A large amount of algae covers Coldwater Creek on Tuesday, the result of hypereutrophic activity common in Grand Lake and in many of the lake's tributaries. Hypereutrophic lakes are rich with nutrients that run off from surrounding land and characterized by frequent and nuisance algae blooms and low transparency. Brian Miller, assistant manager of Grand Lake St. Marys State Park, said such an algae bloom is not unusual for this time of year because temperatures had risen in days prior to Tuesday and there had been no rain to wash it away.