Nearly one in every three bottlenose dolphins in the Indian River Lagoon has a skin condition that includes discoloration and white growths resembling cauliflower or barnacles. For some dolphins, the growths appear to be fatal according to biologists at Harbor Branch Oceanographic Institution in Ft. Pierce. Since the protected mammals are at the top of the food chain, dolphins are considered a good indicator of the lagoonís health. But their health may also have implications for humans, since we share some of the same diseases, says Stephen McCulloch, director of dolphin research at Harbor Branch. The skin conditions have been characterized by mild discoloration and polyps that ultimately develop into worse lesions that can cover much of the dolphinsí back. McCulloch said itís too early to say what is causing the skin conditions and that more research is needed.But it may be linked to increasing pollution along the lagoon from population growth.
There are estimated to be between 500 and 800 bottlenose dolphins in the lagoon region. About 500 have been photographed and 400 identified by their distinguishing marks. "Approximately 30 percent of them show signs that are suggestive of some type of unusual skin disorders of varying degrees," McCulloch said. Scientists at Harbor Branch first started noticing more skin problems on the dolphins about three years ago, while embarking on a five year study of the mammalís population. Researchers have also witnessed an increase in other threats to dolphins, such as hepatitis, meningitis, cancer, bacterial legions that cause heart murmurs, and fungal skin disorders.
Scientists donít know yet whether a surge of dolphin deaths last year and the skin conditions are linked. Last summer 29 bottlenose dolphins were found dead in the Indian River Lagoon. Most of these were found in a small area between the 520 causeway and the Melbourne Causeway. The higher than average number caused concern among biologists at Hubbs-Sea World Research Institute, the primary stranding response team in the lagoon. Adding to the concern, was the discovery that several dolphins were severely emaciated and that there were fish kills reported in the general area in May and June. The National Marine Fisheries Service declared the die-off an Unusual Mortality Event, which has led to an investigation by multiple agencies. Many of the dolphins were severely decomposed preventing in-depth sample analysis. A few fresh carcasses were found and tissue analyses are still underway. While the ultimate cause of the die-off may never be known, some sample analyses have provided data that exclude common infectious disease and red-tide as probable causes.