Date Awarded

1978

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Advisor

George Grant

Committee Member

John A. Musick

Committee Member

William E. Odum

Committee Member

Craig Smith

Committee Member

Paul L. Zubkoff

Abstract

Zooplankton composition, distribution, biomass and biochemical constituents were determined monthly in the lower Chesapeake Bay for two years beginning in August 1971. Settled volume, dry weight, and ash-free dry weight estimates of total biomass were generally consistent in showing summer and late winter peaks. A mean dry weight peak of 258 mg/m3 in August 1971 decreased precipitously to a December low of 9 mg/m3, then increased to a March 1972 peak of 199 mg/m3. The second year mirrored this pattern, except that the passage of Tropical Storm Agnes in June 1972 lowered the summer peak values for July and August considerably. In August 1971 and again in August 1972, a total of 53 species, from four dominant major groups, were used to characterize four distinct geographical cluster zones. The summer zooplankton was dominated by cladocerans, largely Penilia avirostris and Evadne tergestina, and the copepod Acartia tonsa. Decapod larvae proved to be the most diverse summer group studied, containing 30 species in August 1971 and 33 species in August of 1972. Dominant species included Upogebia affinis, Callinectes sapidus, and Uca sp. Chaetognath peaks in September of each year consisted almost entirely of Sagitta tenuis. Winter populations contained less than half the number of taxa as summer zooplankton and were dominated by Acartia clausi. This species almost completely replaced Acartia tonsa by April of each year. The most notable effects of the lowered salinities caused by Tropical Storm Agnes in the summer of 1972 were a drastic reduction in cladoceran abundance and a compression of chaetognath distribution to the higher salinity areas near the bay mouth. Protein, the largest organic fraction of the zooplankton, usually accounted for 40-60% of the total dry weight. Mean monthly lipid values ranged from 1.9 to 9.5% of the dry weight, and carbohydrate appeared only as a minor organic fraction. This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia.

DOI

https://doi.org/10.25773/6KXX-0152

Rights

© The Author

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