Marine species in ambient low‐oxygen regions subject to double jeopardy impacts of climate change

Abstract

We have learned much about the impacts of warming on the productivity and distribution of marine organisms, but less about the impact of warming combined with other environmental stressors, including oxygen depletion. Also, the combined impact of multiple environmental stressors requires evaluation at the scales most relevant to resource managers. We use the Gulf of St. Lawrence, Canada, characterized by a large permanently hypoxic zone, as a case study. Species distribution models were used to predict the impact of multiple scenarios of warming and oxygen depletion on the local density of three commercially and ecologically important species. Substantial changes are projected within 20-40 years. A eurythermal depleted species already limited to shallow, oxygen-rich refuge habitat (Atlantic cod) may be relatively uninfluenced by oxygen depletion but increase in density within refuge areas with warming. A more stenothermal, deep-dwelling species (Greenland halibut) is projected to lose ~55% of its high-density areas under the combined impacts of warming and oxygen depletion. Another deep-dwelling, more eurythermal species (Northern shrimp) would lose ~4% of its high-density areas due to oxygen depletion alone, but these impacts may be buffered by warming, which may increase density by 8% in less hypoxic areas, but decrease density by ~20% in the warmest parts of the region. Due to local climate variability and extreme events, and that our models cannot project changes in species sensitivity to hypoxia with warming, our results should be considered conservative. We present an approach to effectively evaluate the individual and cumulative impacts of multiple environmental stressors on a species-by-species basis at the scales most relevant to managers. Our study may provide a basis for work in other low-oxygen regions and should contribute to a growing literature base in climate science, which will continue to be of support for resource managers as climate change accelerates.

Climate Change Vulnerability of American Lobster Fishing Communities in Atlantic Canada

“…Ocean temperatures on the continental shelves off the Northeast USA and southern Atlantic Canada have increased over the past half century (Jewett and Romanou, 2017;Greenan et al, 2018b), consistent with the global trend of increasing ocean heat content resulting from climate change (Cheng et al, 2017). The resulting biological impacts vary both regionally and by species (Fogarty et al, 2007;Wernberg et al, 2011;Pinsky and Fogarty, 2012;Shackell et al, 2014;Stortini et al, 2015Stortini et al, , 2017Kleisner et al, 2016Kleisner et al, , 2017. As warming continues, conditions may become uninhabitable for some species while others may flourish (Sorte et al, 2010).…”

“…While CIVI is comprised of exposure (natural forces), infrastructure, and socio-economic indicators, it does not incorporate biological impacts of climate change. In the second part of the analysis, a species vulnerability index will be calculated as a function of exposure (gain/loss in suitable habitat) and sensitivity (measures of abundance, potential, and food availability) (Stortini et al, 2015(Stortini et al, , 2017, based on projections of change in suitable habitat (Shackell et al, 2014). The objective of this paper is to integrate relevant information at the spatial scale of a stock.…”

Projections of Future Trends in Biogeochemical Conditions in the Northwest Atlantic Using CMIP5 Earth System Models

“…However, they do not adequately represent all the biogeochemical conditions in the ocean, particularly in shelf areas, and they have difficulty representing the complex dynamics of the northwest Atlantic where our regions of interest, the GSL and the Scotian Shelf, are located. Better projections of future biogeochemical conditions in the GSL and on the Scotian Shelf are needed in order to assess the impact of climate change on different marine species (Bianucci, Fennel, Chabot, Shackell, & Lavoie, 2016;Stortini, Chabot, & Shackell, 2017). To obtain better projections for these regions, we are developing a coupled regional climate model that uses future trends from the ESMs at its open boundaries.…”

Declining oxygen in the global ocean and coastal waters

“…Through this mechanism, ocean warming is predicted to result in shifts in the distribution of fishes and invertebrates poleward by tens to hundreds of kilometers per decade, shifts into deeper waters, and local extinctions (63,86). Models project that warming combined with even modest O 2 declines (<10 mmol kg −1 ) can cause declines in important fishery species that are sensitive to low oxygen levels (87). Physiological oxygen limitation in warming waters is also predicted to reduce maximum sizes of many fish species, including some that support important fisheries (88).…”