climate change puts plankton in motion

The climatic changes that have warmed the world's oceans have caused a "disturbing" migration north of some communities of the smallest marine organisms: plankton.

This is the conclusion of a new research published Thursday in the journal Nature examine the composition of plankton communities in the northern hemisphere.

Unpretentious creatures are sometimes referred to as "building blocks" of the ocean because of their importance in the food chain, and their apparent migration is another indicator of the profound effect of climate change on the planet.

"This is not good news for marine ecosystems," said Lukas Jonkers, lead author of the study and postdoctoral researcher at the Center for Marine Environmental Sciences of the United States. University of Bremen.

"We find that we have pushed back the marine ecosystems, or at least this zooplankton group, from their natural state, which I think is very disturbing," he told AFP.

"This means that even if we manage to keep the rise in global temperature below 1.5 degrees, which is doubtful, ecosystems around the world will probably be deeply affected."

The object of research is the organism known as the planktonic foraminifer, a kind of plankton with a hard shell.

When these ubiquitous creatures die, they fall to the bottom of the ocean like snow and their sturdy shells are able to withstand the ravages of time.

This means that they create an indispensable and unprecedented record of what plankton communities in different parts of the world have looked like for centuries.

And this recording solves a long-standing problem for researchers trying to examine how marine life has been affected by climate change – a clear baseline.

Jonkers decided to exploit the record and compare the samples collected in the modern era, between 1978 and 2013, with ocean floor sediments dating back several centuries.

What he discovered was that modern plankton communities often do not look much like the sediment communities listed below.

Instead, modern communities resembled recording sediments in more southerly waters, suggesting that plankton species migrated north, with water temperatures becoming more similar to initial habitat.

Clear change model

"It's all headed north," Jonkers said.

"On one site you will always find many different species, but we now see that this species community is made up of different species that prefer warmer water."

For example, the modern species observed near Greenland are the same as the preindustrial sediments found further south.

The study examined nearly 4,000 samples from various areas of the northern hemisphere. It is therefore difficult to know how modern plankton communities in southern waters compare to their predecessors in these tropical regions.

But Jonkers said the pattern of change in the places studied was clear.

"Where the temperature has changed more, the species has changed more."

It was not possible to set a specific timeframe for the change, but Jonkers said it seemed to be incremental.

And until now, he said, there was no evidence of extinction of species, but simply of moving communities from one place to another.

But migration could be a problem for plankton and the animals that depend on it for food if newcomers do not adapt quickly enough to survive among other people in their warmer environments.

The research joins a growing body of evidence on how climate change is affecting oceans.

In March, a study team on seals and whales in the Arctic discovered that animals were forced to change their eating habits while the ocean was warming up, melting the ice and prompting fish stocks to move.

© 2019 AFP