Reasons for Toxic Algae

Leave a bucket of water standing for a few days, and you will see something green appear on the inside surfaces. That green stuff is made of algae. "Algae" is the plural form of the word "alga." Alga is a one-celled organism that lives in water and reproduces very quickly when the conditions are right. Like all organisms, algae produce waste material. Some algae produce waste that is toxic.

Saltwater and Fresh Water

• There are two forms of algae that are sources of great concern now, one that lives in fresh water and the other that lives in saltwater. The freshwater organism is named Cyanobacteria, but more commonly known as blue-green algae. Blue-green algae was what eventually made most of the petroleum now buried in the earth. The salt water variety of greatest concern is Pseudo-nizschia. Cyanobacteria becomes problematic with reproduction explosions -- called blooms, and blooms are caused by increased levels of nitrogen. Pseudo-nitzschia becomes problematic with changes in the mineral composition of the water.

Cyanobacteria

• Blue-green algae are distributed worldwide, and prefer slow moving or still water. They proliferate more rapidly with sunlight and a supply of nitrogen. They are normally kept in balance by the nitrogen absorption of other aquatic plants, but with a sudden surfeit of nitrogen, they bloom. The toxins that Cyanobacteria produces include liver toxins, nerve toxins and toxic alkaloids that cause severe digestive tract problems.

Pseudo-nitzschia

• Pseudo-nitzschia is a salt water alga that uses nitrogen to reproduce, though nitrogen enrichment alone is not the cause of the production of toxins. Though the dynamics of Pseudo-nitzschia toxicity is not yet well-understood, there is strong evidence that production of domoic acid -- a nerve toxin -- is associated with relative drops in the levels of silicate, phosphate or iron. Simply killing the Pseudo-nitzschia is not an option, because it forms an essential part of the oceanic food web. Domoic toxicity is correlated to higher nutrient levels (human, animal and vegetable wastes), though the mechanisms of causation are still not known.

Aquatic Life Effects

• Both Pseudo-nitzschia and Cyanobacteria have profound effects on aquatic life as well as affecting human and land animals. Cyanobacteria poisons some fish, and its rapid die-off subsequent to a bloom leads to decomposition which deoxygenates the water, causing fish to die en masse from hypoxia. Likewise, Pseudo-nitzschia poisons some sea life, and deposits in others -- like shellfish -- which then poisons anything that eats the shellfish. Pseudo-nitzschia blooms can also lead to eutrophication, or de-oxygenation of the water.