University of British Columbia researchers
studying the marine food web of the Northeast Pacific Ocean have found that the
exposure and accumulation of chemical pollutants, such as polychlorinated
biphenyls (PCBs) and organic mercury, will be exacerbated under climate change.
The study, published recently in Scientific
also found that this would increase the accumulation and risk of exposure to
these pollutants and their toxic health effects, on both mid-level predators
like chinook salmon as well as top predators like resident killer whales.
“This has serious implications,” said lead
author Juan José Alava, a researcher at the UBC Institute for the Oceans and
Fisheries’ OceanCanada Partnership and Nippon Foundation-UBC Nereus Program.
“All of the southern resident killer whales that exist along the Pacific
Northeast Coast eat chinook salmon, which is their primary diet. These iconic
whales are already facing many anthropogenic impacts—ship traffic, underwater
noise, marine pollution—and they will be further impacted by increased
pollutant bioaccumulation driven by climate change.”
Researchers focused the study on the Northeast
Pacific marine ecosystems such as the Strait of Georgia, offshore waters of
Haida Gwaii, the west coast of Vancouver Island and Puget Sound. They found
that, for killer whales, concentrations of organic mercury are projected to
increase by eight per cent and PCBs by three per cent in a “business as usual”
or high CO2 emission scenario. However, in a low emission scenario where CO2
levels are strongly reduced, concentrations of organic mercury are projected to
increase by one per cent and PCBs by less than one per cent.
Worse, for chinook salmon, the levels of
pollutants are projected to be almost 10 percent higher for both organic
mercury and PCBs than levels for killer whales.
Alava noted that in recent years the Pacific
Coast has seen a decline in the chinook salmon population, likely due to the
impact of ocean warming. Now this species of salmon will also likely be
impacted by increased pollutants in their food web, magnified under climate
change, the study has found.
“Our marine ecosystems are threatened by
multiple global and local stressors, including climate change and pollution,
from human activities acting simultaneously and interactively,” said co-author
William Cheung, associate professor in the Institute for the Oceans and
Fisheries, director of science at the Nippon Foundation-UBC Nereus Program, and
a principal investigator of the OceanCanada Partnership at UBC. “Our study
suggests that reducing pollution have the co-benefits of lowering the threats
of climate change to vulnerable animals such as salmon and killer whales.”
“This study underscores the urgent need for
contaminant management and control and potential pollution mitigation policies
including, limiting and preventing mercury and greenhouse gas emissions from
human activities and fossil fuel and coal burning. This is of paramount
importance as Canada has yet to accomplish the mitigation and reduction of CO2
levels committed at the Paris Agreement,” said Alava.