Bottlenose dolphins in the English Channel are being polluted with dangerous levels of toxic chemicals from pesticides and industrial waste, a study has warned.
The chemicals, which include chlorine and the heavy metal mercury, are building up in the blubber and skin of one of the largest coastal dolphin populations in Europe.
Concentrations of mercury found in skin biopsies of 82 wild dolphins in the Channel are among the highest recorded.
The chemicals work their way up to the top of the food chain and has a disastrous impact on an animal’s fertility and immune system.
Bottlenose dolphins in the English Channel are being polluted with dangerous levels of toxic chemicals caused by pesticides and industrial waste, a study has warned
Toxic organic pollutants can be detected even in the deepest dwelling marine life and most, particularly those containing chlorine, were outlawed from developed countries in the 1970s and 1980s.
‘These organic compounds are able to dissolve in fats and oils, and consist of the by-products of various industrial processes and pesticides, among others,’ said Dr Krishna Das, a zoologist at the University of Liege, Belgium.
‘Bottlenose dolphins are often used to study levels of environmental pollutants, as the organic compounds accumulate within their thick layer of fatty tissue.’
The chemicals known as PCBs (polychlorinated biphenyls) pose a serious threat to wildlife and humans.
They were used as a refrigerant because they’re difficult to burn, and have been banned for 40 years.
But they are extremely durable and remain in ecosystems even four decades after being outlawed.
Recent research has suggested the long-lasting man-made pollutant could lead to the disappearance of half of the world’s killer whales in the next 30 years.
So Dr Das and colleagues assessed levels of PCBs and mercury in the skin of free-ranging bottlenose dolphins inhabiting the Normanno-Breton Gulf in the English Channel.
The study, published in the journal Scientific Reports, found large amounts in the blubber of the loveable sea creatures.
The chemicals – some of which were banned 40 years ago – are building in the blubber and skin of one of the largest coastal populations in Europe
They were predominantly made up of chlorine-containing compounds from industrial fluids – comprising more than 91 percent of the organic chemicals in their skin.
What’s more, levels of mercury in skin samples were similar to those previously described for bottlenose dolphins in the Mediterranean Sea and Florida Everglades – areas notorious for contamination.
The pollutants weaken their immune system. They face higher rates of illness and disease than captive counterparts.
In humans, this kind of chronic immune response has been linked to cancer, heart disease and increased vulnerability to infectious disease.
Dr Das said: ‘The bottlenose dolphin is a relevant species for examining environmental contamination trends in coastal areas.
‘The species is widely distributed in estuarine and nearshore waters, is a long-lived species high in the marine food web and a thick layer of blubber in which pollutants accumulate.’
She said previous risk assessment investigations on the potential effect of PCB exposure suggested they were likely to harm survival of calves – and reduced population growth.
About 420 coastal bottlenose dolphins live in the the Normanno-Breton Gulf around the Channel islands.
About 420 coastal bottlenose dolphins live in the the Normanno-Breton Gulf around the Channel islands
Dr Das said: ‘The reported concentrations are among the highest reported for cetaceans.
‘We strongly recommend the Normanno-Breton Gulf be a special area of conservation candidate because it contains the last large European population of bottlenose dolphins.’
Dr Das added: ‘The bottlenose dolphins in European waters are protected by the Habitats Directive.
‘Their conservation requires the creation of special areas of conservation and the need for strict protection.
‘Despite this European directive, human activities are increasing in the Normanno-Breton Gulf.
‘The potential threats include pollutants, noise pollution, particularly construction noise, disturbance by tourism activities and by-catch.
A recent study of bottlenose doplhins in US waters identified emerging infectious diseases, tumours, antibiotic resistant bacteria and alarmingly high levels of contaminants
‘Bottlenose dolphins have declined in the northeast Atlantic. The historic stranding data in Europe suggest coastal bottlenose dolphins became locally extinct or depleted in the late 1960s to the mid-1970s, including those in the UK and the Dutch coast.
‘The last member of a resident bottlenose dolphin population in Arcachon, France, died in 2001, and the small resident bottlenose dolphins group in Portuga declined over several decades due to low calf survival over several decades.’
A recent study of bottlenose dolphins in US waters identified emerging infectious diseases, tumours, antibiotic resistant bacteria and alarmingly high levels of contaminants.
As large predators near the top of the food chain, dolphins accumulate any toxins ingested by their prey.
