Date of Award

Summer 1975

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

Anthony J. Provenzano

Committee Member

Paul K. Kirk, Jr.

Committee Member

Donald D. Adams

Committee Member

Loyal Bouchard

Call Number for Print

Special Collections LD4331.O35 S53

Abstract

Estimated annual net microbenthic algal production of an intertidal sandflat on Little Creek Inlet, Virginia Beach, Virginia, was 105 g C/m2. Seasonally, primary production was greatest during the summer and fall periods (38 and 49 g C/m2, respectively). Productivity was found to vary directly with water temperature and standing crop of benthic diatoms, and inversely with incident solar radiation and standing crops of sedimentary chlorophyll 'a' and 'c'. Orthophosphate and nitrate-N appeared to be limiting factors, nitrate-N more so than orthophosphate. Mean annual net photosynthetic efficiency (based upon total light) for the microphytobenthic community was 0.09%. Photosynthetic efficiency generally reflected growth and diminishment within the microbenthic algal community, and varied inversely with water temperature and incident solar radiation. There appeared to be a direct correlation between photosynthetic efficiency and the availability of orthophosphate and ammonia-N.

Estimated annual benthic community respiration was 72 g C/m2. Seasonally, community respiration was greatest during the summer and spring periods (29 g C/m2, respectively). On an annual basis, benthic community respiration was 41% of gross primary production. Respiration varied directly with water temperature and incident solar radiation. It was also believed to reflect increased heterotrophic activity.

The microphytobenthic community at Little Creek was dominated by pennate diatoms. The mean annual diatom cell count was 3.9 X 101- cells/m2. Mean annual sedimentary chlorophyll 'a' and 'c' concentrations were 43 and 19 mg/m2, respectively. The season of greatest growth and development within the microbenthic algal community was during the fall period. Diatom growth and chlorophyll development appeared to vary inversely with water temperature and incident solar radiation. The utilization of inorganic nitrogen and silica was indicated during periods of increased algal growth. Orthophosphate was also found to be an essential nutrient factor. Grazing pressure by heterotrophic organisms was thought. to have been a limiting factor during the early summer and spring seasons.

Net phytoplankton production within the study area at Little Creek was negligible in comparison to that of the microphytobenthic community (-50 g C/m2/yr vs. 105 g C/m2/yr, respectively). However, oxygen demand by the plankton community exceeded that of the benthic community (96 g C/m2/yr vs. 72 g C/m2/yr, respectively).

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DOI

10.25777/95vp-g009

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