SPATIAL-DISTRIBUTION OF BACTERIOPLANKTON BIOMASS AND PRODUCTION IN THE MARGINAL ICE-EDGE ZONE OF THE WEDDELL-SCOTIA SEA DURING AUSTRAL WINTER

Recent investigations in the marginal ice-edge zone (MIZ) of the weste rn Weddell and Scotia Seas revealed similar distributions of primary a nd microbial production in spring and autumn. Yet, little is known abo ut the distributions of bacterial biomass and production in winter, an d how these distributions may be influenced by local physical oceanogr aphic features or interrelated to other chemical and biological distri butions in the MIZ. To help elucidate the ecological and biogeochemica l significance of bacterial production in winter, we examined the dist ributions of bacterial biomass and production in the MIZ of the Weddel l-Scotia Sea in austral winter 1988 as part of the Antarctic Marine Ec osystem 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 extendi ng up to 100 km into the pack and several hundred km seaward of the ic e edge. Winter distributions of bacterial biomass and production were more closely related to local hydrography than to microalgal distribut ions or the proximity of the ice edge. Bacterial characteristics were highest within or in the proximity of warm-core eddies, enrichments wh ich may have resulted from prior ice melt or from advection of more pr oductive waters. Microalgal characteristics and bacterial production w ere at their seasonal minimum during the winter cruise; however, bacte rial biomass was essentially invariant seasonally and was not as great ly influenced by the location of the ice edge as previously demonstrat ed for phytoplankton. Similar reports for micrograzers suggest that st eady-state conditions apply to much of the microbial food web througho ut the year. Bacterial production did not dominate ammonium reminerali zation processes in winter; instead, ammonium maxima under the ice and near the ice edge were attributed to protozooplankton and higher trop hic organisms.