Biology and the Carbon Cycle
Mesozooplankton Community Structure
in the Arctic Ocean in Summer
Delphine Thibault
Ocean organisms range in size from tiny bacteria (0.11 m) to whales
(over 30 m). Mesozooplankton (2002000 m) represent a link between
smaller organisms (< 200 m), such as phytoplankton and microzooplank-
ton (on which they graze) and larger grazers (> 200 m), such as macro-
zooplankton and fish (which feed on them). By knowing their biomass,
composition and metabolism, we can estimate the role of mesozooplank-
ton in the pelagic food web and the carbon cycle.
During AOS-94, as part of the biological study, the biomass, the specific
composition and the chemical composition of mesozooplankton were esti-
mated in the upper 500 m of the Arctic Basin. Where possible, three layers
were sampled at each station (0100, 100200 and 200500 m). Also, the
content of the gut pigments, as an
indicator of grazing, was directly
measured on the main species and
stages in the upper layer.
The mesozooplankton biomass
in the first 100 m increased quadrat-
showing a maximum around 87N.
A high mesozooplankton biomass
(1942 mg dry weight/m3) was ob-
served in the upper two layers (0
200 m), while in the deepest layer
(200500 m) the biomass was much
lower, ranging from 4 to 16 mg DW/m3. The integrated mesozooplankton
The plankton net
being lowered for
standing stock varied between 0.4 and 10 g DW/m2 and appear to be signif-
sampling on the
icantly higher than previously reported for the Arctic Ocean (Conover and
Polar Sea.
Huntley 1991).
The mesozooplankton carbon content was nearly constant over the
whole study area (around 40% of the dry weight), although it appears to
be lower at the ice edge stations. Those variations might be related to modi-
fications in the zooplanktonic population. The C/N (g/g) ratio for the
Delphine Thibault is from the Dpartment d'ocanographie of the Universite du Qubec Rimouski, Quebec,
Canada.
37
Previous Page
