Effect of nitrogen and phosphorus loading on plankton in coastal plain blackwater streams

350 210 Stroud Water Research Center

Mallin, M.A., L.B. Cahoon, D.C. Parsons, and S.H. Ensign. 2001. Journal of Freshwater Ecology 16:455–466.

doi: 10.1080/02705060.2001.9665832


We used nutrient addition bioassays to examine the effects of organic and inorganic nutrient loading on stream planktonic chlorophyll and ATP in the Black River and Northeast Cape Fear River of North Carolina. Additions of ammonium, inorganic N+P, and urea produced significant algal increases during bioassays in spring and summer. Urea stimulated chlorophyll increases comparable to those of ammonium treatments, with similar algal taxa responding to both treatments. However, neither organic nor inorganic phosphorus additions stimulated significant phytoplankton responses. In contrast, both orthophosphate and glycerophosphate treatments significantly stimulated ATP productions year-round. On several occasions ATP production was stimulated by P additions without concurrent chlorophyll stimulation, while in the same experiments chlorophyll was stimulated by N additions only. These results demonstrated that nitrogen additions to Coastal Plain blackwater streams can support algal blooms during selected periods, and phosphorus loading can stimulate growth of heterotrophic microflora, which then become sources of labile biochemical oxygen demand in these waters.