Boat noise in Bocas "potentially harmful" to dolphins: researchers

April 14, 2014

Panama’s once-sleepy Bocas del Toro Archipelago is an increasingly popular destination for tourists. Attractions include dolphin-watching tours around the mangrove cays of the Caribbean getaway. While the dolphin population of Bocas is relatively small — about 200

individuals — a boat tour can almost guarantee a close encounter with the charismatic creatures. Not surprisingly, dolphin-watching boat traffic has increased exponentially in recent years.

New research by visiting scientists at STRI’s Bocas del Toro Research Station shows that noise from boat motors alters the way bottlenose dolphins communicate while foraging, one of their most noise-sensitive activities. Dolphin whistles become lower in minimum -ending- and peak frequencies, but longer in duration. Lower and longer whistles can travel longer distances allowing dolphins to avoid or reduce their signals to be masked by boat engine noise. However, this also means that dolphin acoustic communication space is drastically reduced by the roar of boat motors prompting them to make these changes.

The findings, published in the Journal of the Acoustical Society of America in April, “clearly suggest that interactions with dolphin-watching boats are potentially harmful.” Authors Laura May-Collado, of the University of Vermont, and Shakira Quiñones-Lebrón, of the University of Puerto Rico, wrote: “Our results also indicate that intrusive dolphin-watching activities and associated engine noise may be negatively impacting individual fitness in this small dolphin population.”

Between 2004 and 2012, May-Collado and team collected 56 hours of dolphin whistle recordings from 47 individuals, all photo-identified. The recordings were made in the presence of two to 17 dolphin-watching boats, with an hourly turnover of 34 boats. These are low-season figures. During the peak of the tourist season, up to 100 boats can interact with dolphins in a single day.

Aggressive dolphin watching can have other negative effects. “Dolphins reduce their feeding and socializing time, two very important activities for their survival, when the number of boats increases,” said May-Collado. Her team has also documented boat strikes, which killed at least 10 dolphins between 2012 and 2013. They also observed calves separated from their mothers, which can reduce the chances of survival of offspring. “All in all, this is an industry that is far from being sustainable in Bocas. So we are trying to increase education, training, and outreach activities and use the information we have to propose a management plan that minimizes risk of population extinction in Bocas.”

 http://www.stri.si.edu/english/about_stri/headline_news/news/article.php?id=1795

Coral Reefs in Panama • Are they still pristine?

Aaron O'Dea's time machine is a 20-foot aluminum tube. Beneath the waters of Panama's western Caribbean, he drives it into the rubbly seabed with a 45-pound cylindrical hammer.The strenuous effort quickly depletes oxygen tanks and leaves Aaron and his team aching and breathless.

 

Although the dive site seems pristine, the scenery is deceiving. Surrounded by warm, emerald waters and untouched mangrove islets, Panama's Bocas del Toro - like most coasts of the Caribbean - abounds in natural beauty. But beneath the surface, the seabed once blanketed in vibrant reef communities is now covered with grayish dead coral.
Like a detective on a cold case, Aaron O'Dea, a paleobiologist at the Smithsonian Tropical Research Institute (STRI), drills down hundreds of years into the seabed in search of clues to present day changes in marine ecosystems of the Caribbean.
Coral fossils are emissaries of the ocean's past. Highly sensitive to environmental changes, they serve as indicators of ocean health. Though warming seas, acidification, pollution and overfishing are generally held responsible for the decline of coral reef communities, precisely when and why their deterioration began is unknown.
"The health of the oceans is like a patient with a complex medical history who falls ill in a foreign country. If local doctors treating the patient don't have a full medical history, they may endanger the patient's life," says O'Dea who sees how baseline data will aid marine conservation efforts. "If we wish to diagnose and treat life in the seas, it is essential we know the ocean's history."

With each hammer strike, the coring system delves into the past collecting sediments and fossils. Aaron's team journeys 50 years back in time just prior to the precipitous decline of the reefs. One hundred years ago reveals the impact of Bocas del Toro's first intensive banana plantations. Five hundred years into the past corresponds to the arrival of Europeans to this 9,000 year-old archipelago that is now an international tourist destination.

"The question is, what did the Caribbean look like in the past and what were the principal drivers of the changes we see today," says O'Dea. The fossils will tell the story.
Core samples with marine sediments layered one on top of the other will be sent to Scripps Institution of Oceanography where x-ray scans will determine the types of sediment retrieved. Shellfish fossils will be dated with uranium-thorium, revealing their dates to within a handful of years. Back in Panama, O'Dea's team of lab assistants and students will spend months interpreting the fossilized mollusks, coral, clams and more; cleaning and classifying them according to age to reconstruct the marine history of Bocas del Toro.
"Once we demonstrate our aim in Bocas del Toro, we'll expand both spatially and temporally throughout the Caribbean and the rest of the world. Our findings will be used to direct the recovery of the seas."

Aaron O'Dea's coring system consists of a 6-meter (20-foot) aluminum tube marked off into 20-centimeter (8-inch) sections. These visual references help his team monitor how far the cylinder has entered the seabed.

 http://www.stri.si.edu/sites/what_is_pristine/index.html