Various stable-isotope studies indicate that benthic microalgae (BMA) contribute substantially to the energetic foundation of coastal food webs, even in salt marshes where production by vascular plants is comparable to or greater than that of BMA. Relatively little is known, however, about how primary consumers exploit BMA biomass or how they respond to variation in BMA availability. Nor do we have a clear understanding of how nutrients and grazing influence BMA productivity and standing stock. Accordingly, this research project will employ a seasonal, field-manipulative-experimental approach to examine interactions between BMA and the benthic metazoan consumers in a coastal salt marsh. The objectives of this research are to (1) Determine how nutrients and grazing limit BMA biomass and/or productivity, and (2) Determine how availability of BMA influences grazer condition and feeding activity. To accomplish these objectives, nutrient (NH4+ & PO;3) concentration and arthropod grazing pressure will be manipulated in a factorial experiment designed to detect the main effects of nutrients and grazing on BMA, and the interactions between the two. Similarly, the response of benthic grazers to variation in BMA food availability will be determined by manipulating light and nutrient availability. Field experiments will be repeated seasonally over a 3-year period to determine seasonal and annual variation of BMA-grazer interactions.
