Red tides are perhaps the most feared natural phenomenon to occur along coastlines, as the presence and growth of one can spell disaster for those who make their living using coastal resources. A red tide happens when a few certain species of algae bloom at an accelerated rate, resulting in a red or brown color.
The surface of the water changes color because of the rapidly accumulating algae, but the real damage doesn’t start until the algae dies and sinks to the bottom, where bacteria use tremendous amounts of oxygen to consume the dead material, choking out all other forms of life in the process. While red tides are common in many coastal regions in late summer and early autumn, these 3 red tides were some of the most significant in world history for the extent of damage they caused.
First Recorded Red Tide, 1793
The first documented red tide happened in British Columbia in June of 1793. Captain George Vancouver was navigating the central coast area. Men from his crew opened some mussels they had found in a cove and ate them for breakfast. Within minutes, they experienced numb lips and finger tips. The condition progressed until the arms and legs were paralyzed and the men were feeling dizzy and nauseated. One of the men, John Carter, died from this strange illness. It wasn’t until nearly two centuries later that the culprit was identified: the phytoplankton of the red tide had contaminated the mussels, leading to the illness of George Vancouver’s men and the death of one of his crew.
1972 New England Toxic Tide
This red tide was caused by the toxic dinoflagellate Gonyaulax. This organism is noted for its high toxicity – it produces saxitoxin and gonyautoxins. These substances accumulate in shellfish, and much like the 1793 British Columbia event, can cause paralytic poisoning and death from eating infected shellfish. This algae bloom was visible from southern Maine all the way to Massachusetts. Ever since this event, Maine has experienced outbreaks nearly every year. Massachusetts and New Hampshire have also had outbreaks, although with less frequency.
2005 New England Shellfish Disaster
The algae bloom of 2005 shut down the New England shellfish industry for so long that it cost $5 million dollars in federal disaster assistance funds. It was billed as the worst toxic tide in generations, stretching once more from Maine south to Nantucket. It was 30 miles wide in some places, and areas that had never before seen infestations became infected because of wind and currents. The toxic levels were record setting – a single serving of scallops was enough to be deadly.
Images via eutrophication&hypoxia, whoi.edu