Ecosystems

Looking out to the ocean from a rocky beach with a large rock in the foreground. The sky is a grey, twilight colour with an orange setting sun on the horizon and there are tall evergreens in the distance to the right.
Clouds | Photo by Barb Dinning

Climate change will affect ecosystems throughout the region. The vulnerability of marine species to the cumulative effects of climate change depends on intrinsic adaptive capacities and sensitivities (based on biological or ecological traits), and extrinsic threats (impacts), such as increasing sea surface temperature or ocean acidification [86]. The cumulative effects of climate change on the food webs of the northeast Pacific may lead to a 30% reduction in total ecosystem biomass [17].

Air Temperature and Precipitation

Air temperatures are projected to increase at 0.3⁰C per decade in BC [72], still less than is expected across the country as a whole [43]. Melting glaciers will result in higher spring time water discharge into streams and rivers in the short term, while over time glacial retreat will likely lead to reduced water levels in glacier-fed streams, particularly during summer [10].

Due to the reduction in snowpack associated with decreased winter precipitation and warmer air temperatures, the spring runoff (freshet) will likely occur earlier in the spring in many rivers. This will have downstream effects on freshwater habitats, and linked marine systems [10,21], which will already be warmer and less oxygenated. These changes are likely to negatively impact the reproductive capacity and survival of fish and other aquatic species [6,87]. The sheer increase in freshwater volume entering coastal marine waters will also affect salinity and stratification of ocean surface waters.

Increased precipitation may lead to more runoff of contaminants and terrestrially derived nutrients – which, when combined with higher water temperatures, could increase the likelihood of toxic algae blooms in freshwater and marine ecosystems [29]. The increase in freshwater volume entering coastal marine waters may also decrease sea surface salinity and of ocean surface stratification. These stressors are likely to affect marine fishes and mammals that depend on nearshore habitats and are adapted to current oceanographic conditions [29].

Sea Level Rise

Sea level rise may affect coastal ecosystems through changes to habitat, especially for nearshore areas if important intertidal habitat becomes permanently sub-tidal, affecting nearshore plants, algae, and shellfish. Sea level rise is likely to cause an increase in the inland penetration of salt water in tidal systems. The abundance and species composition of coastal plants and algae, along with associated invertebrate habitats, could be altered if important intertidal habitat becomes permanently sub-tidal as sea levels rise [29].

Generally, coastal sensitivity to sea level rise depends on the physical geology of the coastline, and as such low-lying sandy regions will be most impacted. Most of the shoreline of BC has low sensitivity to sea level rise due to the rocky, fjordal coastline, but some areas (near Prince Rupert, Bella Bella, and most of Vancouver Island) are moderately sensitive (based on a recent provincial shoreline sensitivity analysis; [23]). Highly sensitive areas within the MaPP region include the northeast corner of Haida Gwaii [9,44]. For both the MaPP region and sub-regions, some moderate and high sensitive areas correspond with culturally important (First Nations) archaeological sites (see Map Section: Archaeological Sites Sensitive to Sea Level Rise Map, MaPP Region).

Sea Surface Temperature

Increasing sea surface temperatures are likely to affect zooplankton biomass, contributing to overall biomass declines of lower trophic level species [29]. Increasing ocean temperature and the northerly shift in the California Current may lead to higher abundance of low nutrient zooplankton, which would in turn affect juvenile fish species such as herring and salmonids [60,88]. Phytoplankton species composition is also likely to change, which could also affect higher trophic levels who depend on high quality zooplankton [17,58,60,89]. Kelps (giant kelp and bull kelp) and eelgrass (Zostera marina) are also likely to be negatively affected by warming sea surface temperatures; the cumulative impact of temperature along with decreasing salinity and increasing sedimentation from runoff will influence the productivity and distribution of these important habitat forming species [6].

Ocean Acidification

Ocean acidification will certainly continue to affect coastal BC [52], although there are significant knowledge gaps in terms of the effects of ocean acidification on marine organisms (Appendix 2 Table 2). Where data exist, it is more reliable for commercially viable shellfish species (e.g. oysters and other shellfish) and issues that may affect human health (e.g. harmful algae blooms) [52]. Already, the ocean below 300m depth is corrosive to aragonite shells, and it is likely that the saturation depth will continue to decrease, threatening shelled organisms and the fishes that feed on them, including Pacific salmon [4,52]. There is a strong likelihood that the negative impacts associated with ocean acidification could increase rapidly, and that the effects on marine species could potentially cause large shifts in species distribution and community assemblages across both latitude and depth [54].

Ocean acidification may affect habitat availability and the abundance of those species dependent upon calcifying organisms for structural habitats, and those whose larval stage is affected by a decrease in pH. For example, by 2100, cold water corals are projected to degrade due to ocean acidification, which will affect habitat availability for fish populations, therefore affecting fisheries productivity [54]. The effects of ocean acidification on trophic dynamics (food web interactions) and the synergistic effects of ocean acidification with other climate change projections, such as increasing ocean temperature and declining oxygen levels, are uncertain and requires further research [52,63].

Ocean deoxygenation

Ocean acidification will certainly continue to affect coastal BC [52], although there are significant knowledge gaps in terms of the effects of ocean acidification on marine organisms (Appendix 2 Table 2). Where data exist, it is more reliable for commercially viable shellfish species (e.g. oysters and other shellfish) and issues that may affect human health (e.g. harmful algae blooms) [52]. Already, the ocean below 300m depth is corrosive to aragonite shells, and it is likely that the saturation depth will continue to decrease, threatening shelled organisms and the fishes that feed on them, including Pacific salmon [4,52]. There is a strong likelihood that the negative impacts associated with ocean acidification could increase rapidly, and that the effects on marine species could potentially cause large shifts in species distribution and community assemblages across both latitude and depth [54].

Ocean acidification may affect habitat availability and the abundance of those species dependent upon calcifying organisms for structural habitats, and those whose larval stage is affected by a decrease in pH. For example, by 2100, cold water corals are projected to degrade due to ocean acidification, which will affect habitat availability for fish populations, therefore affecting fisheries productivity [54]. The effects of ocean acidification on trophic dynamics (food web interactions) and the synergistic effects of ocean acidification with other climate change projections, such as increasing ocean temperature and declining oxygen levels, are uncertain and requires further research [52,63].

Sea surface salinity

Changes in salinity can affect both sexual reproduction and vegetative propagation of seagrasses [29,90]. Declining salinity levels may affect the habitat, survival, and growth of marine fish and shellfish; in the Arctic, declining salinity has been shown to reduce phytoplankton size, which in turn affects productivity of higher trophic levels [54].

Other impacts

Changes in the timing of spring currents is also likely to affect biological interactions such as plankton availability, in turn affecting larval fish and invertebrates [29]. These changes could negatively affect marine fish and invertebrate recruitment, but the specifics of this impact are currently unknown [29].

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