What are HABs

Image Credits: FWC Fish and Wildlife Research Institute

In every natural body of water on Earth, tiny plant-like organisms are floating beneath the surface. These organisms are a single cell each, so small a microscope is needed to see them. These organisms are called phytoplankton. Phytoplankton use chlorophyll to collect sunlight just like land plants, but instead of making large trees, phytoplankton make lots of single cells that float around in the water. When there is plenty of sunlight and nutrients available for the phytoplankton to consume they will reproduce very quickly. High reproduction, in combination with water moving cells close together, will cause an above average amount of phytoplankton in the water; this is called a bloom or algae bloom.

Most phytoplankton species are essential to a healthy environment. They are the main food source for aquatic life, providing fish, oysters, crabs, and dolphins the energy to grow. Most phytoplankton are important for animals, but there are some species that can make animals sick or die. Of the 5,000 known species of phytoplankton, there are about 100 species known to be toxic or harmful. When these phytoplankton bloom, they can poison the water, stab other organisms with their shells, or just fill the water with too many phytoplankton. This is what we used to refer to as 'red tides', but since the bloom can be green, brown, red, or colorless, scientists changed the name to Harmful Algal Blooms (HABs).

Since scientists started to observe HABs, they appear to be occurring more often. The increased frequency of HABs is a major concern; these events can make people sick when contaminated shellfish are eaten or when people breathe toxic air sprayed from a beach with a harmful algal bloom. HAB events can result in the closure of beaches and shellfish beds, massive fish kills, death of marine mammals and seabirds, and alteration of marine habitats. This hurts commercial and recreational fishing, tourism, and valued habitats, which are important local economies and the livelihood of coastal residents.

Karenia brevis is one of the most common and well studied HABs in the Gulf of Mexico. It frequently blooms in Florida and Texas causing fish kills, contaminated shellfish, and human respiratory irritation. For more information, please watch this video or go to our Related Links page.