By Jessica Taylor/Correspondent
As any visitor to the Outer Banks can tell, it’s all about the environment. Surfing, fishing, hiking up Jockey’s Ridge to see the sunset, these treasured activities and many others wouldn’t be possible without healthy and thriving ecosystems. Sometimes it’s not always possible to see when there are problems in the environment. Environmental issues can be cryptic and hidden, such as microscopic plastics concealed in clear blue water or chemicals seeped into the ground. Luckily, we have sentinel species in the environment that give indications of poor environmental health. Bottlenose dolphins are such a species, and the Outer Banks Center for Dolphin Research (OBXCDR) has been watching, observing and monitoring bottlenose dolphins in the Roanoke Sound for the past 14 years. On the Outer Banks, we depend heavily on the sounds for our economy, recreation and enjoyment, and OBXCDR’s monitoring research clues us into the health of underwater ecosystems.
Bottlenose dolphins are great indicators of environmental health due to their long life spans, tendency to store environmental contaminants in their bodies and our ability to monitor their populations over time. Since 2008, the OBXCDR has used a research technique known as photo-identification to monitor dolphins in Roanoke Sound. We photograph the distinctive markings on the dolphin dorsal fins, catalog these photos and use these markings to track individuals over time. Long-term photo-identification studies have taught us that dolphins have long life spans, with males typically living into their 40s and females living into their 50s.
On the Outer Banks, for example, the oldest known dolphin is Onion, a male estimated to be in his early 40s. His age is based upon a sighting history of more than 30 years by photo-identification researchers in the Nags Head and Cape Lookout areas.
Dolphins also bioaccumulate chemicals in their blubber. Any microscopic pollutants in the water move up the food chain. As top predators, dolphins store these pollutants in their bodies over time. Just as with people, a heavy contaminant load may be visible to us by the dolphins becoming sick. In an even sadder situation, female dolphins may metabolize these chemicals in their blubber and the chemicals may enter the milk that goes to the calves. In fact, in some areas with critically poor water quality, the first born calf of a female has a low chance of survival due to these chemicals.
The presence of chemicals in the marine environment may also cause skin lesions on the dolphins. As they come up to the surface to breathe, not only their dorsal fins are visible but any lesions or diseases on their skin are visible as well. Six different types of lesions have been seen on dolphins in the Outer Banks, but some may just be reactions to low water temperature or freshwater. Some lesions indicate disease, but in certain cases point to the presence of environmental contaminants.
Perhaps most tellingly, dolphins’ presence or absence from an area tell us about the habitat’s environmental health. Absence in an area where they’re usually seen could indicate problems lower down the food chain. Another type of pollution in the marine environment is noise pollution. It is invisible to us but may have a large impact on dolphins, fish, and other organisms that depend upon sound. Loud sounds underwater are known to disrupt dolphins and fish, making some habitats unsuitable. If these organisms leave the area, it changes the ecosystem and, potentially, its economic value as well.
OBXCDR’s monitoring data of the dolphins in Roanoke Sound suggests that the population has been relatively stable, which is a good sign for the health of the sound and our local environment. Each year, we add new dolphins to our catalog, observe known females with new calves and reacquaint ourselves with the seasonal resident dolphins who return year after year. Even though the Outer Banks has changed over the years since we began our research study, the passion and concern for our environment that locals and visitors share has remained the same. And with the dedication to keep our local environment healthy, along with a little help from the dolphins, the treasured activities that we enjoy on the Outer Banks can continue for generations.