Algal Bloom

A rapid increase in the population of algae in an aquatic system, e.g. as a result of an excess of nutrients (particularly phosphorus and nitrogen). As more algae and plants grow, others die. This dead organic matter becomes food for bacteria that decompose it. With more food available, the bacteria increase in number and use up the dissolved oxygen in the water. When the dissolved oxygen content decreases, many fish and aquatic insects cannot survive.