Climate change will have vast—and in many cases unknown—consequences for ocean species and ecosystems as the chemistry of the water changes and it becomes warmer. Temperature change is occurring at a more rapid rate than ever anticipated. Smaller species respond to temperature change rapidly (in months) while large and cold-adapted species suffer. Warm water species have the ability to migrate north with the changing environment; for example, sardines have been noted to migrate north during warmer decades. Cold water species do not have this option.Ocean water is stratified. That means the density of the water is layered.
- Cool water results in weak stratification and high nutrients because the nutrients travel more easily. Result: a sub-arctic food chain with a lot of forage fish and few warm water predators.
- Warm water produces a more stratified ocean with fewer nutrients and lower productivity. Result: a subtropical food chain with a lack of forage fish and abundant predators.
- When cold water begins to warm, the distribution of nutrients changes and productivity is lower. Result: more predators and changes to the way the entire ecosystem interacts.
What can we expect?
SalmonThe salmon population around B.C. is more stable (in terms of climate change) than in some other areas because of distribution patterns. The acceptable geographical range of distribution is largely determined by temperature preference. Salmon do not like warmer temperatures because their metabolism speeds up and they grow at a slower rate. Near the edges of their distribution range there are ecologically significant thresholds where small changes will eliminate a stock. In the middle of the range (where B.C. is) there is more stability. B.C.'s and Alaska's glacier streams are cold and most productive for salmon stocks.
Climate variability has a powerful influence on salmon production; just a 1 to 2 degree swing in ocean temperatures can be associated with a doubling of salmon biomass between warm and cool eras. In B.C. and farther south, decreasing salmon populations have been observed during warm periods.
Data on steelhead catch rates show peaks at certain temperatures in the ocean (this is also true for sockeye, chum and pink). There are relatively narrow bands of temperature where they are found. Ocean surface warming will force sockeye and steelhead out of the Pacific and into cooler northern oceans.
Phytoplankton
Phytoplankton is at the base of the food web and anything that impacts this tiny species will have a trickle-down effect on the entire ecosystem. Phytoplankton feed on nutrients that move up from the depths of the ocean where they are abundant. If the ocean is too stratified because of warming water, nutrients cannot make it to the top, reducing the uptake of nutrients and productivity for phytoplankton.
Shells and corals
Shells and corals are at high risk from climate change through the acidification process. Calcifying organisms cannot form shells properly. With enough acidity the shells will dissolve faster than they can grow. Corals, both warm and cold water species, are unable to build their structures and grow.
Seabirds
Seabirds do well in the sub-arctic food web with prey and nutrients closer to the surface. Declines in seabird productivity can be expected in warm years. Some seabird species will migrate into northern climates with the warming temperatures.
Pacific sardines
Observations have shown that in warm years the spawning region of Pacific sardines expands greatly and shifts north. Interestingly, anchovies and sardines fluctuate in opposite directions with one taking over from the other; as one increases the other decreases along with temperature fluctuations.
Expected climate impacts on species can be complicated by changes in distribution, which has an impact on the interaction of species and ecosystems. In order to best manage the rapid changes it is important to observe and know as much as possible, and take into account what we do not know.
