FloridaRed Tide

Just published in the journal, Aquatic Toxicology, is a study by Dong-Ha Nam and colleagues on the effects of brevetoxins on sharks. Brevetoxins are the toxins that are released by organisms like Karenia Brevis, the organism that is behind Florida Red Tide. The conclusion? Brevetoxins modify the neurochemistry of shark brains, making them over-excited and even killing them.

The authors of this study focused on lemon sharks entirely, they believe however that this research applies to all sharks.

Here’s how the study went:

30 Lemon sharks were captured from the Gulf of Mexico over a period of 3 years.  These captures occured during period of red tide blooms and during periods without red tide blooms.  One of the sharks collected had already been killed by red tide.

he authors assayed for the levels of brevetoxins in the tissues, neurochemical enzyme activity, as well as neurochemical receptor binding. They found high levels of brevetoxins in the liver, gills and brains of sharks that had been exposed to red tides. They also found significant changes in neurochemical enzymes and receptors that were strongly correlated to elevated levels of brevetoxins in the brains.

According to the authors, the brevetoxin is capable of easily crossing the blood-brain barrier (that protects the brain) and binding very strongly to a protein that controls sodium flow in the brain.  This disruption of the sodium flow causes the nerve cells to overfire, leading to hyperexcitability and ultimately, death.

Sorry I can’t link to an online source as this science journal is  a little old fashioned (weird) and doesn’t have a web site.  However if you want more details you can go out and buy a copy of the journal v 99, somewhere, I can’t find where they even sell the print copy online.