Scientists fear pollution is behind the spread of skin lesions in dolphins
Marine biologists studying bottlenose dolphins (Tursiops truncatus) off the central California coast fear ocean pollution could be lowering the dolphins' immune system responses, threatening the future of the population.
The scientists have identified five different skin condition categories.
Between 2006 and 2008 the scientists1 monitoring bottlenose dolphins in Monterey Bay discovered the dolphins were suffering from five different skin conditions, including "pox-like" lesions and discoloration. The conditions were assessed only by their appearance and a definite diagnosis is not currently available, but the research team is nonetheless concerned by the widespread nature of these conditions in the dolphin population. Eighty-eight coastal surveys were carried out by Earthwatch scientist Dr. Daniela Maldini2 and her colleagues with the help of teams of volunteers from Earthwatch.
Coastal dolphins were encountered in all of the surveys, which took place between August and October each year, and 212 adult bottlenose dolphins and 42 calves were individually identified. Of these, 133 adults and 30 calves were affected by one or more skin conditions. Pox-like lesions were the most prevalent skin condition, affecting 80 per cent of the population. According to the scientists, this matter now needs urgent investigation to determine the causes of the conditions.3 In the light of the findings, Dr. Maldini is concerned for the long-term health of the population of bottlenose dolphins in coastal California, and the effects of exposure to pollutants which may lower immune systems and the ability to fight diseases.
"Our first suspicion immediately falls on contaminants such as pesticides, heavy metals, organochlorines (organic compounds containing carbon and hydrogen) and fire retardants which have been shown to affect the immune system in other species. If we can find a link we will have a smoking gun to address this problem. The effects of these skin conditions on the population should not be overlooked, especially because the overall coastal California bottlenose dolphin stock is currently estimated at less than 500 animals."
"The oceans are sick. Toxic substances are now reaching the marine environment in larger and larger quantities and the long term effects of these substances are unknown. Dolphins are at the top of the food chain and they are mammals like ourselves. They are a perfect ambassador to teach the public about these issues."
The marine biologists have also discovered previously unseen skin lesions in two dolphin calves.
Executive Vice President of Earthwatch, Nigel Winser, said: "The results from this research are yet another wake-up call to the world about the relentless damage which is being done to the oceans. Dolphins are a ‘canary in the coal mine' for the oceans and it's clear that more focused research is needed into the causes of these skin conditions."
Reduced water quality due to pollution is a big issue in coastal waters. Chemical contamination is affecting the entire food chain including species consumed by humans and dolphins alike. Dr. Maldini has joined forces with Dr. Thomas Jefferson of Clymene Enterprises and with Dr. Ted Davis at Teknova to investigate the causes of the skin conditions. The priority is to identify the infectious agents and their occurrence in the environment and to monitor individual animals' health. Funding will be critical to ensure the success of this endeavor.
During their research, the marine biologists also discovered previously unseen skin lesions in two bottlenose dolphin calves in Monterey Bay. They are using these two case studies to spread the word among the scientific community that something may be amiss with the population and are monitoring these and other calves.
Monterey Bay is located along the central California coastline and the bay is within the Monterey Bay National Marine Sanctuary. It is California's second largest bay. Its nutrient-rich and deep waters support extensive fish, invertebrate, seabird and marine mammal populations.
1 Prevalence of Epidermal Conditions in California Coastal Bottlenose Dolphins (Tursiops truncatus) in Monterey Bay (Daniela Maldini, Jessica Riggin, Arianna Cecchetti, Mark P. Cotter) was published by the Royal Swedish Academy of Sciences in June 2010.
2 Dr. Daniela Maldini is the President and Chief Scientist of Okeanis, a central California-based non-profit organization dedicated to the study of marine mammals and their role in the marine environment. She is also adjunct faculty at Gavilan College in Gilroy California.
3 A family of viruses known as the Poxviridae family is responsible for a wide range of pox diseases both in humans and other animals. Little is known about marine pox viruses, but at least two different types of pox viruses have been isolated in dolphins. Research on these viruses in dolphins is still in its infancy.