SEASONAL CHANGES OF BENTHIC FORAMINIFERAL ASSEMBLAGES INHABITING THE WESTERN ANTARCTIC PENINSULA SHELF

Polar ecosystems respond quickly to environmental changes and a better understanding of how marine ecosystems respond to seasonal changes in polar regions is crucial for assessments of ecological responses to environmental changes of the past, present, and future. Foraminifera are particularly sensitive indicators of environmental changes, and to better understand their responses to change, the SEASONS project (Seasonal Ecological Analysis of Seafloor Organic Nutrient Supplies) examined sediment core samples across surface productivity gradients in the northern Gerlache- southern Bransfield Straights region (Western Antarctic Peninsula) in April 2008 (during a period of surface productivity bloom) and again in July 2008 (period of low surface productivity) at water depths of approximately 600 and 1200 meters. Dominant species of foraminifera found in this region included: Pullenia bulloides, Astrononion echolsi, Bolivina pseudopunctata, and Globocassidulina sp. Bolivina psuedopunctata was the dominant species of sample sites 4,5, and 6. Foraminiferal assemblages at sites 4 ( Gerlache Straight 628m) and 6 (Gerlache Straight 1187m) show a decrease in total abundance from April to July while site 5 (Croker Passage 1206m) shows an increase in total abundance primarily due to an increase in abundance of Reophax sp., which does not seem to be adversely affected by decreases in food availability. Differences in assemblages appear to be related to changes in organic input over space and time. Results from this study yield important information about the responses of foraminifera to seasonal changes, seasonal productivity, and distributions of foraminiferal assemblages. This information will generate modern analogs for regional reconstructions of seasonal variability based on foraminifera found in the fossil record. This study also provides the first census of living foraminifera on these timescales in this region, and will provide critical baseline data for assessments of seafloor biodiversity and the impact of climate change on microfaunal ecosystems in the region.