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Patterns of Distribution of Estuarine Organisms and their Response to a Catastrophic Decrease in Salinity
Larsen, Peter F.
Larsen, Peter F.
Abstract
The occurrence of Tropical Storm Agnes during an ongoing study on the community structure of the macrobenthos associated with the James River oyster reefs provided a unique opportunity to document the responses of this assemblage to such a disturbance. The spatial and temporal patterns of abundance of 18 important taxa are examined in this paper. Eight species exhibited limited up estuary penetration, six were most successful in the upper part of the estuarine segment studied, two were most abundant in the mid-section of the study area, and two were ubiquitous. In the post-Agnes period, .six species exhibited reduced population levels, three experienced population increases, three became relatively more abundant at the down estuary sites and reduced at the up estuary sites, three became relatively more abundant at the up estuary sites and reduced at the down estuary sites, while no significant response was shown by three others. Hypothetical response categories are advanced to explain these responses. The freshet arrived and removed stenotopic species (category 1 response) which allowed others to fill the void in abundance (category 2 response). Other species essentially extended their range downstream where conditions were not optimal but were reduced in their original range because of the physiological stress caused by very .Low salinities (category 3 response). With the return of higher salinities the larvae of more stenohaline species settled where there was open space, i.e., at the up estuary sites (category 4 response). Some species showed no significant changes in abundance (category 5 response).
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1976
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Chesapeake Research Consortium
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LARSEN.pdf
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Virginia Institute of Marine Science