But Harold Marshall, a professor at Virginia's Old Dominion University, suggests that the species found in the Bay could be slightly different strains of those found elsewhere, and may not produce toxics. Or, he said, the Bay may not present the conditions needed for them to form dense, toxic blooms. We're not raising a warning flag here that we're inundated with toxic species. And there is ample reason for concern. In places, these blooms can cause millions of dollars in economic damage by blanketing beaches with dead fish and sending tourists somewhere else.
Some forms emit toxic aerosols as they decompose, causing respiratory problems for people downwind.
Others contaminate shellfish, and can cause symptoms from stomach illnesses to neurological disorders to death when people eat them. Yet of more than 4,000 species of phytoplankton known worldwide, only about 60 are associated with toxic effects. The story behind these blooms is complex, and scientists are working to try to unravel the intricacies. At the same time, even blooms that don't produce toxins can result in fish kills. When more algae is produced than can be consumed by predators, the excess will ultimately die and sink to the bottom and decompose in a process that can deplete the water of oxygen, sometimes killing fish, shellfish or other species in the area.