Comparison of Estuarine Salinity Gradients and Associated Nekton Community Change in the Lower St. Johns River Estuary

• Published in: Estuaries and coasts 2012-11, Vol.35 (6), p.1443-1452
• Main Authors: Guenther, Cameron B., MacDonald, Timothy C.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Aquatic habitats; Biological and medical sciences; Brackish; Brackish water ecosystems; Coastal Sciences; Community structure; Earth and Environmental Science; Ecology; Ecotones; Environment; Environmental Management; Estuaries; Estuarine ecosystems; Fish; Fisheries management; Fresh water; Fresh water ecosystems; Freshwater & Marine Ecology; Fundamental and applied biological sciences. Psychology; Marine; Nekton; Principal components analysis; River water; Riverine habitats; Rivers; Salinity; Species; Surface water; Synecology; Water and Health; Water resources; Zonation
• ISSN: 1559-2723; 1559-2731
• DOI: 10.1007/s12237-012-9544-5

Salinity is an important determinant of estuarine faunal composition; previous studies, however, have indicated conflicting accounts of continuous vs. relatively rapid change in community structure at certain salinities from geographically distinct estuaries. This study uses a large fisheries monitoring database (n>5,000 samples) to explore evidence for estuarine salinity zonation by nekton in the lower St. Johns River estuary (LSJR). There was little evidence to support the presence of estuarine salinity zones except at the extremes of the salinity gradient (i.e., 0.1–1.0 and 34–39). The LSJR estuarine nekton community exhibits progressively slow ecological change throughout most of the salinity gradient with rapid change at the interfaces with fresh and marine waters—an ecoline bounded by ecotones. This study affirms the rapid change that occurs at the extremes of the salinity spectrum in certain estuaries and is relevant to efforts to manage surface water resources and estuarine ecosystems. Given the disparity in the results of the studies examining biological salinity zones in estuaries, it would be wise to have, at minimum, a regional understanding of how communities are structured along the gradient from freshwater to marine.