STP988

    Effects of Complex Effluents on Photosynthesis in Lake Erie and Lake Huron

    Published: Jan 1988


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    Abstract

    Phytoplankton are the base of the food chain in most large lake ecosystems; if affected by environmental pollutants, significant ecosystem changes can result with potential impact on higher trophic levels. This research determined the effects of a complex effluent discharge from the River Raisin in Monroe County, Michigan, on the Lake Erie ecosystem. This river flows through southern Michigan and has large nutrient and industrial inputs, especially in the Monroe Harbor area. The functional parameters measured were bacterial uptake rate of acetate, zooplankton feeding and reproduction rates, and primary production. The results of the effects of complex effluents on gross photosynthesis, measured as carbon-14 (14C) uptake, are presented in this paper.

    Intensive sampling was undertaken during the ice-free seasons of 1983 and 1984. In 1983, water from various stations in the River Raisin was mixed with eutrophic Lake Erie water at several dilutions. The rate of photosynthesis in the mixed samples was compared with with that of a control composed of Lake Erie water only. No clear trend in photosynthetic response was evident with increasing percentages of river station water. In 1984, oligotrophic Lake Huron water was substituted as the control, resulting in massive stimulation in photosynthesis with increasing percentages of river station water. There were increased levels of nutrients, toxicants, and algal biomass in the harbor area in relation to the Lake Huron control. The 1984 data were evaluated again after being weighted for the relative biomass of algae as 14C uptake, so that a nutrient-toxicant interaction could be examined. Using these simple linear mixing criteria, a gradient in toxicity was found, with the upstream area of the river causing stimulation of photosynthesis while the harbor stations caused inhibition at all concentrations of effluent. Extensive chemical and physical analyses were done on the station effluents and controls. An analysis of covariance on the 1984 data indicated that no single toxicant was responsible for the inhibition of photosynthesis found in the harbor area.

    Results suggest that, in complex effluent tests when an oligotrophic control is used with eutrophic effluents, a weighting factor for the relative biomass of algae must be used. Predictable trends occurred when this was done in relation to the Lake Huron control. Tributaries with diverse anthropogenic inputs, such as the River Raisin, have the potential for significant inhibition of primary production in receiving bodies of water.

    Keywords:

    complex effluents, photosynthesis, River Raisin, Great Lakes, nutrient-toxicant interactions, weighted algal biomass


    Author Information:

    Bridgham, SD
    Graduate student, School of Forestry and Environmental Studies, Duke University, Durham, NC

    McNaught, DC
    Professor and technician, University of Minnesota, Minneapolis, MN

    Meadows, C
    Professor and technician, University of Minnesota, Minneapolis, MN


    Paper ID: STP26257S

    Committee/Subcommittee: D19.05

    DOI: 10.1520/STP26257S


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