Answer:
Different types of macro organisms live in different qualities of water. This is because some are more resistant to pollution than others. For example, leeches and aquatic worms thrive in polluted water. Others are very sensetive to it, such as Mayflies, Caddisflies and Stoneflies.
To prevent water pollutions, you can be careful about what goes down your drains. All water from your drain has to re-enter the ecosystem at some point. Pouring oil, fat or grease down the sink is a very bad thing for the environment.
Water is important because we need a healthy water supply to keep our communities healthy. If our water supply such as a river or lake is contaminated with pollutants, it will become undrinkable.