You will never guess, but salmon that survived the hot Holocene period, and the even hotter Eemian, will probably be OK in a slightly warmer world. Expert researchers found this surprising.
Given the broad spread of Salmon in the Northern Hemisphere, and their past survival through every single interglacial warm period of the Pleistocene, I would have thought that they could cope with quite a bit of climate change. As it turns out, they cope so well, that even salmon eggs that come from a 12C environment can be raised in an environment a whopping 8C warmer, and they were not noticeably any worse off.
Part of the concern with salmon was the spawning and eggs, and the problem with getting the salmon to shift their maternity wards and childcare arrangements (which they seem very attached too). But presumably those breeding grounds have varied before in temperature, and salmon didn’t die out, so — at least with this problem — nature has it figured out.
Map: Salmon and Climate Change, Fish in hot water, Red List.
Atlantic salmon also show capacity to adapt to warmer waters
Populations of Atlantic salmon have a surprisingly good capacity to adjust to warmer temperatures that are being seen with climate change, a group of scientists at the University of Oslo and University of British Columbia have discovered. The finding about Atlantic species adds to recent UBC-supported research on heat tolerance of Pacific salmon.
The new study, a collaboration between Norwegian and Canadian researchers, was recently published in Nature Communications. Funded by the Norwegian Research Council, it addressed questions around how climate change might affect salmon species distribution and abundance.
UBC authors of the study include Katja Anttila, a postdoctoral fellow who now works at the University of Turku in Finland, and Tony Farrell, Chair in Sustainable Aquaculture.
Scientists studied wild salmon from two European rivers. They compared a cold-water population from Norway’s northern Alta River, where water temperatures have not exceeded 18 C for 30 years, with warm-water populations from France’s Dordogne River, located 3,000 kilometres south, where annual water temperatures regularly exceed 20 C.
Eggs from both populations were hatched at the University of Oslo, where they were raised at 12 or 20 C. Despite substantially different natural environments, both populations had remarkably similar capabilities when warmed.
When reared at 12 C temperatures, salmon from both populations developed cardiac arrhythmias at 21 to 23 C, after a maximum heart rate of 150 beats per minute. But those raised at 20 C developed cardiac arrhythmias at a surprising 27.5 C, after the heart reached 200 beats per minute. Researchers found that increasing the fish’s acclimation temperature by 8 C raised temperature tolerance by 6 C.
“The results are surprising,” Farrell said. “A fish faced with uncomfortably warm temperatures might relocate or even die if it is too extreme. Here we have evidence for warm acclimation of a commercially and culturally important fish species.”
A 2010 study shows eggs of three salmon or trout species survive over an 8 – 16C range depending on the species. (see Table 1). The grown fish are happy over a 20 C range. Sea Surface temperatures have warmed by eight-tenths of a degree in the last 100 years.
That’s the thing about a scare over 0.8C of warming — the daily range, the seasonal spread, and the natural range of temperatures far exceeds the shift in long term trends (which have always changed themselves as well). Biology often copes.
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This study was done with climate change in mind. It’s the opening line….”Anthropogenic climate change is affecting species distributions and abundance…” . Commendably the researchers seem to have stuck with the observations and tossed out their hypothesis when it didn’t fit. Bravo.
DISCUSSION
Genetic differentiation between Norwegian populations was reported earlier and the Alta population aligns close to those populations. Current thinking is that the diversification among salmonid species and genetic isolation due to anadromy might be connected to climatic cooling during recent ice ages. Moreover, the prevalence of local adaptations increases with geographical distance, which led us to expect local adaption for the Alta population, where the river temperature has not increased above 18 C for at least the last 30 years, and the Dordogne population, which regularly encounter temperatures over 20 C in their natural habitat. In contrast to expectations, Alta and Dordogne populations differed very little in their acute cardiac response to temperature, but instead showed considerable cardiac plasticity in response to thermal acclimation that surprisingly was largely independent of the latitudinal and climatic origin of the populations. Therefore, for the most part we rejected thehypotheses of local thermal adaptation in these Atlantic salmon populations.
A little debate over evolutionary processes gets discussed too:
Therefore, the present results emphasize that acclimation remains a feasible possibility for survival in a warmer future, with physiological plasticity replacing the immediate need for local adaptation. If such plasticity enables Atlantic salmon to adequately respond to ongoing warming trends associated with climate change, the southern Dordogne salmon will be physiologically challenged by warming to a greater degree than the northern Alta salmon, because the capacity for cardiac acclimation to warm temperature still resides in the Alta population. The limited local thermal adaptation in Alta and Dordogne salmon populations contrasts with the apparently strong local adaptations revealed for Fraser River adult sockeye salmon (Oncorhynchus nerka) populations8. The most parsimonious explanation for such a species difference is the athletic requirement of the adult sockeye salmon for its once-in-a lifetime spawning migration, which has probably been a powerful selective force to optimize AS to local river migration conditions. Such selection may have been relaxed for Atlantic salmon.
The people of Norway and Finland appear to have paid for this research. Western wealth can support research that discusses and debates changes in the maximum heart rate (fHmax), aerobic capacity, and cardiac arrhythmias of different subtypes of a fish. I’m sure there are subtypes of people on Earth we don’t know as much about.
REFERENCE
Katja Anttila, Christine S. Couturier, Øyvind Øverli, Arild Johnsen, Gunnhild Marthinsen, Göran E. Nilsson, Anthony P. Farrell. Atlantic salmon show capability for cardiac acclimation to warm temperatures. Nature Communications, 2014; 5 DOI: 10.1038/ncomms5252
Elliot and Elliot (2010) Temperature requirements of Atlantic salmon Salmo salar, brown trout Salmo trutta and Arctic charr Salvelinus alpinus: predicting the effects of climate change, Journal of Fish Biology (2010) 77, 1793–1817, doi:10.1111/j.1095-8649.2010.02762.x (PDF)
Image: Salmon and Climate Change, Fish in hot water, Red List.