In a paper published in the June 13, 2011, online early edition of the Proceedings of the National Academy of Sciences (PNAS), graduate student Reagan M. Errera and oceanography professor Lisa Campbell in the College of Geosciences have identified a trigger for production of brevetoxin, the potent neurotoxin found in Karenia brevis.
Graduate student Regan Errera and Oceangraphy professor Lisa Campbell.They suggest that as red tides move onshore and mix with fresher water, the Karenia cells must adjust rapidly to the change in salinity. As they adjust, brevetoxin within the cell increases to allow cells to keep their water and salt content in balance more efficiently.
Until now, a functional role for the diverse collection of toxins produced by dinoflagellates was a mystery. Scientists have suggested that possible functions include aiding prey capture, deterring grazers, or inhibiting growth of neighboring algae.
Graduate student Regan Errera and oceanography professor Lisa Campbell
"The connection between salinity conditions and an increase in toxin production in K. brevis cells provides the simplest explanation," says Errera, a recent recipient of a graduate fellowship for excellence in research and teaching at Texas A&M.
Micrograph of K. brevis, a microscopic algaeIn their PNAS report, Errera and Campbell demonstrate that brevetoxin production increases dramatically when cells are shifted from higher concentrations of salt typical of the open ocean to lower salinity typical of coastal waters. In fact, the transition to lower salt environment triggered a 14-fold increase in brevetoxin, they say. In addition, the findings indicate a significant increase in an additional compound called brevenal, already being studied to treat cystic fibrosis.
Red tides, or harmful algal blooms as they are more correctly known, have far-reaching ramifications on human and ecosystem health, as well as a significant influence on the local economies of bloom prone areas, the Texas A&M researchers note. Karenia brevis blooms directly affect human health. Eating shellfish contaminated by accumulated brevetoxins causes neurotoxic shellfish poisoning, and aerosolized brevetoxins in sea spray can cause reduced respiratory function, they explain.
Red tides can harm ocean life and affect human health (Credit: Texas Parks and Wildlife Department)"Now that we have a plausible explanation for why Karenia brevis produces toxins, it will help coastal managers, public health officials, and others prepare for and respond to the impacts," said Quay Dortch, the program manager of the NOAA program that funded the research. "We now understand that maximum toxicity will occur in the zone near the coast where shellfish are harvested and where people are exposed to toxic aerosols, especially when near-shore salinities are low."
This research was supported by the National Oceanographic and Atmospheric Administration's Ecology and Oceanography of Harmful Algal Blooms program.
Contact: Lisa Campbell at 979.845.5706 or Karen Riedel at 979.845.0910 or