Have you ever seen a stream that looks dirty? This dirty look is usually caused by the excessive erosion of silt or sediments from nearby lands. Silt or sediment is fine particles of soil that end up in our waters. A small amount of sediment reaching the waters is natural.However, surface mining, timber harvest, construction, and poor farming practices can leave soil unstable. Then, when it rains, the soil is carried off by the water, which eventually runs into a river or lake. There are modern methods of farming, logging, and mining that minimize erosion.
When it settles to the bottom it has a smothering effect. It can kill plants or other small organisms. It can smother fish eggs and young aquatic life. It can cover up the rocks where the fish's food lives. If the silt does not settle, the water ends up with a dirty look. This muddy water does not allow light to pass through for use by plants and other aquatic life. The result is a ruined body of water that no longer supports the fish we want to catch.
Agricultural wastes include manure, liquid and granular fertilizers, silo liquids, and pesticides. Cattle, hogs, sheep and poultry raised on feedlots are a big problem. They concentrate a lot of wastes over a very small area. One cow produces as much waste as 17 people every day. Some of this waste is washed directly into rivers. In addition, farmers spread manure and fertilizer on their open fields that may eventually enter a body of water. Pesticides are chemicals used to help farmers control pests that ruin their crops. If properly used they generally create little or no problem. However, when they enter a water system through careless use, they usually cause environmental damage by killing fish and other organisms in the water.
Sewage consists of human wastes and garbage. It also includes water used for laundering or bathing. Most sewage is treated at a treatment plant that removes the solids and dissolved substances. However, when a treatment plant gets overloaded or has a malfunction, sewage gets dumped into rivers. Today's laws are quite strict, but sewage pollution is still a major problem, especially in large cities. Sewage depletes the dissolved oxygen in water. Sewage wastes contain nutrients that serve as fertilizers. They cause algae (tiny plants) to bloom in great quantities. When these organisms die, oxygen is used for the process of decomposition, and the fish go without adequate oxygen and sometimes die. If this situation gets bad enough, all the fish in a river below a treatment plant may die. As you have learned, fish must have an adequate supply of oxygen or they will not survive. Raw sewage can also cause serious diseases in humans who use the water or eat shellfish from polluted areas. Sewage may also make waters unhealthy to swim in.
Accidental oil spills can have disastrous effects on aquatic life. Petroleum products can kill by direct contact with the fish's gills. Oil may also suffocate eggs and young fish, since the young inhabit shallow waters where oil tends to concentrate. Marine birds, sea otters and turtles may also be killed.
We have become a throwaway society and are running out of dumps to put our trash. Some people do not even try to dispose of their trash appropriately and throw it in and along our waters. No one enjoys fishing or swimming when having to contend with broken bottles, sharp cans and other trash. Sinking cans, bottles or other trash in the water may put them out of sight temporarily, but they are still there and it is still wrong. Plastics are particularly hazardous. They are not easily biodegradable and will be around for a long time, maybe for hundreds of years. Thousands of fish and birds die every year from entanglement in plastic six-pack rings that come from canned drinks. Nylon fishing line discarded by thoughtless anglers can also kill birds by entanglement. Some sea turtles even mistake plastic bags for jellyfish (their favorite food) and choke to death when they eat a plastic bag by mistake.
Nuisance species are living organisms that upset the delicate balance of a particular body of water. These may be considered biological pollutants. Not all bodies of water are the same. Even lakes close together may have different characteristics. In some bodies of water a particular type of fish may be part of the balance. However, in a different body of water that same species may throw off the entire balance. The same is true of some types of vegetation and other aquatic life. Some types of vegetation may prove helpful in one lake and a disaster in another. For example, crappies are excellent sport fish and in many lakes they fit in well with the balance of the lake. However, if put into a different setting the crappie could ruin the entire lake. In the wrong setting the crappie could populate faster and compete for food and space. You could end up with a lot of little crappie and little else. Certain kinds of vegetation might be healthy for some water systems. In others, that same vegetation/weed might take over. Too much vegetation can interfere with boating access and protect too many small fish that will then cause an overpopulation of small fish. Also, when weeds die, they decompose removing oxygen from the water. When the oxygen level gets too low, fish will die. The Great Lakes have had many problems with unwanted species. One problem species introduced by way of ballast water from a ship, was the zebra mussel. The mussel reproduces rapidly. Biologically it is still not known what impact the mussel will have, but it could block spawning grounds for several native fish. The mussel also attaches itself to intakes of water supplies and power plants, causing millions of dollars in damages.
Major sources of pollution must be stopped if quality fisheries are to exist. Even the large oceans and estuaries of the world are fragile ecosystems that require attention and careful use to protect them for our future use and enjoyment. How will you feel if you go fishing and your favorite river is so polluted that the fish have died? We can all help. While many of these problems seem out of your hands, there are many problems you can solve in your area by getting your classmates, friends, and neighbors to vocally protest the problem. Our own actions on a daily basis are important. We each have a responsibility to make sure our own actions are not depleting or polluting the water. An individual action, either positive or negative may seem small. However, when you multiply that by millions of us who live in each state, these actions have a tremendous cumulative impact. Remember we all live downstream of someone.
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