effects of pollution on lakes

Effects of water pollution on lakes

Water pollution affects the health of the waterway, the health of the organisms living in and around the

waterway, and, eventually, the health of humans. The effects of water pollution can range from aquatic

deformities to contaminated fish to "dead" lakes.

Aquatic diseases and deformities

As virtual "canaries in a gold mine," the deteriorating health of fish and wildlife speaks volumes

about the need to clean up the Great Lakes. Heavy metals such as mercury and lead, and human-

made organic chemicals such as pesticides, biomagnify as they move up the food chain, resulting

in tumors and death for predatory animals, such as lake trout, herring gulls, and even humans.

Toxic pollutants can also alter the genetic makeup of an organism, resulting in either death or

extreme deformities. Studies have found cormorants suffering from cross-billed syndrome at

rates 42 percent times the natural occurence, while terns exhibit birth defects from dioxin, PCBs

and furan exposure at 31 times the normal levels. Other examples of deformities include large

fish tumors and three-legged frogs.

Eutrophication

Before Europeans arrived in the Great Lakes region, the Great Lakes were mainly oligotrophic

lakes, meaning they contained little plant nutrients and were continuously cool and clear due

to their immense size and depth. Oligotrophic lakes can support high levels of animal life and

receive proper amounts of nutrients, mainly phosphorous and nitrogen, from natural sources,

such as decomposing plant matter.

European settlement and industrialization changed all of that. The amount of nutrients entering

the Great Lakes has intensified greatly, mainly due to increased urbanization and agriculture,

leading to increased biological growth, or eutrophication. Under eutrophic conditions, nutrient

loading (more nutrients than the waterbody can handle) stimulates excessive plant growth, which

in turn decreases the amount of oxygen in the water and eventually kills off certain species of

animal life. Other pollution-tolerant species, such as worms and carp, grow more rapidly; thus,

the ecological balance of the lake is significantly altered.

At one time, many people believed that water was capable of diluting toxic substances to the point of

rendering them harmless. However, we have since learned that this is not the case, especially in regards

to POPs, which persist in bodies of water -- no matter how diluted they are -- and accumulate in the

food chain. The United States and Canada realized that the health of the Great Lakes could be best

achieved through cooperation, and since the 1970s both countries have been working toward a cleaner

Great Lakes system.

Although phosphorus levels in lakes Ontario and Erie have decreased by almost 80 percent since the

1970s and many regulations have been placed on toxic chemical dumping, water pollution in the Great

Lakes is still causing severe damage to aquatic ecology and to our own health and quality of life. Beaches

are consistently closed due to bacterial contamination, drinking water contamination has caused

sickness and deaths around the region, many of our fish are poisoned with chemicals, and the sediments

at the bottom of the lakes are becoming increasingly toxic.

But the Great Lakes and waterways are showing signs of improvement. Researchers attribute the

success to the cleanup of industries that had originally sent their wastes into the river, as well as better

maintenance of sewer systems and sewage treatment plants in the Cuyahoga watershed.