Once on deck, the net was rinsed with seawater and the samples
were maintained at 4 °C while awaiting the processing. First, we split
the samples by the beaker technique (Van Guelpen et al., 1982). One
half was fractionated for the 100–200, 200–500, 500–1000 and
N1000 μmsize classes, and immediately frozen in liquid nitrogen before
being stored in the freezer (−80 °C) for subsequent enzymatic analyses.
The other was split into two new subsamples: one was frozen at
−20 °C for biomass and isotopic determinations; the other was stored
in plastic bottles filled with buffered formaldehyde (4% final concentration)
for taxonomic analysis. Size fractionation was made in both cases
as well. Organisms over 5000 μm such as jellyfish were not included in
our calculations. However, they were counted and the diameter of the
umbrella was measured with a calibrated rule in order to convert
them into dry mass (DM) using the equation DM = 0.03 Diameter2.3
given in Møller and Riisgård (2007) for the genus Aquarea.