Spatial and temporal variability of internal and external phosphorus loads in Mona Lake,Michigan |
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Authors: | Alan Steinman Xuefeng Chu Mary Ogdahl |
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Institution: | (1) Annis Water Resources Institute, Grand Valley State University, 740 W. Shoreline Drive, Muskegon, MI 49441, USA |
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Abstract: | A study was conducted in Mona Lake, a small eutrophic lake located in western Michigan (USA) to address the temporal and spatial
variability of external and internal phosphorus loading. External P load varied among subbasins, which was mostly related
to discharge, but also to land use. Black Creek, which drains lands with natural cover and agriculture, accounted for the
majority of flow, and total phosphorus (TP) and soluble reactive phosphorus (SRP) load, to Mona Lake. However, the relative
contribution of SRP load was greater in Little Black Creek, which flows through a mostly urbanized subbasin, than in Black
Creek. The relative importance of internal loading was strongly related to season, as internal TP loads contributed only ∼9%
of the overall P load in April 2005, but ∼68–82% of the overall P load in the summer and early fall seasons. Internal TP and
SRP loading was greater under anaerobic than aerobic conditions. Mean anaerobic TP release rates ranged from 0.80 to 15.56 mg P m−2 d−1, varying with site and season. Spatial variability in both internal phosphorus loading and sediment P concentration was also
evident. By taking into account the spatial and temporal variability of different loading sources, management practices can
be targeted to optimize nutrient source control strategies. |
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Keywords: | Eutrophication Nonpoint source pollution Phosphorus transport West Michigan |
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