What do the terms algal bloom & red tides signify?

An algal bloom or marine bloom or water bloom is a rapid increase in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Algal bloom concentrations may reach millions of cells per milliliter. Colors observed are green, yellowish-brown, or red. Bright green blooms may also occur. These are a result of blue-green algae, which are actually bacteria (cyanobacteria). Some algal blooms are the result of an excess of nutrients (particularly phosphorus and nitrogen) into waters and higher concentrations of these nutrients in water cause increased growth of algae and green plants. 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. This results in a dead area. Red tides are conditions when a dinoflagellate population increases to huge numbers. This â??bloomâ?? may be caused by nutrient and hydrographic conditions, although the environmental conditions which result in red tides are not completely understood. The water is discolored red or brown due to the presence of dinoflagellate cells numbering up to 20 million cells per liter. Red tides are composed primarily of one species of dinoflagellate which has been rapidly growing. read less