Chemical Modulation of Marine Deposit Feeding

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Deposit feeding is important in gating the transfer or burial of all particles that arrive at the seafloor, with implications ranging from flow through trophic webs to resolution of the stratigraphic record. The resources that fuel deposit feeding, however, remain poorly identified-with a few notable exceptions. By chemical examination and biological experimentation that isolate the processes of food detection and digestion this project will attempt to generalize the approach used to create a pair of those exceptions. This project will be guided by theory that predicts maximization of net absorption rate as material transits the gut of an organism. The focus of the project is on three specific processes that modulate processes leading to this maximization, namely smell, taste and absorption across the gut wall. Smell and taste will be determined with chemical, operational definitions based on response to diffused or contacted compounds. The efficacy of compounds that elicit feeding responses in the laboratory will be tested for their roles as attractants in the field. While the correlation between sensing ability and nutritional value will not be perfect, the imperfection affects the ability of these animals to sense the presence of food and so itself is of interest. The concept of optimal gut retention times of ingested food focuses attention on a kinetic definition of food quality, whose determination will also likely result in identification of usable food resources. Measurements of absorption of digested foods into the gut wall will allow explicit tests of these models of absorption maximization on a series of animals from Puget Sound and the Gulf of Maine.