Snails and Freshwater

Most snails are listed on the endangered list, especially freshwater snails. They started to decline in the twentieth century. Dams and other changes made to rivers courses's, as well as agricultural and industrial pollution has been quickly declining the number and diversity of freshwater snails. When the snails die, other species such as crawfish who feed on the snails, begin to decline as well. A major snail killer is river channeling and dredging. When a river is channeled or dredged, infrastructure is added to the river, which can crush snails. Also, chunks of rocks used by snails can be loosened, snail eggs are crushed and adult snails are buried. And when snails die, their rotting bodies create large amounts of nitrates. Many snail conservation efforts are being taken, including water pollution control, and prevention of bad channeling or dredging that might kill snails. Freshwater snails are herbivores, and pollution poses a problem to this. They mostly eat algae, but sometimes large water plants. Pollution kills these plants and algae, when the snails have no food they die. When the snails die, they release nitrates which cause overgrowing of the plants they once ate. The overgrown algae and water plants is harmful to the environment of the freshwater source. Also, the amount of food snails eat, relates to their reproduction. When there is less food to eat, the population of baby snails goes down, and the baby snails are already having enough problems with channeling and dredging.

Lake Erie is a large freshwater source, and it has been having problems lately. High phosphorous levels coming from pesticides and fertilizers that ran into rivers, along with multiple sewage outbreaks from other cities has all flowed into Lake Erie and caused an outbreak of Mycrocystis algae. This algae can cause cramps, nausea, diarrhea, and sometimes death. It also uses up oxygen and causes animals with gills to sort of suffocate. The range of its oxygen sucking can vary from hypoxia (little oxygen) or anoxia (no oxygen). When the algae is in high concentration it forms little blooms which turn the water green, and suck up oxygen when they decompose. The cells are colonial, meaning that they can group together to create a film of algae near the surface of the water. It cannot survive in very salty waters, which is why it flourished in Lake Erie, a freshwater lake. Only one third of all the types of Mycrocystis algae are toxic. When it blooms, it is usually because the water is warm and nutrient filled, phosphorous fuels the blooming better than most nutrients. The main cause of this outbreak was there were sewage treatment systems and not enough control on pesticides and fertilizers used in industrial farming.

There are two types of pollution, point source pollution, and non point source pollution. Point source, is where there is one pipe for example that is polluting, non point source is where there are multiple little pipes that all add up to pollution. Point source pollution is much easier to fix, but non point source is not so easy to stop. All though its strange, heat is pollution, so when power plants use water to cool down their facilities, they harm temperature sensitive organisms in rivers. Non point source pollution consists of pollution runoff from industries or small sources. Construction, sewage management, agriculture, and mining are large contributors to freshwater pollution.

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Johnson, Paul D. "Sustaining America's Aquatic Biodiversity - Freshwater Snail      Biodiversity and Conservation." Virginia Cooperative Extension. Tennessee      Aquarium Research Inst., Cohutta, GA, 1 May 2009. Web. 8 Feb. 2011.      <http://pubs.ext.vt.edu/420/420-530/420-530.html>.

Hicks, Sarah. "Pollution." LAKE SCIENTIST. Kent State U, 2010. Web. 12 Feb.
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