A recent study of the effects of pollution on the bottlenose dolphin population in the Shannon estuary has shown that levels are "elevated" but lower than results reported from the Mediterranean.
Organochlorine levels derived from pesticides and other pollutants in the dolphins surveyed will not compromise their health, Dr Simon Berrow, co-ordinator of the study, says.
Levels of persistent pollutants are higher in the Shannon mouth's bottlenose dolphins than in harbour porpoises and common dolphins sampled outside the estuary, he says. However, the levels are similar to white-sided dolphins which mass-stranded in Co Mayo and to bottlenose dolphins sampled in Scotland.
The Shannon estuary is the site of the only known resident group of bottlenose in Ireland and has been designated a candidate Special Area of Conservation (SAC) under the EU Habitats Directive, the only protected marine habitat for dolphins or porpoises in Ireland.
As part of a long-term programme to identify the main threats to the health and status of the dolphin in the estuary, a study was carried out by the Shannon Dolphin and Wildlife Foundation.
Persistent pollutants are "ubiquitous" in the marine environment, Dr Berrow explains, and dolphins may "bio-accumulate" them through the food chain. High concentrations of organochlorines, especially polychlorinated biphenyls (PCBs), have been associated with reproductive failure in marine mammals.
Partners in the study were the Marine Institute at the University of Aberdeen in Scotland, Dalhousie University in Canada and the British Antarctic Survey. Tissue samples from resident dolphins were obtained by using biopsy darts, which are fired into the dolphin from a crossbow.
These take a small sample of skin and blubber for analysis. It was the first time biopsy sampling of dolphins had been attempted in Ireland and was carried out under licence from Dúchas, the Heritage Service.
"If we want to understand what effects our activities are having on the environment, we should look at the marine environment and animals that live there," Dr Berrow says.
