Aquatic Sciences Meeting, Albuquerque 2001

SS33 Human Impacts and Activities on Riverine Ecosystems (Science and Society Connections)

Date: Thursday, February 15, 2001, Time: 10:00:00 AM

Location: Galisteo

Hatch, L, K, University of Minnesota, St. Paul, USA, hatch013@umn.edu

River plankton and phosphorus bioavailability in the Minnesota River, USA

Non-point source nutrient pollution is of great concern in the Minnesota River (MNR) basin. This 40,000 sq. km system is dominated by rowcrop agriculture, and contributes significant nutrient loads to the Mississippi River and the Gulf of Mexico. In the lower reaches of the MNR, mean monthly soluble reactive phosphorus and dissolved inorganic nitrogen values ranged from 57 to 150 µg/L and 2.82 to 7.09 mg/L, respectively. However, our understanding of the interaction between suspended sediment and plankton in the MNR is far from complete. The dominant algae in the lower MNR, Stephanodiscus hantzschii, was cultured and used in sediment bioassays. Suspended sediment from 17 tributary sites thoughout the MNR basin was collected during three late 1999 spring rain events. Each site was individually composited, and the dried sediment was used in bioassays to determine sediment bioavailable P (BAP). Results indicate that sediment BAP varies by a factor of two according to watershed of origin.

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Aquatic Sciences Meeting, Albuquerque 2001

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