Climate change will hit plankton severely damaging fisheries and marine food chain
The impacts of climate change can even extend to plankton - marine organisms invisible to the human naked eye - which produce half of the oxygen available in the atmosphere and form the basis of the food chain in oceans. This may, in turn, have a ripple effect on other fish and whales that feed on them, say scientists.
But plankton decline will most likely happen in the polar regions, which are vulnerable to the warming ocean temperature, according to two studies published in Cell.
Plankton - plants and animals that float along at the mercy of the sea's tides and currents - plays an important role in the ocean ecosystem. Besides being the food source for larger organisms such as fish and whales, they generate oxygen and capture carbon from the atmosphere and transfer it to the deep ocean. "They are also sensitive to climate change so we could consider them as canaries in the coal mine to signal changes in the ocean", Chris Bowler, a CNRS research director in Paris and one of the authors of the study, told MEA WorldWide (MEAWW).
The authors claim that their studies provide a peek into the future health of the ocean and the planet. The change in plankton distribution may alter the variety of food on offer for the larger organisms, or it could change how the ocean stores carbon. "And if Arctic plankton is replaced by other plankton, for example, from the Atlantic, then it may affect the functioning of the entire Arctic ecosystem," Bowler told MEAWW.
In an effort to reverse the decline in the health of the world's oceans, the United Nations (UN) has declared 2021 to 2030 to be the Decade of Ocean Science for Sustainable Development.
The two studies set out to provide additional insights into the potential impacts of climate change on marine biodiversity. They analyzed results gathered from the 2009-2013 Tara Oceans expedition, which investigated planktonic and coral ecosystems in the face of the changing climate.
The objective behind the first study was to map these organisms on a global scale and understand how they could respond to climate change.
Building on the distribution of the current population of plankton across the globe, the team predicts that an increase in ocean temperature will boost the population near the equator, leaving the ones dwelling near the poles and the temperate zones - the region between the poles and the equator - at risk. "Our results clearly show that the planktonic diversity is more important around the equator, and decreases towards the poles”, explains Lucie Zinger, an ENS - PSL assistant professor and author of the first study.
The second study dug a little deeper. To understand the capacity of microbes in adapting to changing environmental conditions, they read the genes of these organisms. "This analysis allowed us to study not only what ocean microbes are capable of doing, but also what they actually do at a global scale", says Shinichi Sunagawa, from the Institute of Microbiology and Swiss Institute of Bioinformatics at ETH Zurich and senior author of the second study.
Sunagawa adds that the plankton population in the equators - warmer waters - are more adapted to the changing environmental conditions than the ones at the poles. Those residing near the equator will continue to thrive, thanks to a pool of genes that help them adapt to the warmer conditions. On the other hand, plankton in polar waters may not fare well because they lack these adaptive genes, the study says. As a result, the study predicts, that plankton in polar water could disappear and be replaced with new species from warmer waters.
Plankton distribution impact
The change in plankton distribution may change the variety of food on offer for the larger organisms, or it could change how the ocean stores carbon. "And if Arctic plankton is replaced by other plankton, for instance, from the Atlantic, then it may affect the functioning of the entire Arctic ecosystem", Bowler told MEAWW.
"Consequences of this are still unclear, so we consider our study to be the first glimpse at climate change impacts on these complex communities and where they will be the most important", Zinger told MEAWW. But temperate regions that exist between the equator and poles are currently very important for fisheries and carbon capture. Our predictions show that these areas should experience the strongest changes in distribution, and we believe that our results will prioritize and stimulate further studies aiming at understanding more precisely how these changes will impact fisheries stocks, Carbon capture and the like, he explains.
Further studies need to continue to observe the oceans so we can follow the changes as they occur and use it to improve our understanding about how ocean life adapts to environmental change, says Bowler.