The stern of the RV Celtic Explorer, deploying a measurement instrument. Image: Paul Stapleton
By learning more about phytoplankton’s role in reducing CO2, some believe the process could be scaled up to further reduce global emissions.
A group of Irish researchers took to the Arctic waters to examine the role tiny organisms in the ocean play in reducing global carbon emissions.
A team from the University of Galway spent several weeks at sea on board the Marine Institute’s Celtic Explorer to record the levels of phytoplankton – microscopic plant-like organisms in the ocean. Phytoplankton that live on the ocean surface absorb CO2 and nutrients, which turn into organic carbon.
Some of this carbon sinks into the deep into the ocean, which can lock the greenhouse gas away for centuries. This process is known as the biological carbon pump and plays an important role in climate regulation. But the Irish researchers say there is more to learn about how important phytoplankton are to this process and if the climate crisis is causing an impact.
“The interplay between the physics and biology of phytoplankton and their role in the carbon cycle, and how climate change is affecting this, is not well understood,” said Prof Brian Ward, who led the expedition. “Our current ability to predict changes in the biological carbon pump in the face of ongoing and future climate change is weak at best.”
The Celtic Explorer went to the Labrador Sea between Canada and Greenland, which is home to a large phytoplankton bloom every year. The team used a 10-metre mast on the bow of the research vessel to measure how much CO2 is being transferred from the atmosphere to the ocean. The preliminary analysis indicated that an enormous flux of CO2 transfer occurred during the research expedition, due to the massive amount of phytoplankton on the water.
The researchers estimate that the biological carbon pump removes between five and 12 gigatonnes of carbon from the atmosphere per year. But Ward says there is “mounting evidence” that the climate crisis is impacting this process.
Canadian scientists involved in the research project took water samples during the two-week expedition, which will be analysed to learn more about how phytoplankton contribute to the carbon cycle.
The research comes amid a growing interest in carbon dioxide removal (CDR), where one of the controversial methods proposed is to ‘fertilise’ the ocean surface with artificial iron to stimulate phytoplankton growth with the aim of removing CO2 from the atmosphere.
“There remains fundamental research to be carried out before we can scale up the removal of CO2 using the proposed fertilisation methods,” Ward said. “There is no doubt the concentration of CO2 in the atmosphere needs to be reduced by the end of this century, but CDR methods are unlikely to offset anthropogenic [human] CO2 emissions, which is where the main focus needs to be.”
The research included support from Canada’s Dalhousie University, the Ocean Frontier Institute and iCRAG, the Science Foundation Ireland Research Centre for Applied Geosciences.
Not all phytoplankton is beneficial however. Karenia is a particularly harmful phytoplankton, which can cause red hues in the water and considerable ecological damage from its toxic blooms.
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