Measuring Changes in Nutritional Status, Growth Rate, and Reproductive Condition of Deposit Feeders in Response to Sediment Transport - Methods

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Sediment transport is a ubiquitous oceanographic process. Theoretical models and limited laboratory studies indicate that sediment transport influences the quantity and quality of organic matter supplied to benthic deposit feeders, but the magnitudes and directions of the influences (i.e., positive or negative) in the field are essentially unknown. If sediment transport acts to enhance food resources, the response by deposit feeders might be manifested as increased individual growth rates, by accumulation of energy storage products, or by increased reproductive output. Conversely, negative responses in these properties should be seen if sediment transport adversely affects food resources. Such responses might occur singly or in various combinations. Methods to measure these parameters in animals collected from the field are needed in order to provide realistic tests of hypotheses about the effects of sediment transport on the energetics of deposit feeders and ultimately, on population dynamics. To begin moving in this direction, Drs. Taghon and Prahl will determine how nutritional status, growth rate, and reproductive condition of several species (including echinoderms, polychaetes, and molluscs) vary under different laboratory feeding regimes. They will measure changes over time in 3 properties to evaluate their use in tracking the response of deposit feeders to sediment transport: the accumulation or use of lipid stores (index of nutritional status), RNA:DNA ratios (index of growth rate), and reproductive condition.