A Natural Phosphate Source for Lake Waccamaw,North Carolina,USA

A limestone outcrop along the north shore of Lake Waccamaw, North Carolina, is found to contain ca. 0.1 % phosphate by weight. Weathering processes have probably driven steady inputs of phosphate from this source throughout the lake's history, accounting for its near eutrophic state. The sediments of Lake Waccamaw are enriched with phosphate, particularly in the littoral zone near the outcrop. Chemical and biological processes apparently remove phosphate from solution rapidly, making detection of a soluble phosphate signal near the outcrop difficult. Management of nutrient inputs and water quality in Lake Waccamaw requires consideration of the effects of this in-lake source of phosphate. Other sources of phosphate, particularly in the lake's drainage basin, may be less important than previously thought.