Areas around Michigan, including in Jackson County, have had reports of algal blooms on lakes and rivers. This algae can contain bacteria that could make you sick.  In June, an algal bloom on Portage Lake tested positive for this bacteria, cyanobacteria.  There is no specific treatment only to let the water clear, so the best advice is to avoid them and choose areas where there is no visible scum or film on the water.  To learn more about what is an algal bloom and what to do if you see one, read this press release from the State of Michigan.