Enzyme activities of digestive and metabolic enzymes of Calanus finmarchicus from Maria S. Merian cruise MSM26 in spring 2013

The present study aimed to contribute to the knowledge on the intraspecific variations of enzyme activities in populations of Calanus finmarchicus from different longitudes across the North Atlantic Ocean and their relation to changing environmental conditions. C. finmarchicus was sampled across the North Atlantic in basins with decreasing temperature regimes from east to west (Iceland Basin, Irminger Basin and Labrador Basin) in late March/early April 2013. Potential maximum enzyme activities of digestive (proteinases and lipases/esterases) and metabolic (citrate synthase) enzymes of copepods from all sampling stations were analysed and thermal profiles (5-50°C) of enzyme activities were determined. In order to investigate its acclimation potential, C. finmarchicus were acclimated to 4°C and 15°C for two weeks and thermal profiles of enzyme activities were compared afterwards.

Abundance of Cnidaria and Ctenophora taxa in the North Atlantic sampled during the G. O. Sars Cruise in May 2013

In recent years a global increase in jellyfish (i.e. Cnidarians and Ctenophores) abundance and a rise in the recurrence of jellyfish outbreak events have been largely debated, but a general consensus on this matter has not been achieved yet. Within this debate, it has been generally recognized that there is a lack of reliable data that could be analyzed and compared to clarify whether indeed jellyfish are increasing throughout the world ocean as a consequence of anthropogenic impact and hydroclimatic variability. During the G.O. Sars cruise jellyfish were collected at different depths in the 0-1000m layer using a standard 1 m**2 Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) (quantitative data), Harstad and macroplankton trawls (qualitative data). The comparison of records collected with different nets during the G.O. Sars transatlantic cruise shows that different sampling gears might provide very different information on jellyfish diversity. Indeed, the big trawls mostly collect relatively large scyphozoan and hydrozoan species such as Atolla, Pelagia, Praya, Vogtia, while small hydrozoans (e.g. Clytia, Gilia, Muggiaea) and early stages of ctenophora are only caught by the smaller nets.

Zooplankton abundance and size structure in the North Atlantic from MSM26_127-13

Data on zooplankton abundance and biovolume were collected in concert with data on the biophysical environment at 9 stations in the North Atlantic, from the Iceland Basin in the East to the Labrador Sea in the West. The data were sampled along vertical profiles by a Laser Optical Plankton Counter (LOPC, Rolls Royce Canada Ltd.) that was mounted on a carousel water sampler together with a Conductivity-Temperature-Depth sensor (CTD, SBE19plusV2, Seabird Electronics, Inc., USA) and a fluorescence sensor (F, ECO Puck chlorophyll a fluorometer, WET Labs Inc., USA). Based on the LOPC data, abundance (individuals/m**3) and biovolume (mm3/m**3) were calculated as described in the LOPC Software Operation Manual [(Anonymous, 2006), http://www.brooke-ocean.com/index.html]. LOPC data were regrouped into 49 size groups of equal log10(body volume) increments, see Edvardsen et al. (2002, doi:10.3354/meps227205). LOPC data quality was checked as described in Basedow et al. (2013, doi:10.1016/j.pocean.2012.10.005). Fluorescence was roughly converted into chlorophyll based on filtered chlorophyll values obtained from station 10 in the Labrador Sea. Due to the low number of filtered samples that was used for the conversion the resulting chlorophyll values should be considered with care. CTD data were screened for erroneous (out of range) values and then averaged to the same frequency as the LOPC data (2 Hz). All data were processed using especially developed scripts in the python programming language. The LOPC is an optical instrument designed to count and measure particles (0.1 to 30 mm equivalent spherical diameter) in the water column, see Herman et al., (2004, doi:10.1093/plankt/fbh095). The size of particles as equivalent spherical diameter (ESD) was computed as described in the manual (Anonymous, 2006), and in more detail in Checkley et al. (2008, doi:10.4319/lo.2008.53.5_part_2.2123) and Gaardsted et al. (2010, doi:10.1111/j.1365-2419.2010.00558.x).

Ex situ respiration rates measured in water column samples during the James Cook cruise JC087 in June 2013

Oxygen concentration and rate of change of oxygen were measured using the Unisense Oxygen Microsensor System. Water from different depth was taken from CTD attached niskin bottle. Measurements were conducted in 2 ml vials provided by Unisense and lasted for a minimum of two minutes after a stable rate was achieved. The sampling interval was 6 seconds. Transport containers, tubes and vials for measurements were covered with light proof black foil for dark-measurements.

Vertical distribution and abundance of small zooplankton from the James Cook cruise JC087

Zooplankton samples were collected daily at the PAP site, using a Multinet of the type Midi with 50 µm nets. 5 depth strata (1000-500, 500-300, 300-100, 100-50 and 50-0 m) were collected at each sampling. The samples were preserved in 2% borax bufferred formalin. Zooplankton were identified on a species / genus level including different life-stages and eggs; at least 400 individuals were counted for each sample. When present, 10 individuals of each species and life-stages (for copepods) were measured for their prosome or total length.

Mesozooplankton abundance data from Disko Bay, West Greenland, 2008

The study site was located in the Disko Bay off Qeqertarsuaq, western Greenland. Due to land-connected sea ice coverage during winter, 2 sampling sites were combined. At the first site in winter (21 February to 23 March 2008), sampling was conducted through a hole in the ice at ca. 65 to 160 m depth approximately 0.5 nautical mile (n mile) south of Qeqertarsuaq (69° 14' N, 53° 29' W). In spring and summer (9 April to 18 July), sampling was done at a monitoring station 1 n mile south from Qeqertarsuaq (69° 14' N, 53° 23' W) at 300 m depth. Sampling was carried out between 10:00 and 17:00 h. During sampling from the ice, mesozooplankton was collected using a modified WP-2 net (45 µm) equipped with a closing mechanism (Hydrobios). Samples were collected in 3 depth strata (0-50, 50-100, and 100-150 m). During ship-based sampling, mesozooplankton was collected with a multinet (50 µm) equipped with a flow meter (Multinet, Hydrobios type midi), and 2 additional depth strata (150-200m and 200-250 m) were included. In addition to the seasonal study one diurnal investigation with sampling every 6 h was conducted from 29 April at 12:00 h to 30 April 30 at 12:00 h. Samples were immediately preserved in buffered formalin (5% final concentration) for later analyses. Biomass values of the different copepod species were calculated based on measurements of prosome length, and length/weight relationships. Two regressions for Calanus spp. were established for biomass calculations: one applicable prior to and during the phytoplankton bloom until 4 May, and another from 9 May onwards.