Field Notes
U.S. Fish & Wildlife Service
Field Notes Entry   
Matagorda Island Hit By Red Tide
Southwest Region, October 2, 2006
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In early October, Matagorda Island’s gulf beach was hit by a red tide. This tide stretched from Cedar Bayou 18 miles north.  Red tides are the result of massive algal blooms; in this case the algae involved was Karenia brevis.  K. brevis produces several types of toxins such as brevetoxin which can become an airborne vector causing breathing difficulty in humans.  K. brevis also produces toxins that can accumulate in the digestive tract of filter feeders which can then be transferred to marine mammals, birds, and humans.  

Red tides are a naturally occurring event, however there is some evidence that the frequency and intensity of red tides is increasing as a result of pollution and increasing ocean temperature.    

The most obvious impact of the red tide on Matagorda Island was a major fish kill.  To collect information on the scale and species involved in the kill, three 250 meter transects were surveyed on the beach.  Within each transect species composition, size, and total number of fish were counted.

Contact Info: Martin Valdez, 505-248-6599, martin_valdez@fws.gov
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