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Green Bay: Spatial patterns in water quality and landscape correlations
Citation:
Yurista, P., J. Kelly, A. Cotter, S. Miller, AND J. VanAlstine. Green Bay: Spatial patterns in water quality and landscape correlations. JOURNAL OF GREAT LAKES RESEARCH. International Association for Great Lakes Research, Ann Arbor, MI, 41:560-572, (2015).
Impact/Purpose:
This paper takes a comprehensive look at water quality across the entire Green Bay of Lake Michigan. Extensive sampling with point samples and towed electronic instrumentation provided a thorough picture of the water quality in Green Bay that allowed for local, regional, and whole embayment statements on condition. Historical data which included past spatially extensive EPA water sampling of Green Bay allowed us to examine trends over time along the full embayment. Assessment and accountability for efforts to remediate areas of concern (AOCs, Lower Green Bay-Fox River, Menominee River) show progress in some water quality parameters out into the bay while anthropogenic stress continues to impact other water quality parameters across the entire bay. Conditions showed signs of improvement in the inner bay for total phosphorous and chlorophyll a and a decline across the entire bay in specific conductivity and chlorides.
Description:
We conducted a high-resolution survey along the nearshore (369 km) in Green Bay using towed electronic instrumentation at approximately the 15 m depth contour, with additional transects of the bay that were oriented cross-contour (49 km). Electronic sensor data provided an efficient characterization of spatial pattern in water quality parameters. Nearshore water quality was correlated with adjacent landscape characterization. The regressions were able to explain over 80% of the alongshore variability for some parameters. The parameters with the strongest correlation were specific conductivity, beam attenuation, and chlorophyll. A clear feature of Green Bay is the loading and stress introduced by the Fox River at the head of the bay. River loading sets up the conditions for a longitudinal gradient along the bay. The gradient has persisted since first observed in monitoring surveys decades ago in spite of rapid flushing of the bay and remedial actions to restore areas of concern (AOCs). The water quality gradient was steepest in the inner most 25 km of the bay followed with still a strong gradient to about 70 km and finally with a more gradual slope to where the bay joins Lake Michigan. We combined both recent (National Coastal Condition Assessment 2010) and past spatially extensive EPA water sampling of Green Bay to examine trends over time along the full embayment. Condition across the entire bay showed mixed signs with improvement in the inner bay for total phosphorous and chlorophyll a and a decline across the entire bay in specific conductivity and chlorides.
