I worked on an environmental project in Orlando where one of the downtown lakes had water that was almost deadly to get into and at certain times of the year (summer) the bacterial count was downright deadly to low resistance people. We were getting blamed for the bacteria count because the drainage pipe from the road ran into the lake. Having the big pocket and multiple studies later it was shown it was the ducks, geese and swans that were killing the lake. So we moved them off after counsel with the City and there was also cleanup. Well within a year the public later preferred feeding the animals to a healthy lake and the feed vendors complained about loss of revenue so the City went back to the old practice. Now its as dirty as it was before $200,000 was spent on cleanup.