An analysis of internal phosphorus loading in Spring Lake, MI was conducted during August 2006, eight months following an alum treatment. Sediment cores were removed from 4 sites (that had been sampled previously in 2003 and 2004) and incubated in the laboratory under aerobic (with oxygen) and anaerobic (without oxygen) conditions. Phosphorus flux from the sediments into the overlaying water column were measured over a 22-day period and compared to rates measured from sediment cores collected previously from these sites. Field measurements showed reduced soluble reactive and total phosphorus concentrations the summer following the alum application, but chlorophyll and irradiance levels were not significantly affected. It is unclear if more frequent sampling would detect differences. Overall macroinvertebrate density declined significantly in 2006 compared to 2004, with chaoborids and oligochaetes experiencing the greatest reductions.


Spring Lake, Michigan, Sediment Control, Alum, Phosphorus


Environmental Monitoring