Spatial distribution of bacterioplankton biomass and production in the marginal ice-edge zone of the Weddell-Scotia Sea during austral winter
Marine Ecology Progress Series
Recent investigations in the marginal ice-edge zone (MIZ) of the western Weddell and Scotia Seas revealed similar distributions of primary and microbial production in spring and autumn. Yet, little is known about the distributions of bacterial biomass and production in winter, and how these distributions may be influenced by local physical oceanographic features or interrelated to other chemical and biological distributions in the M1Z. To help elucidate the ecological and biogeochemical
... geochemical significance of bacterial production in winter, we examined the distributions of bacterial biomass and production in the MIZ of the Weddell-Scotia Sea in austral w~nter 1988 as part of the Antarctic Marine Ecosystem Research at the Ice-edge Zone (AMERIEZ) program. Measurements were made along 3 rapid transects providing a synoptic view of the MIZ. Transects were oriented normal to the ice edge with stations extending up to 100 km into the pack and several hundred km seaward of the ice edge. Winter distributions of bacterial biomass and production were more closely related to local hydrography than to microalgal distributions or the proximity of the ice edge Bacterial characteristics were highest within or in the proximity of warm-core eddies, enrichments which may have resulted from prior ice melt or from advection of more productive waters. Microalgal characteristics and bacterial production were at their seasonal minimum during the winter cruise; however, bacterial biomass was essentially invariant seasonally and was not as greatly influenced by the location of the ice edge as previously demonstrated for phytoplankton. Sirmlar reports for micrograzers suggest that steady-state conditions apply to much of the microbial food web throughout the year. Bacterial production did not dominate ammonium remineralization processes in winter; instead, ammonium maxima under the ice and near the ice edge were attributed to protozooplankton and higher trophic organisms.