Distribution and abundance of choanoflagellates (Acanthoecidae) across the ice-edge zone in the Weddell Sea,Antarctica

Choanoflagellates are thought to be an important component of oceanic microbial food webs, but little quantitative data exists on their abundance,, distribution, or relationship to potential food sources. In an Antarctic ice edge zone (northern Weddell Sea, March 1986), choanoflagellate abundance varied over two orders of magnitude in the upper 100 m. The lowest abundances were recorded at the bottom of the water column under ice cover and the highest abundances occurred in the upper 30 m of open water. Species that were predominantly in colonies dominated the open-water samples. Abundances of total choanoflagellates and some individual species were correlated with primary and secondary biomass and production, indicating a response to gradients in potential food sources. This suggests that choanoflagellates are tightly coupled with their food sources and supports the contention that they may an important link between bacteria-sized particles and metazoan grazers.