Coastal groundwater discharge – an additional source of phosphorus for the oligotrophic wetlands of the Everglades

Authors

René M. Price, Southeast Environmental Research Center and Department of Earth and Environment, Florida International UniversityFollow
Peter K. Swart, Rosenstiel School of Marine and Atmospheric Sciences, Marine Geology and Geophysics, University of MiamiFollow
James W. Fourqurean, Department of Biological Sciences and Southeast Environmental Research Center, Florida International UniversityFollow

Abstract

In this manuscript we define a new term we call coastal groundwater discharge (CGD), which is related to submarine groundwater discharge (SGD), but occurs when seawater intrudes inland to force brackish groundwater to discharge to the coastal wetlands. A hydrologic and geochemical investigation of both the groundwater and surface water in the southern Everglades was conducted to investigate the occurrence of CGD associated with seawater intrusion. During the wet season, the surface water chemistry remained fresh. Enhanced chloride, sodium, and calcium concentrations, indicative of brackish groundwater discharge, were observed in the surface water during the dry season. Brackish groundwaters of the southern Everglades contain 1–2.3μM concentrations of total phosphorus (TP). These concentrations exceed the expected values predicted by conservative mixing of local fresh groundwater and intruding seawater, which both have TPμM. The additional source of TP may be from seawater sediments or from the aquifer matrix as a result of water–rock interactions (such as carbonate mineral dissolution and ion exchange reactions) induced by mixing fresh groundwater with intruding seawater. We hypothesize that CGD maybe an additional source of phosphorus (a limiting nutrient) to the coastal wetlands of the southern Everglades.

Comments

Post Print Version.

Copyright © 2006 Springer.

The definitive publisher-authenticated version is available online at http://dx.doi.org/10.1007/s10750-006-0120-5

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Recommended Citation

Price, R.M., P.K. Swart, J.W. Fourqurean. 2006. Coastal groundwater discharge - an additional source of phosphorus for the oligotrophic wetlands of the Everglades. Hydrobiologia 569(1): 23-36.