Seasonal fluctuations of benthic macrofauna (> 500 (mu)m) in the oligohaline East Bay region of the Apalachicola estuary were examined. Multivariate analyses of long-term (42 - 72 months) data from five soft-bottom stations identified three physico-chemical variables (river flow, water temperature and salinity) that were correlated with abundances of dominant macrofaunal species (six polychaetes and one amphipod). However, among station inconsistencies in the responses of these species to environmental variables suggested that additional factors, such as biotic interactions, are important. / Macrofaunal densities peaked during winter months, followed by a rapid decline during late winter/spring. Minimum densities occurred during the summer. The spring decline coincided with an influx of bottom-feeding fishes (Leiostomus xanthurus and Micropogonias undulatus). To test the hypothesis that these fishes were responsible for macrofaunal reduction, predator exclusion experiments were conducted at two unvegetated shallow subtidal East Bay stations. A preliminary study was conducted to design cages (mesh size = 6mm) that produced minimal physical and chemical artifacts. These were used with two-sided controls and uncaged controls in short-term (two month) exclusion experiments to test the effects of bottom-feeding fishes in the spring and Penaeus setiferus in the fall. During 1980, large motile predators were not important in regulating the densities of most macrofaunal species. Densities of L. xanthurus and P. setiferus were lower than in previous years. Despite reduced abundance of bottom-feeding fishes, macrofaunal densities still declined during late winter/spring. Three polychaetes, Mediomastus ambiseta, Streblospio benedicti and Hobsonia florida, accounted for a considerable portion of the late winter reduction in density. Recruitment data from defaunated sediments revealed a low abundance of H. florida and S. benedicti larvae, and virtually no M. ambiseta larvae, in the spring. Thus, lack of larval recruitment contributed to the decline of these short-lived species. It is postulated that increased river flow and lowered salinities during late winter/spring may contribute to the decline of macrofaunal densities by reducing larval recruitment. / Source: Dissertation Abstracts International, Volume: 43-06, Section: B, page: 1723. / Thesis (Ph.D.)--The Florida State University, 1982.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_74866 |
| Contributors | MAHONEY, BRUCE MICHAEL., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 127 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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