DISTRIBUTION AND ABUNDANCE OF MINIPELLETS AROUND THE ANTARCTIC PENINSULA - IMPLICATIONS FOR PROTISTAN FEEDING-BEHAVIOR

During the 'European Polarstern Study' (EPOS) in the Scotia and Weddell Seas (SWS) and the XXVI Antarctic Chilean Expedition (INACH) in the South Shetland Islands area (SSIA), water and net samples were collected to assess the distribution, abundance, and role of minipellets in Antarctic waters. Two groups of minipellet producers, phaeodarian radiolarians and unarmoured dinoflagellates, were identified. The vertical (from surface to 100 m depth) distribution patterns of minipellets (5 to 100 mum) showed that the maximum concentration was located mainly between surface and 50 m depth in both the SWS and SSIA. On average, higher numbers of minipellets were found in the SWS (814 l-1) than in the SSIA (164 l-1). The most frequent and abundant silicified food items found in minipellets were diatom frustules. In phaeodarian radiolarians, the presence of partially ingested undamaged diatoms indicated that, in addition to feeding on detritus, phaeodarians also directly feed on phytoplankton. In both areas, higher numbers of minipellets occurred when the larger phytoplankton (> 25 mum) dominated the phytoplankton assemblage. Similarities between the diatom species composition in the water column and enclosed in minipellets suggest that grazing was non-selective.