24 Oct 2011

Dolphins dying of chemical pollution off Welsh coast

Poppit Sands
A week ago I was fortunate enough to be near Cardigan in Wales for a few days - it was totally wonderful - what a great area with hills, beaches and all. It is also famous for it's bottlenose dolphins - an estimated 250 live in the area. Anyhow one day I was on Poppit Sands and ended up talking to a marine biologist working on a dead dolphin there - apparently it was his third dolphin death in Wales this year but it was too old to tell how it had died.

However I learnt that high concentrations of organochlorine compounds (particularly PCB) have been found in bottlenose dolphins in West Wales. One dolphin previously found had the highest level of PCBs recorded in this species in the UK in the last 20 years.

There are more than 200 kinds of PCBs - PCBs are basically toxic chemicals that used to be added to paints and cements, fire retardants, adhesives and hydraulic fluids. Because of their extreme toxicity, they were banned in many countries, but they still persist in the marine environment, particularly in coastal waters. They get into the fish the dolphins eat and are readily absorbed into fat, so the dolphins' blubber is an ideal reservoir. Click read more to see more but please note it includes a photo of the dead dolphin on Poppit Sands.

It seems from reading more about this that high exposure to PCBs may increase susceptibility of the bottlenose dolphins to infections. Researchers, for example, with the National Institute of Standards and Technology in Charleston, South Carolina, say that dolphin blubber carries some of the highest PCB concentrations found in any wild animal. PCBs have also been linked to fertility and reproductive issues in dolphins and can affect the immune system, exposing the dolphins to a number of serious diseases and conditions such as meningitis swelling of the brain. Scientists have also found that PCB-contaminated male dolphins don’t develop sexually while female dolphins with higher levels of PCBs have lower pregnancy rates. Often it seems first borne calves die while the second calves live - may be because the mother dolphin “burns” blubber to make milk. The PCBs and other compounds stored in the blubber become part of the milk and are transferred to the calf. The chemicals may harm the baby dolphin’s immune system, making it less able to fight off infections from viruses and bacteria.

Scientists now think that chemical pollutants such as PCBs are one of the likely causes of the decline of the local bottlenose dolphins. In talking to other folk it seems that the whole species is threatened - let us hope this is not the case.

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