Global warming is already radically changing many marine ecosystems. Killing corals. Pushing tropical species such as scorpion fish or puffer fish into our woes. Causing huge and frequent jellyfish blooms, which fill the Mediterranean with these annoying marine animals. Already today there are too many examples to cite exhaustively. But it could be even worse in the future: according to a study just published in Nature, the increase in temperatures expected in the coming decades could make large areas of the Earth’s oceans uninhabitable for many species of plankton, with potentially disastrous consequences for the entire food chain that is based on these microscopic marine microorganisms.
The study
“Plankton is the lifeblood of the oceans, fundamental both for the food chain and for fixing carbon in the water,” explains Rui Ying, researcher at the University of Bristol and co-author of the study. “If its existence were endangered, it would be an unprecedented threat, which could destroy entire marine ecosystems with devastating and far-reaching consequences for ocean life and human food security.”
For this reason, the authors of the research decided to investigate how one of the most widespread classes of microorganisms that make up zooplankton, the foraminifera, could adapt to the rapid increase in temperatures predicted by climate models in the coming decades. And to do so, they decided to look to the past: about 21 thousand years ago, when the end of the last ice age produced climate changes similar to those we are observing in recent years.
Risk of extinction
Using the available fossil evidence, and a model that allows us to study the spread of plankton in the oceans in relation to changes in climatic conditions, the authors of the study obtained an estimate of the effects of the warming of the waters that occurred at the end of the ice age, and of those that would have a similar increase in temperatures over the current century.
According to their findings, 21,000 years ago foraminifera were unable to keep up with the sudden increase in temperatures, and moved north towards the cool waters near the poles, drastically reducing their presence in lower latitudes. On that occasion, the changes were gradual enough to allow the survival of these animals, and their subsequent return to more southern waters. But the same is unlikely to happen again if temperature increases are as drastic as expected.
“The fossil record shows that plankton moved from warmer oceans in the past to survive,” Yiung clarifies. “But using the same ecological and climate model, projections show that current and future rates of warming are too high for this to happen again. It is possible that these precious organisms will be swept away from our oceans.”