Sources,sinks, and fluxes of nutrients (N + P) in a small highly modified urban estuary in southern California |
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Authors: | Fong Dr Peggy Zedler Dr Joy B |
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Institution: | (1) Department of Biology, University of California Los Angeles, 405 Hilgard Avenue, Los Angeles, CA, 90024-1606;(2) Department of Botany and Arboretum, University of Wisconsin, 430 Lincoln Drive, Madison, WI, 53706. jbzedler@facstaff.wisc.edu |
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Abstract: | Our objective was to begin to investigate sources, sinks, and flux rates of nitrogen (N) and phosphorus (P) in Famosa Slough, a small (12 ha) highly modified urban estuary in San Diego, California, U.S.A. The hydrology of Famosa Slough has been modified by culverts that dampen tidal influence and seasonal runoff from two urban watersheds, each of which has been implicated as a nutrient source that generates nuisance algal blooms. In 1995 and 1996, the ranges of nutrients measured in the water column were extremely wide; upper values exceeded those in other estuaries identified as eutrophic. Average dissolved inorganic nitrogen ranged from 2 to 250 M, while dissolved inorganic phosphorus ranged from <1 to 15 M. Nutrient content of the water changed rapidly both spatially and temporally depending on the tides and rainfall. While tidal water dominated this system, especially in the dry season, our results indicate that Famosa Slough's small watershed, not the larger watershed of the San Diego River, was the major source of nutrients during rainfall. Sediment nutrients were also high (3 mg N g dry wt–1 and 0.600 mg P g dry wt–1). Short-term flux studies suggest that the large accumulations of opportunistic green macroalgae commonly found in this estuary, and possibly the sediments, may act as a large and rapid sink for nutrients during times of high nutrient supply. We suggest that small, shallow estuaries in urban settings may have more complex and rapid nutrient dynamics than those found in larger systems. |
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Keywords: | nitrogen phosphorus macroalgae estuary anthropogenic |
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