المواد الكيميائية السامة تهدد الحيتان القاتلة
September 27, 2018 - Marine pollution is pushing the world’s killer whale population ever closer to extinction, with chronic exposure to PCBs (polychlorinated biphenyls) threatening the reproductive and immune systems of the largest member of the dolphin family.
Due to their voracious appetites and their place at the apex of the ocean food chain, killer whales (Orcinus orca) are considered as an “indicator species” regarding the health of marine ecosystems worldwide.
A study of PCB concentrations in the blubber of 351 orcas around the world concludes that the chemical is easily transferred to offspring and endangers the long-term viability of more than 50% of the world’s killer whale population.
Researchers led by Pierre Desforges at Aarhus University in Denmark developed a risk assessment model capable of forecasting the effects of PCB exposure on these creatures in the world’s oceans, and over the next 100 years.
The results of the researchers’ model simulations show that concentrations in orcas are closely tied to proximity to PCB production and use and that high levels of the chemical have a significant impact on both population size and sustainability.
While the production of PCBs was banned in the United States in 1978, their widespread industrial use led to ubiquitous global distribution.
According to the model, orca populations in the Arctic and Antarctic, where PCB concentrations are low, will continue to grow, or only be modestly reduced.
According to Desforges and colleagues, in regions where concentrations are highest -- Japan, Brazil, the northeast Pacific, the Strait of Gibraltar and the UK -- orca populations could be headed for a complete collapse within the next century.
The study is published in the September 5 issue of the journal Science.