A trend line for the entire period of record was calculated using

A trend line for the entire period of record was calculated using the negative exponential smoothing algorithm in SPSS SigmaPlot.

We calculated violations as the percentage of all samples collected during a single beach season that exceeded the relevant water quality this website standard for the time period. We constructed a time-table based on the collected data and literature sources of the key events in the socioeconomic and ecological systems, and assigned each event to one of the following categories: ecology, policy/governance, water infrastructure, human health, economics, human population, or climate (Table 1). Below we describe the findings for larger subsystems of the LSC area, including the climate, socioeconomic, and ecological systems. Lake St. Clair lies in a moist continental climate zone with cool summers and severe winters according to the Koppen climate classification (Kottek et al., 2006) (Fig. 2). Lake levels vary seasonally, with highest levels in June and lowest in January. In the 30-year period of 1972 to 2002, the lake was partially or completely covered by ice from November to the following April, and on average about

83% of the lake had ice cover during January (Fig. 2). There was a significant interannual variability in winter precipitation and air temperature, and hence in lake level and ice cover (Fig. 2). The winter of 1998–1999 had the highest air temperature and the lowest ice cover. Because March is the major melting period of lake ice, ice cover in March shows the greatest variation between years, with some years experiencing > 80% ice cover and other years Apoptosis inhibitor experiencing < 1% ice cover. There have been long-term changes in temperature, precipitation, lake levels and ice cover over the past 100 years (Fig. 2). Monthly air temperature

has been gradually increasing in the last 60 years (p < 0.001). The lake temperature in May PDK4 has shown significant increase since 1948 (p < 0.001). Using Great Lakes monthly hydrological data, the following significant trends for LSC have also emerged. Since 1900 the annual precipitation has increased by 0.03 mm yr− 1 (p < 0.05). From 1910 to 2012, lake water levels in LSC have been generally increasing in all seasons (p < 0.001) with the higher rate of increase during the winter and spring seasons. The highest lake water level occurred in October 1986 and the lowest water level in February 1926, and the average annual rate of increase in lake level is 4.3 mm yr− 1 (p < 0.05) over the period of record. But in the past two decades (1992–2012), the lake water level has been decreasing by 25.9 mm yr− 1 (p < 0.05). On the annual scale, lake water level was correlated with precipitation with a one-year lag (R = 0.44). The lack of a stronger correlation is possibly due to dredging in the St. Clair River and the impacts on the connecting channel flows (Quinn, 1985).

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