Freshwater Ecosystems 2

A Vital Resource

Canada contains about 7% of the world’s freshwater supply, having the world’s greatest number of lakes, compared with 8% for the United States. However, with the greater population in the United States, their need is much greater and efforts have been made to divert water from the Great Lakes further south to Nevada. The Canadian government has put into force legislation to stop the diversion, but pressure will continue to mount as American water sources continue to be depleted. In fact, California has resorted to treated sewage water as a source of drinking water.

A recent article in the Sierra Vista, Arizona newspaper The Herald refers to the dilemma, and quotes the United Nations’ prediction that "water will be the oil of the 21st century. Wars will be fought over water". The article goes on to point out that it takes 37 gallons of water to make one cup of coffee, 17 gallons to make one can of soda and 713 gallons to make one cotton shirt. That’s a total of 770 gallons of water and you haven’t even watered the lawn!

Water is wasted by inefficient watering, leaking irrigation systems and inappropriate plants. Each one of us can help by doing some very simple things. Turn the water off while brushing our teeth, shaving, doing dishes, etc. Choose outdoor plants that do not require a lot of watering.

Animal Adaptations

Many plants and animals have adapted to the freshwater biome and could not survive in water having a higher salt concentration. As this ecosystem covers a vast portion of the world, the animal life found can vary considerably.

Breathing in Water - Fish are able to obtain oxygen through their gills. Fish such as trout have adapted to living in rivers and streams where the water is cooler, clearer and has a higher oxygen level. At the mouth of these water sources, the sediments create a more murky environment with lower oxygen levels and fish such as catfish and carp have adapted to exist in these areas.

There are three zones in lakes and ponds: littoral zone (the topmost and warmest is home to snails, clams, insects, crustaceans, fishes and amphibians and the eggs and larvae of dragonflies and midges). These resources provide food for turtles, snakes and ducks. The limnetic zone is close to the surface and consequently receives a good deal of light. This zone contains a variety of freshwater fish. The profundal zone is very dense and cold, with little light penetrating this region. Only heterotrophs (animals that eat dead organisms) are found in this region

Swimming & Diving - Mammals (badgers, otters, mink) live near water and are capable of swimming to catch their main food source, fish. Amphibians and reptiles (toads, frogs, alligators, crocodiles, salamanders and newts start life underwater as eggs and tadpoles, and then move to ground as adults. Insects such as skaters, water beetles, mosquitoes and dragonflies can skim over the surface of ponds, playing a critical role in the food supply for other animals. Some spiders can actually take a bubble of air with them underwater.

Specialized Diets - Many species of ducks, geese and swans also call the freshwater biome their home, feeding on a number of different items including fish, while wading birds such as herons and egrets wander through the mud shallows searching for insects.

Temperature - Manatees have adapted to survive in warm water and migrate south. Some have found the warm water near power plants, and consequently do not have to migrate.

Teeth - Beavers shape their environment more than most other animal species on Earth, utilizing their ever-growing teeth to cut down trees and plants to create dams to create their dens. Their actions are not always appreciated by nearby humans, but they are vital to the ecology, causing a build-up of water which in turn creates a new wetland. Beavers also help to purify water because the sediments and any toxins are trapped behind the dam.

Page 3> Freshwater Ecosystems