Did you know that red tides affect dolphins? Red tide is a higher-than-normal concentration of a naturally occurring, microscopic algae called Karenia brevis, often abbreviated as K. brevis. It produces brevetoxins — powerful and potent neurotoxins — that can kill marine animals and be harmful to humans, especially people with chronic lung conditions.
The Sarasota Dolphin Research Program was among the first dolphin research groups to establish a long-term prey monitoring program to track changes in prey abundance and diversity in relation to dolphins. As a result, we were the first to quantitatively document changes to an estuarine fish community from a severe red tide harmful algal bloom, including dramatic (greater than 90 percent for some dolphin prey species) declines in fish abundance, changes in size classes, species diversity and community structure, recovery times and the apparent responses by resident dolphins to changes in prey availability. We found that following a severe red tide in 2005-06, Sarasota Bay dolphins altered their ranging and social patterns and began interacting with anglers with increasing frequency, with increased mortality from ingestion of fishing gear while trying to take bait or catch from lines. In 2006, 2 percent of the members of the resident dolphin community died from interactions with recreational fishing gear.
As part of our prey monitoring work, we collect twice-monthly water samples from 10 fixed stations throughout Sarasota Bay so they can be tested for Karenia brevis,. We also collect samples from another 30 winter and 40 summer purse-seining sites in Sarasota Bay, which helps us correlate fish abundance with red tide cell counts. The cell counts that we gather help support a joint red tide monitoring program conducted by Florida’s Fish & Wildlife Conservation Commission and Mote Marine Laboratory.
Here are some of our scientific publications related to red tides and dolphins: