explain how algae blooms act as water pollution and how humans contribute to the problem.

Algal blooms act as water pollution as it cuts the oxygen supply for aquatic organisms.Humans contribute in this by dumping sewage age other organic compound rich waste.Explanation:

Algal blooms are the uncontrolled growth of algae in water these includes red tides and blue-green algae. They have very severe impacts on aquatic ecosystems, human health and the economy.

These algal blooms can be dangerous in following cases:

They produce toxins which can kill aquatic animals, peoples and other animals .They create dead zones in the water as they grow on the surface of water and cover the entire water source which resist sunlight to go beneath the water which causes the death of the aquatic plants and also the death of aquatic animals which depends on these plants.   They also effect the industries that depends on clean water.

These Harmful algal blooms can grow if they get the following requirements:

Sunlight .Slow-moving water. Nutrients (nitrogen and phosphorus) etc. This nutrients may come from the sewage and other organic wastes dumped by humans in water sources which favors the growth of these organisms.

Result: Algal bloom can take nutrients form the sewage dumped by humans in the water supply.