Seasonal Dynamics of Giant Agglutinated Foraminifera

Health Research Incorporated/New York State Department Of Health, Menands NY

Investigators

Abstract

A seasonal study of the dominant agglutinated foraminiferal assemblage in Explorers Cove, McMurdo Sound, Antarctica is the focus of this research. Studies have shown that the agglutinated foraminifera ("forams") at this locality consume a wide variety of prey, ranging from bacteria through a taxonomically diverse group of metazoans, including juvenile invertebrates. These studies have been restricted to specimens collected in October, November and early December, i. e., immediately following the Austral winter and before the summer burst of under-ice and benthic primary productivity. Little information is available regarding the foraminiferal response to this summer food pulse. The aim of this work is to utilize the planned extention of logistic support in the region. The Specific Aims of this proposal are: To document Austral spring to late- summer changes in relevant abiotic and biotic factors in the Explorers Cove benthos; and to characterize corresponding responses in agglutinated foram community structure (species composition, densities, size distribution). These first aims will be accomplished by traditional sediment coring, biomass determinations, and microscopic sorting methods. Additionally, an -situ approach for documenting fine-scale changes using novel underwater microscopy equipment will be utilized. Molecular tools to examine seasonal foram community dynamics initially focusing on the timing, of reproductive events multiple fission, gametogenesis will be perfected. Additional work will focus on newly refined sediment core embedding methods to explore the fine-scale seasonal changes in foram life position. In related lab experiments, the trophic mechanisms of the key agglutinated species will be analyzed. Time-resolved stable isotope analyses of lipids extracted from freshly collected and "snap frozen" forams will be used to determine if and how these mechanisms change in response to available food sources. These combined approaches will lead to a more complete understanding of the roles played by larger agglutinated forams in the Explorers Cove benthic food web, and how these roles change with respect to the summer food pulse. Because Explorers Cove and its agglutinated foram assemblage are closely comparable to many bathyal and abyssal deep-sea localities, the results of these studies will have wide significance in the ocean sciences.