Effect of Sediment Transport on Benthic Bacterial Growth andExoenzyme Production

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Factors believed to stimulate bacteria in marine sediments, and therefore to enhance their role(s) in benthic communities and nutrient cycles, include increased nutrient supply, grazing pressure, and physical transport events. Dr. Deming's research will determine the effects of sediment transport on two key bacterial parameters, growth and exoenzyme production, in initially simplistic and progressively more complex simulations: static (single core), gradostatic (multiple cores linked in series across nutrient gradients), and hydrodynamic (flume) microcosms. Growth will be assessed in microcosms subjected to a defined sediment disturbance (and in undisturbed and killed controls), according to temporal and spatial shifts in bacterial abundance, biovolume, and frequency of dividing cells, determined by epifluorenscence microscopy. Exoenzyme activity will be measured using fluorescent substrate analogs. Both processes will be cross-checked in selected experiments using radiosotopic approaches. A major goal is to document the degree to which physical disturbance of quiescent sediments influences subsequent bacterial parameters (which, in turn, influence food resources for higher trophic levels), ultimately building a basis for predicting effects of sediment transport events in natural marine sediments.