marine organisms (algae, corals, plants, fish…) can escape from the increase of temperature that are experiencing seas and oceans by climate change by moving to other places (towards the poles), or they may undertake a migration that will take them to greater depths (vertical). A team of researchers from the Spanish Institute of Oceanography (IEO), the Consejo Superior de Investigaciones Científicas (CSIC) and the University Kaust has been calculated that, on average, species should migrate to the seabed by decade by 18.7 meters on an emissions scenario of moderate greenhouse gas emissions —guilty of global warming— and 32,3 meters with high emissions to keep a temperature constant until 2100. To be an average, there are considerable variations throughout the planet, they say. The research has taken as reference the scenarios developed by the IPCC (a panel of UN experts who study climate change).
“With this study we have shown that the strategy of vertical migration is viable, but it is limited,” says the scientist, Gabriel Jorda, first author of the study published today in Nature Ecology & Evolution. “It is similar to what happens on earth, where the species go up in height to find the temperatures to which they are accustomed,” he adds. What is likely is that the different species “may opt for a combined solution between adaptation thermal, migration, horizontal and vertical,” he says.
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But even though manage to find the right environment, these organisms will encounter some problems, because the temperature is not the only factor limiting their survival. The time will come when they will have fallen to deep waters where there is sufficient light for the plants, algae, and microalgae such as phytoplankton or corals to perform photosynthesis. “This in turn involves that herbivorous fishes that have also moved not to find food,” says the researcher. In addition, there are insurmountable physical boundaries: when touch the background will no longer be able to go beyond. Some circumstances that already meet the species that live in shallow waters such as coral, kelps (large seaweeds) and seagrasses. “These species will experience a vertical compression of their habitat as temperatures rise,” explains Jorda.
The organisms that they are most likely to suffer at the global level are the corals. Can’t go down much more and in horizontal displacement is also limited by the thermal conditions of tropical zone with minimum temperatures warm. “At the end of this century, its habitat could be reduced by 75% and by migration towards the poles the species would earn a 7% of space, but clearly does not compensate the losses”, warns the researcher Núria Marbà. In areas like the coral Triangle —an area of the Pacific is considered the greatest biodiversity in the world with 76% of coral species known— the projections of the study indicate a reduction of 50% of the corals already, “between next year and 2025 under the worst emissions scenario”.
For the large algae known as kelps, the researchers have calculated that they will experience a decline until the end of the century of 25%. But they have an advantage, because they can expand into areas more polar, as the meadows. “Neither will compensate for the habitat that will be lost, but have more travel than the corals,” he adds Marbà.
In the Mediterranean, the meadows of posidonia are going to suffer significant losses during the second half of this century. “They are very sensitive to heating, when it reaches 28 degrees already visible mortality”, explains the scientist. But there are other angiosperms (cymodocea nodosa), in the present, less abundant than posidonia, which tolerate more than 30 degrees of temperature, so “the warming will stimulate its growth.” “A will decrease but the other will expand”, the specific expert. Other angiosperm that entered the Mediterranean through the Suez canal, which has already reached Sicily and Naples, is also knocking on the door and “can continue to move forward”.
