• Plankton trawl reveals ten times the species

    Jan Piotrowski


Speed read

  • Researchers looked for plankton species at 334 sites around the globe

  • Plankton data will improve models of how oceans will respond to climate change

  • The need is urgent — studies are revealing plankton as a major factor in climate and fisheries

The number of known plankton species floating in our oceans has increased ten-fold thanks to an international study aiming to understand the impact of climate change.
Scientists from the Tara Oceans initiative say that this is a first step towards cataloguing the full diversity of marine life, which could in turn help to predict how stocks of fish and other marine resources will be affected in a warmer world.

“The survey has given us a beautiful first glimpse to the complexity of the system and shown us how much we still do not know.”

Mick Follows, Massachusetts Institute of Technology

Plankton is crucial to climate modelling, because phytoplankton, tiny plant organisms, produce more than half of the planet's oxygen. Phytoplankton and their animal cousins zooplankton also sequester large amounts of carbon from the atmosphere when they die and sink to the ocean floor.
Despite this, existing climate models represent the impact of plankton in only the most rudimentary sense, says Eric Karsenti, the research director of Tara Oceans, a France-based expedition funded by the UN and others.
Karsenti says that Tara’s work will improve models by making their representations of how plankton interacts with its marine home more realistic.
In a paper published in Science last week (22 May) by the Tara Oceans initiative, researchers describe how they used genetic analysis to identify the number of different plankton species found at 334 separate sites across the globe.
They found 110,000 unique species, but the data suggest the real figure could actually be closer to 150,000. Just 11,000 species had been described previously, so these findings greatly improve humanity’s understanding of the marine ecosystem, the paper states.
The findings are also expected to improve plankton monitoring in the future. Scientists can already predict the make-up of plankton communities based on the temperature of the water.
But Karsenti says that teams from Tara Oceans are working on tools to measure other environmental factors that affect plankton, such as pollution levels and ocean acidification. Adding these extra levels of complexity will further enhance modelling accuracy, he says.
The urgency to understand plankton for climate prediction is underlined by a recent study which found that these microscopic plants could cause up to 20 per cent more ice melt in the Arctic than existing models predict. Similar effects are seen on land where microorganisms cover glaciers and ice packs. Having more information about microorganism ecology could also be useful beyond climate modelling, says Mick Follows, a professor of oceanography from the Massachusetts Institute of Technology. 
He says that plankton communities may change in a warmer world, with creatures becoming smaller for instance, which would have a knock-on effect on commercial fish species. Understanding this process will be particularity relevant to developing countries with large coastal communities, where seafood accounts for up to half of the animal protein in people's diets.
But there is still a long way to go before these kinds of questions can be answered reliably, says Follows. "The survey has given us a beautiful first glimpse to the complexity of the system and shown us how much we still do not know."