Although there is a range of environmental conditions in which an animal can survive, there is an even smaller range of conditions in which it can thrive. New MEOPAR research examines the ability of marine fish and invertebrates off Eastern Canada, a globally important fishing region, to tolerate environmental change. The study, published in the journal PLOS ONE, finds that in the next fifty years, a number of regional species will experience conditions of low oxygen that may stress or kill them. The study also finds that species will likely face periods of stressful conditions over the next few decades due to variation in regional oxygen levels and temperature.
The Eastern Canadian fisheries of the Gulf of St. Lawrence and the Scotian Shelf are globally important fisheries. In 2014, commercial fishing on the east coast of Canada was valued at $2.4 billion (Fisheries and Oceans Canada). But the effects of climate change, such as increasing temperatures, increasing acidity, and lowered oxygen levels, are placing stress on marine fish and invertebrates, which could affect the fisheries’ viability in the future.
The study, which was led by former MEOPeer Catherine Brennan (pictured at right) during her time as a MEOPAR-funded postdoctoral fellow at Dalhousie University (Brennan is now employed at the Bedford Institute of Oceanography), saw Brennan and her colleagues use computers to model currents and physical characteristics, such as salinity and temperature, of the Gulf of St. Lawrence and Scotian Shelf. For this study, they set out to use the predictions of their model to understand how climate change will impact species in the region.
The research team identified 54 species of fish and invertebrates (such as clams and lobsters) that are important for the region's fisheries and/or ecosystem. The researchers reviewed current knowledge on species’ preferred and tolerated ranges of ocean acidity, depth, salinity, temperature and oxygen.
The study concludes that if the current trends of increasing temperature and decreasing oxygen continue, “many species will encounter unsuitable temperature or oxygen conditions within the next century,” and that some will do so in the next fifty years. In the case of ocean warming, Brennan explains, “Each species has a thermal limit, a maximum temperature above which they are not able to thrive. For example, Atlantic Cod, which inhabit the western Scotian Shelf, are at the upper boundary of their thermal limit, so any bit of warming that occurs in this region is going to be too warm for them.”
The study also considered that the region has the most variable sea surface temperature in the world: it’s here that warm Gulf Stream water mixes with Arctic currents. As a result of this variability, local species may feel the stress of climate change earlier than tthe modeled trends indicate. Brennan says, “The variability in the region is so large that it’s quite probable that species will be encountering unfavorable conditions in the near future.”
Brennan explains that some species’ habitats are moving, and some, due to interacting climate change impacts, are shrinking. “Demersal species, fish that are living closer to the bottom, species like the Atlantic Cod, they’re particularly threatened because their habitat is effectively being squeezed. The oxygen depletion near the bottom may be causing them to move upward, but the warming that could be closer to the surface, may be pushing them down,” said Brennan.
The researchers hope others will use and expand the open access dataset they compiled to better our understanding of the regional effects of climate change. “Our hope for the paper is that others will use the dataset and the references we’ve compiled in the paper to better explore species impacts.”
The study, Putting Temperature and Oxygen Thresholds of Marine Animals in Context of Environmental Change: A Regional Perspective for the Scotian Shelf and Gulf of St. Lawrence, was published in open access journal PLOS ONE, here. To access the dataset, go to the supporting information of the paper.
This work is part of MEOPAR’s Biogeochemical Projections under a Changing Climate project, led by Dr. Katja Fennel, Canada Research Chair II in Marine Prediction (Dalhousie University). Read more about the project here.