chapter  3
30 Pages

Sources and Fates of Nitrogen in Virginia Coastal Bays

Coastal bays, which are typically shallow, located in the photic zone, and have little freshwater input, respond differently to nutrient enrichment than do deeper estuaries. Because of the diversity of benthic and pelagic autotrophs they support, coastal bays are capable of modulating the effects of nutrient enrichment, derived from both allochthonous and autochthonous sources. We describe a study performed in Hog Island Bay, Virginia, located along a eutrophication gradient on the Delmarva Peninsula, to determine sources, sinks, and fates of nitrogen (N). On an annual basis, allochthonous sources of N, mainly base flow and atmospheric deposition, contributed 13%, whereas organic N remineralization (NRemin) in the sediments, supplied 77% of the total N available to support primary production. On a daily basis, N released by NRemin approximated the demand by benthic micro algae. Annually, N demand by benthic micro algae accounted for 55%,

Abstract ............................................................................................................................................ 43 3.1 Introduction ............................................................................................................................44 3.2 Sources of Nitrogen to Coastal Bays ......................................................................................48