Is algae good or bad in a stream or river?

Question

i have seen an increase in algae in a stream in front of my house

Answer 1

That increase of algae is due to increasing amounts of detergent, that is food for algae.

Men has copyed nature in making slow sand filters, it´s one of best ways to make raw water become potable. The active part of those filters is algae., it removes odors, taste, bacteria and most virus. That is how nature purifies water in rivers.

http://en.wikipedia.org/wiki/Slow_sand_f...

Answer 2

Algae are present in creeks, rivers and wetlands at all times. However, when the environmental conditions for the algae become optimal, the algae grows rapidly and blooms form on the water's surface. Freshwater algal blooms range in colour from dark green, to yellow, or blue-green in colour and look like scum on the surface of the water.

Algal blooms are believed to be caused by three main factors:

stagnant or slow flowing water

high levels of nutrients, and

the weather being sunny and hot for long periods.

Algal blooms have many impacts on the ecosystem.

In the fresh water environment, algal blooms can cause the following threats:

To recreation and tourism - Algal blooms often lead to the closure of local waterways for swimming, fishing and boating. They can cause major fish deaths and reduce the agricultural and tourism of the affected area. It has been estimated that algal blooms cost Australia $150 million a year.

To human and livestock health - Toxins produced by the algae make drinking water dangerous for humans and animals. They can also cause unpleasant odours and tastes in the water that make recreational activities such as swimming, boating or fishing impossible. Water that becomes affected by a bloom is also unsuitable for agricultural use.

To water supply - When blooms form in drinking water storages, such as reservoirs or dams, they can cause serious problems for drinking water suppliers. Some species of blue-green algae produce chemicals that cause musty or earthy tastes and odours in the drinking water. Removing these chemicals requires extensive treatment and, in severe cases, the water becomes undrinkable. Other species of blue-green algae can also produce toxins that are very dangerous to humans and animals if they are consumed, inhaled or even touch the skin.

Answer 3

indicates prescence  of  pollutants  in  the  water