Ocean circulation could be responsible for the severity of the 2018 red tide

The harmful algae that cause the red tide are currently at almost undetectable levels in Florida waters compared to much higher concentrations at the same time last year. Red tide algae, Karenia Brevis, causes respiratory problems, is responsible for the massive mortality of fish and is often blamed for damaging tourism.

Although traces of the proliferation are still present off the Gulf of Mexico, a new study published in the Journal of Geophysical Research-Oceans finds that ocean circulation has made 2018 the worst year of the red tide in more than a decade.

By affecting nutrient levels off the coast, scientists at the University of South Florida (USF) have shown that ocean circulation plays a key role. If offshore nutrient levels are high in the spring due to the rise of deeper oceanic waters, there are no large blooms of red tides along the coastline. autumn. Such a rise in water did not occur in the winter and spring of 2018, thus allowing the formation of a new proliferation offshore in the spring and summer of 2018. A circulation of The lift was then installed towards the end of July, ensuring that the new proliferation would be transported to the coast along the coastline. the bottom where it reinforced what was already in place since 2017.

Tropical storm Gordon temporarily disrupted the upward circulation, allowing some of the new bloom to be washed away in the Florida Panhandle. After Gordon's passage, the ascending circulation then allowed the bloom to be transported off to the surface to eventually be transported to the east coast of Florida by the Gulf Stream. So, the rare occurrence of Karenia Brevis at three different locations (West Florida, Panhandle and East Coast) can be attributed to ocean circulation.