Why “red tide” dinoflagellates make compounds that are toxic to fish and humans has been a mystery for decades. Possible functions include aiding prey capture, deterring grazers, or neutralizing competitors. NCCOS-sponsored scientists at Texas A&M University studyingKarenia brevis, the dinoflagellate responsible for “red tides” in the Gulf of Mexico, have an explanation.
In the June 13 2011, online Early Edition of the Proceedings of the National Academy of Sciences, graduate student Reagan M. Errera and Professor Lisa Campbell, at Texas A&M University, have identified a trigger for production of brevetoxin, the potent neurotoxin found inKarenia brevis. They suggest as ‘red tides’ move onshore and mix with fresher water, theKareniacells adjust rapidly to the lesser salinity by dramatically increasing the brevetoxin concentration in their cells.
These findings provide a reason for brevetoxin production – long a critical gap in knowledge forK. brevis. It also means that maximum toxicity will be near shore where human impacts will be greatest. The toxins are released when waves break at beaches during red tides, causing respiratory problems for tourists and residents near beaches. Further, the toxins are taken up by near shore shellfish, making the shellfish so toxic to humans that commercial and recreational harvesting must be banned.
This research is conducted under the auspices of the National Centers for Coastal Ocean Science.