Killer whales are an iconic species in the world’s oceans. They are also at the top of the food chain and able to concentrate persistent pollutants to very high levels, a new study carried out by GMIT and the Marine Institute shows.
The study, published in the Marine Pollution Bulletin, has shown levels of persistent pollutants in four stranded killer whales are very high and may exceed the toxicity threshold which can lead to significant health effects. The role that high concentrations of persistent pollutants may have played in their possible cause of death is not known.
The GMIT and Marine Institute teams analysed blubber samples from three killer whales stranded in Galway, Mayo and Waterford between 2010 and 2017, one of which was pregnant with a near term foetus, which was also sampled.
Killer whales though frequently sighted in Irish waters rarely strand and these samples provide a great opportunity to screen these top predators for a range of pollutants. The study showed bio-accumulation of 16 polychlorinated biphenyls (PCBs ), seven brominated flame retardants and 19 organochlorine pesticides. Concentrations of PCBs in one killer whale, stranded at Doohoma, Co Mayo, exceeded the suggested toxicity threshold of 17mg/kg.
Senior author Moira Schlingermann, a PhD student at GMIT, said that “although these concentrations are high, these results are relatively low from a global perspective, particularly in comparison to the highly contaminated transient killer whales from coasts along the north-east Pacific Ocean”.
“These contaminants are known as legacy pollutants as they were produced decades ago but still persist in our marine waters. We are also interested in “emerging” pollutants, new chemicals that have only recently been designed and released into our environment and for which we do not know their effects,” said Ms Schlingermann who will be exploring concentrations of these emergent pollutants in a range of whale and dolphin species as part of her PhD.
The cocktail of legacy and emerging pollutants, together with other pressures these marine mammals face from noise pollution to the availability of prey, can provide multiple stressors on these top predators.
“Persistent pollutants continue to be of major concern for marine apex predators such as killer whales and it is vital that they are continually monitored and reported in order to add to the knowledge of pollutants across the entire range of this species,” said Ms Schlingermann.
Dr Philip White of GMIT, who in conjunction with Dr Brendan McHugh from the Marine Institute supervised much of this work which was carried out in the Marine Institute laboratories in Oranmore, Co Galway said that while the levels of persistent organic pollutants in these samples are high, it must be noted that whatever toll it takes on the animal’s health must be further studied in order to properly quantify the effect on reproduction, immunosuppression and the overall health of the animals.
“To this end, GMIT will continue to provide analytical support to the project in the hopes of gaining a greater knowledge of the effects of persistent, as well as new and emerging compounds of concern, on this renowned and much-loved whale species,” he said.
Dr Simon Berrow, co-supervisor at GMIT and CEO of the Irish Whale and Dolphin Group (IWDG ), which is part-funding this PhD suggested the build-up of persistent pollutants and their effects on these animals’ reproduction are undoubtedly the biggest long term threat they and species of dolphin and porpoise face in our oceans.
“We have to do everything we can to prevent these substances entering the marine environment and the food chain, because once in it, they will be almost impossible to remove,” he said.
Dr Ian O’Connor of the Marine and Freshwater Research Centre at GMIT said this work represents a continuation of their long running research collaboration with the Marine Institute and the IWDG focused on conserving marine biodiversity by assessing the response of aquatic species to human impacts and environmental stressors.”
