Red tides and wildlife

Posted by Dawn M. Smith Feb 14, 2007

Red tides, now more properly called Harmful Algal Blooms (HABs) as they come in many colors, are implicated in many marine animal deaths. These HABs are responsible for human illness, and occasionally death, as well.

Fish and invertebrates eat algae. Most of the time that’s not a problem. It becomes a problem when the HABs appear. They are called harmful because they contain toxins. Most people are familiar with Paralytic Shellfish Poisoning, one of the common types of HABs. The toxin is released when the fish or invertebrates are eaten by humans, birds or marine mammals.

The Mediterranean monk seal loss of 2/3 of its largest colony was a direct consequence of an HAB. Rockhopper penguin declines have also been linked to HABs. Dolphin mortality events on the eastern US coast in recent years have coincided with HABs. Marine mammals and seabirds, including the brown pelican, in the eastern Pacific suffer from domoic acid poisoning, a by-product of one type of algal bloom which causes liver damage and is often fatal. While most of these animals face multiple challenges, the HABs can be the straw that breaks the camel’s back.

But these HABs are natural, so why should we be concerned? Because nitrogenous waste from agricultural fertilization or sewage outfalls has been linked to increasing HAB occurrences. These nitrogenous wastes provide food for the algae. And, unfortunately, it seems that some species of algae prefer this human produced form of nitrogen over natural sources. As more and more of us spend more time near the coast, the problem will only get worse. Unless we clean up our act.