Reconstructing the historical trophic status of northwestern Pennsylvania lakes using GIS

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2006-07-29
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Ostrofsky, Milton L.
Bradley, C.P.
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Keywords
trophic status , Phosphorus export , GIS , Pennsylvania lakes
Abstract
From each of 46 watersheds in glaciated northwestern Pennsylvania we estimated phosphorus export (kg P/ha/yr) from weekly or twice-weekly measured stream phosphorus concentrations and measured stream discharges, and determined land covers using GIS. Simple and step-down multiple regression analyses yielded models that explained 24% of the variation in P export using land cover within whole watersheds, and 64% of the variation using land cover within 200 m riparian buffers. We used these models to predict P loading to seven lakes and found that predicted lake [P] was consistent with measured lake [P]. To estimate pre-settlement lake [P] we reapplied the P export models with the assumption that human-impacted land covers were originally forests. Predicted (hindcast) pre-settlement lake [P] indicated that six of the seven lakes were edaphically mesotrophic (10 < [P] < 20 μg/l). Lake remediation targets set on the assumption that area lakes were historically oligotrophic ([P] < 10 μg/l) will be unattainable.
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Biology
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Ostrofsky, M.L. and Bradley, C.P. (2006). Reconstructing the historical trophic status of northwestern Pennsylvania lakes using GIS. Hydrobiologia 571: 273-281. doi:10.1007/s10750-006-0245-6
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Springer
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