AP BIOLOGY

Detailed explanation-1: -Dead zones are generally caused by significant nutrient pollution, and are primarily a problem for bays, lakes and coastal waters since they receive excess nutrients from upstream sources. Excess nitrogen and phosphorus cause an overgrowth of algae in a short period of time, also called algae blooms.

Detailed explanation-2: -Harmful algal blooms, or HABs, occur when colonies of algae-simple plants that live in the sea and freshwater-grow out of control and produce toxic or harmful effects on people, fish, shellfish, marine mammals and birds. The human illnesses caused by HABs, though rare, can be debilitating or even fatal.

Detailed explanation-3: -When there are excessive amounts of nitrogen and phosphorus in the water, algae can bloom to harmful levels. Dead zones form when the algae die, sink to the bottom, and are decomposed by bacteria-a process that strips dissolved oxygen from the surrounding water.

Detailed explanation-4: -Algal blooms are dense layers of tiny green plants that occur on the surface of lakes and other bodies of water when there is an overabundance of nutrients (primarily phosphorus) on which algae depend. This effect is called eutrophication.

Detailed explanation-5: -Algae blooms can occur when a combination of suitable environmental conditions exist for abundant algal growth (e.g., increased nutrients, warmer temperature, abundant light, and stable wind conditions).