Document Type

Conference Paper

Publication Date

1991

Publication Title

Proceedings of the Back Bay Ecological Symposium

Pages

20-28

Conference Name

Back Bay Ecological Symposium

Abstract

In order to help assess the cause of the recent decline in submersed macrophytes, light attenuation was measured at selected stations in Back Bay, Virginia, in July 1987 and April 1988, using an underwater spectroradiometer. Secchi depth and concentrations of total suspended solids and chlorophyll-a were measured simultaneously. In July 1987, extinction coefficients ranged from 2.7 to 5.7 m-1 and Secchi depths ranged from 0.26 to 0.44 m. Total suspended solids ranged from 27 to 64 mg/L--37 to 80% of the suspended material was organic matter. Chlorophyll-a concentrations ranged from 43 to 71 μ g/L; indicating the presence of large numbers of algae. Water clarity was least in North Bay and greatest at the North Carolina border. In April 1988, during a period of strong wind, total suspended solids were extremely high, ranging from 78 to 214 mg/L, whereas the organic fraction ranged from 20 to 30%. Chlorophyll-a concentration ranged from 34.5 to 88 μ g/L. Secchi depth ranged from 0.16 to 0.33 m and K ranged from 3.7 m-1 at the North Carolina line to 19.9 m-1 in a canal near Pellitory Point. Comparison of the conditions in Back Bay in 1986-88 with those in the tidal Potomac River and Estuary indicate that the decline in submersed macrophyte, in Back Bay is related to high light attenuation.

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