Aquatic Sciences Meeting, Albuquerque 2001

SS31 Integrated Approaches to Drainage Basin Nutrient Inputs and Inland/Coastal Eutrophication (Science and Society Connections)

Date: Thursday, February 15, 2001, Time: 4:00:00 PM

Location: Cimarron

Dortch, Q, , Louisiana Universities Marine Consortium, Chauvin, USA, qdortch@lumcon.edu

Nelson, D, M, Oregon State University, College of Oceanic and Atmospheric Sciences, Corvalis, USA, nelsonda@ucs.orst.edu

MULTIPLE NUTRIENT LIMITATION: THE CONSEQUENCE OF BALANCED NUTRIENT INPUTS IN THE HIGHLY EUTROPHIC OUTFLOW REGION OF THE MISSISSIPPI/ATCHAFALAYA RIVER

Controlling coastal eutrophication requires an understanding of which nutrients ultimately become limiting. In the highly eutrophic outflow region of the Mississippi/Atchafalaya Rivers Justic et al. have proposed that nutrient inputs from the rivers are balanced with respect to phytoplankton growth requirements (Redfield ratios). Limitation by any particular nutrient may vary seasonally due to differences in input ratios. Simultaneous, multiple nutrient limitation was observed in 3 of 5 microcosm nutrient addition experiments (8 treatments in duplicate/per experiment) with natural plankton: two experiments showed N, P, and Si limitation (spring), one showed N and P limitation (summer), one exhibited primary P and secondary N limitation (spring) and one was primarily N limited and secondarily P limited (summer). The watershed has experienced drought conditions since fall, 1999, so these results may not be typical, but they point to the possibility of multiple nutrient limitation, which must be taken into account in management scenarios.

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Aquatic Sciences Meeting, Albuquerque 2001

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