Harmful algal bloom

A harmful algal bloom (HAB) can refer to a dense aggregation of phytoplankton, algae or cyanobacteria in a marine or aquatic environment, such that it causes negative impacts to other organisms via biotoxins, mechanical damage or other means. The term "red tide" is often used to describe these phenomena, however scientists now prefer the term HAB, since HABs are often associated with large-scale marine mortality events and have been associated with various types of shellfish poisonings.
 * 1) not all algal blooms are harmful,
 * 2) not all algal blooms cause discoloration of water, and
 * 3) these blooms are not associated with tides.