyla, Euchaeta marina from the epipelagic zone ingested on average 70-75 µg C ind-1 day-1.
Minimum daily ingestion rates of < 10 µg C ind-1 day-1 were determined for deep-dwelling females of Euchirella pulchra, Candacia curticauda, Eucalanus hyalinus, Rhincalanus nasutus, Pareucalanus spp., and copepodids of Gaetanus pileatus, G. brevicornis, with minima of 1.7 and 2.3 µg C ind-1 day-1 for CV and females, respectively, of Rhincalanus cornutus. >>