Grazing rate of microzooplankton measured experimentally in the North Atlantic during the Maria S. Merian cruise MSM26, spring 2013

• Main Authors: Hänselmann, Kristin, Walter, Bettina
• Format: Dataset
• Language: English
• Published: PANGAEA 2013
• Subjects: Basin Scale Analysis; Synthesis and Integration; Chlorophyll a; Copepoda; CTD/Rosette; CTD-RO; Date/Time of event; DEPTH; water; Dilution; Duration; Elevation of event; EURO-BASIN; Event label; Experiment; Growth rate; Latitude of event; Light intensity; Longitude of event; Maria S. Merian; MSM26; MSM26_126-1; MSM26_127-4; MSM26_131-18; MSM26_133-12; MSM26_134-4; MSM26_135-14; MSM26_136-11; MSM26_137-9; North Atlantic Ocean; Temperature; Calanus finmarchicus; North Atlantic; Copepods
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.819256; https://doi.org/10.1594/PANGAEA.819256

The microzooplankton grazing dilution experiments were conducted at stations 126, 127, 131 and 133-137, following Landry & Hassett (1982). Seawater samples (whole seawater – WSW) were taken via Niskin bottles mounted on to a CTD Rosette out of the chlorophyll maximum at each station. Four different dilution levels were prepared with WSW and GF/F filtered seawater – 100% WSW, 75% WSW, 50% WSW and 25% WSW. The diluted WSW was filled in 2.4 L polycarbonate bottles (two replicates for every dilution level). Three subsamples (250 - 500 mL depending on in situ chlorophyll) of the 100% WSW were filtered on to GF/F filters (25 mm diameter) and chlorophyll was extracted in 5 mL 96% ethanol for 12-24 hours. Afterwards it was measured fluorometrically before and after the addition of HCl with a Turner fluorometer according to Jespersen and Christoffersen (1987) on board of the ship. In addition, one 250 mL subsample of the 100% WSW was fixed in 2% Lugol (final concentration), to determine the microzooplankton community when back at the Institute for Hydrobiology and Fisheries Science in Hamburg. Also, one 50 mL subsample of the 100% WSW was fixed in 1 mL glutaraldehyde, to quantify bacteria abundance. The 2.4 L bottles were put in black mesh-bags, which reduced incoming radiation to approximately 50% (to minimize chlorophyll bleaching). The bottles were incubated for 24 hours in a tank on deck with flow-through water, to maintain in situ temperature. An additional experiment was carried out to test the effect of temperature on microzooplankton grazing in darkness. Therefore, 100% WSW was incubated in the deck tank and in two temperature control rooms of 5 and 15°C in darkness (two bottles each). The same was done with bottles where copepods were added (five copepods of Calanus finmarchicus in each bottle; males and females were randomly picked and divided onto the bottles). In addition, two 100% WSW bottles with five copepods each were incubated at in situ temperature at 100% light level (without mesh-bags). All ...