The sample on the left was collected from the outflow pond of the Georgia Pacific plant on St. John's River, Florida. The right sample came from Back River, MD near Baltimore. Closterium is usually found in the benthic layer of acidic, oligotrophic lakes and ponds, but occassionally appears in estuarine rivers with little or no salinity. There are approximately 140 different species in this genus. See Wehr and Sheath in Taxonomic References.