An analysis of internal phosphorus loading in White Lake, MI was conducted during the summer, 2006. Sediment cores were removed from 4 sites in White Lake and incubated in the laboratory under aerobic (with oxygen) and anaerobic (without oxygen) conditions. Phosphorus flux from the sediments into the overlaying water column was measured over a 27-day period and compared to rates measured from sediment cores collected previously from Mona and Spring Lakes.

Internal phosphorus loading in White Lake sediments ranged from 1.55 to 7.78 mg TP/m2/d in anaerobic conditions and from -0.18 to 0.14 mg/m2/d in aerobic conditions. The negative value suggests that the sediments in some areas of White Lake could act as a sink for TP during aerobic periods. These internal loading rates were generally similar to summer measurements made in Mona Lake in previous years but considerably lower than those measured under anaerobic conditions in Spring Lake in 2003.

Internal total loading contributed 1.24 tons of phosphorus based on our laboratory study, with about half coming from the eastern-most basin in White Lake. Compared to an estimated external total phosphorus load of 15.48 tons/yr (Mark Luttenton, GVSU, unpublished data), internal loading of TP accounts for ~7.4% of the total TP load entering White Lake. This percent is much lower than what has been measured in Spring and Mona Lakes, suggesting internal phosphorus loading is a less important process in White Lake than nutrients entering from groundwater or surface inflows. These data suggest that management strategies should be focused, at least initially, on reducing external phosphorus loads to White Lake.


Lake Sediments, Ecosystem Health, White Lake, Michigan


Environmental Monitoring