That all sounds pretty depressing! But here are two good facts - (1) the pollutants entering our watersheds have been greatly reduced over the past twenty years, and (2) you can keep the progress going. We're not done yet!
We have talked about some of the "Big Time" polllution sources and which pollutants they discharge. Now let's look at what some of these pollutants do to the water and to the organism living in or drinking the water.
Chemical Pesticides: Some of the pesticides that enter streams are eventually consumed by fish and other organisms with their food and water. Plants and animals cannot use these chemicals, but they don't have any way to get rid of them, so the chemicals get stored in the fatty tissue of the organisms. Storing these chemicals wouldn't be a problem if there was only a little. But as one organism in the food chain eats another, the chemicals get passed along, and become more and more concentrated. The concentration of chemicals can get so high that it kills the organisms, or keeps them from effectively reproducing. For example, high concentration of DDT (a pesticide) will cause the egg shells of many species of birds to be thin. The shells of these bird species sometimes become so thin that the shells crack when the mother tries to incubate the eggs.
Fertilizers and Excessive Nutrients (human and animal waste): Fertilizers, human waste and animal waste all contain a lot of nutrients that plants need to grow. At first that sounds good, but when a lot of these nutrients enter a stream, pond, river, etc.... at the same time and place it causes a lot of phytoplankton or algae to grow. This is what is happening when you see a pond covered with what looks like slimy green stuff. When all of these plants begin to die they are broken down by bacteria. Since there are a lot of plants, there are a lot of bacteria. The bacteria use oxygen in breaking down the algae and phytoplankton and the amount of oxygen in the water can dramatically decrease. This drop in the amount of oxygen in the water makes it difficult, or maybe impossible, for other species to live there.
Pathogens: In addition to having a lot of nutrients in them, human and animal wastes also contain many different kinds of pathogens (disease causing organisms). As is the case with pesticides, organisms in the water ingest the pathogens with their water or food. The pathogens might kill the organisms that ingest them, make them sick, or simply be passed along to other organisms.
Oil, Chemicals and Heavy Metals: Like the other pollutants, oil, chemicals and heavy metals get ingested by the organisms that live in our water. These pollutants can have a lot of different effects on organisms and, unfortunately, they can all be toxic (kill the organism). Oil doesn't even have to get into the organism in order to harm it. For example, oil can get in the gills of fish and suffocate them. Ducks and other waterfowl can be injured or killed when oil gets on their feathers. The oil sticks their feathers together and ruins the natural oil coating that protects the birds from the water and cold temperatures.
That all sounds pretty depressing! But here are two good facts - (1) the pollutants entering our watersheds have been greatly reduced over the past twenty years, and (2) you can keep the progress going. We're not done yet!