Bacteria-contaminated beach sand will be one of the leading topics of the Great Lakes Beach Association when it begins on Tuesday in Porter, at Indiana Dunes National Lakeshore (INDU) and Indiana Dunes State Park (IDSP).

Recent research, much of it conducted by the Lake Michigan Ecological Research Station of the U.S. Geological Service (USGS) at INDU, has shown that beach sand contains high levels of E. coli and other fecal indicator bacteria, in amounts often greatly exceeding the concentration in lake water itself. There is further evidence that beach closings due to elevated fecal indicator bacteria may be linked to these sand populations. Contaminated sand, accordingly, can complicate swimming-water monitoring.

“Over the last few years, we’ve identified an important source of indicator bacteria and how these bacteria may negatively influence recreation, but this is the first time experts have actually met to discuss this issue collectively,” said Richard Whitman in a statement released by USGS on Friday. Whitman was among the first to describe these high concentrations of E. coli in sands and link them to high bacteria counts in water.

Beach water is routinely analyzed for E. coli and other fecal indicator bacteria to determine whether human sewage is present. When bacteria concentrations in water exceed a certain threshold, beaches are typically closed to swimming or swimming advisories are posted. Nationwide, USGS said, beach closings are a persistent problem and efforts to minimize closings often unsuccessful. “For most beach closings, the reason for high bacteria concentrations remains unknown.”

But a potential reason for many of the beach closings, and a complication for monitoring efforts, is high concentrations of fecal indicator bacteria in sand. “Bacteria are often present in high concentrations independent of any recent contamination,” USGS said. “Further, bacteria are often re-suspended into the beach water during onshore winds and high waves. The health risk associated with these bacteria is yet unknown but preliminary studies are being conducted.”

The Great Lakes Beach Association conference will include experts from agencies and universities from California, Florida, Michigan, Indiana, Hawaii, and Canada. USGS is hosting the event.

Posted 9/15/2008