HARMFUL ALGAL BLOOMS (HABs)

WHY IS THIS ISSUE IMPORTANT?

A small percentage of algal species cause harm to humans and the environment through toxin production or excessive growth—these are the harmful algae and they include both microalgae (microscopic, single celled organisms) and macroalgae (seaweeds). Some harmful algae produce potent toxins which cause illness or death in humans and marine organisms—fish, seabirds, manatees, sea lions, turtles, and dolphins are some commonly affected animals. Other types of harmful algae are nontoxic to humans but cause harm to fish and invertebrates by damaging or clogging their gills or by forming such large blooms that the death and subsequent decay of the algae lead to hypoxia (oxygen depletion) in the bottom waters of marine environments. Dense blooms can also block sunlight for beneficial algae and seagrasses.

HABs occur naturally, but human activities that disturb ecosystems in the form of increased nutrient loadings and pollution, food web alterations, introduced species, and water flow modifications have been linked to the increased occurrence of some HABs.