MEPS 320:101-108 (2006)  -  doi:10.3354/meps320101

ABSTRACT: Increased residential development in coastal watersheds has led to increases in anthropogenic nitrogen inputs into estuaries. Sessile bivalves are good candidate organisms to examine nitrogen enrichment effects on consumers because they contribute significantly to material transport from pelagic to benthic systems. We examined condition index (CI), individual dry weight, density, and total biomass in the ribbed mussel Geukensia demissa (Dillwyn), from 10 marsh sites within Narragansett Bay, Rhode Island, subject to varying watershed sub-basin nitrogen loadings. We tested hypotheses that condition and population attributes of G. demissa are driven by watershed sub-basin nitrogen load. There was no clear relationship between the mussel CI and nitrogen load. G. demissa density and total biomass did increase significantly with increases in nitrogen load. Responses in individual mussel dry weight might be an indirect effect of increased nitrogen loading due to eutrophication-induced changes in food availability. Increased nitrogen loads could be increasing G. demissa food sources, such as Spartina alterniflora detritus, microheterotrophs, particulate organic matter, or phytoplankton, that subsequently translate into higher G. demissa growth and reproduction.

KEY WORDS: Bivalve · Nitrogen · Population attributes · Condition index · Indirect effects