Frontiers in Marine Science (Jun 2019)
Microzooplankton Distribution and Dynamics in the Eastern Fram Strait and the Arctic Ocean in May and August 2014
Abstract
Microzooplankton community structure, distribution, growth, and herbivory were examined in the eastern Fram Strait and Arctic Ocean shelf affected by the Atlantic water inflow in May (during the spring bloom) and August (post-bloom, summer stratification) 2014. In May, integrated microzooplankton biomass in the upper 100 m ranged from 0.16 g C m-2 above the slope to 2.3 g C m-2 within the West Spitsbergen Current (0.71 g C m-2 on average), where it peaked in the mixed layer at 206 μg C L-1. This is the highest volumetric microzooplankton biomass recorded so far in the Arctic. It primarily consisted of mixotrophic oligotrich ciliates from the genus Strombidium, which were dominant in the spring and formed a surface bloom (79 × 103 cells L-1). The heterotrophic dinoflagellates Gyrodinium and Protoperidinium were abundant at the diatom-dominated stations in the ice-covered waters during both seasons. In the summer, a more diverse community included a large proportion of heterotrophic and mixotrophic dinoflagellates, tintinnids, and other ciliates. Microzooplankton biomass increased to the average of 1.27 g C m-2. At the ice-covered and open water stations in the Yermak shelf and deep basin, microzooplankton grew at 0.04 to 0.38 d-1; their species-specific growth rates were up to 1.79 d-1. Microzooplankton herbivory on average removed 72% (in two experiments > 100%) of daily primary production with the exception of samples dominated by Phaeocystis pouchetii colonies. The results indicate that microzooplankton play a significant role in the carbon cycle in this Atlantic-influenced polar system.
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