A research team led by University of Galway is investigating whether climate change is reducing the impact that some of the ocean’s smallest organisms have on carbon dioxide (CO2) levels in the atmosphere.
The researchers spent several weeks at sea on board the Marine Institute’s Celtic Explorer in the Labrador Sea between Canada and Greenland to record levels of phytoplankton.
Water samples and atmospheric measurements gathered by the researchers will help to assess how phytoplankton living on the sunlit ocean surface absorbs CO2 and nutrients, and in turn produces organic carbon.
The deployment of the UG instrument ASIP from the stern of the R/V Celtic Explorer. The ASIP is a cutting edge ocean robotic technology designed to study the surface ocean with unprecedented detail. Photo: Paul Stapleton
Some of this carbon which sinks into the deep ocean, locking in the greenhouse gas for centuries, and the unanswered question is how much carbon is exported – a process known as the biological carbon pump which plays a critical role in climate regulation.
This research is regarded as timely, given the growing interest in carbon dioxide removal (CDR) as a type of geoengineering.
One of the controversial methods proposed is to “fertilise” the ocean to stimulate phytoplankton with the aim of removing CO2 from the atmosphere. Several companies are already deploying methods to remove CO2 from the atmosphere.
The expedition is a follow-up to previous research in 2022. It was funded by the Marine Institute, and led by Prof Brian Ward, School of Natural Sciences, University of Galway.
It involved researchers from Dalhousie University, Nova Scotia, Canada and the Ocean Frontier Institute; Memorial University Newfoundland; and the Science Foundation Ireland research centre for applied geosciences -iCRAG.
The Labrador Sea in the North Atlantic is home to the largest sustained phytoplankton bloom annually, but it is believed that rapid changes are occurring in this region, and there are very few assessments of the biological carbon pump.
The micrometeorological mast attached to the bow of the R/V Celtic Explorer where direct measurements of the transfer of CO2 from the atmosphere to the ocean were carried out by the University of Galway team. Photo: Brian Ward
Current estimates suggest that the pump removes 5-12 gigatonnes of carbon from the atmosphere per year, roughly equal to anthropogenic CO2 emissions - the environmental change caused or influenced by people, either directly or indirectly.
The research project - Biological Carbon Export in the Labrador Sea (BELAS) – used a 10m mast on the bow of the Celtic Explorer to directly measure how much CO2 is being transferred from the atmosphere to the ocean.
Preliminary analysis indicates that an enormous flux of CO2 transfer occurred during the research expedition, driven by the abundance of phytoplankton photosynthesising in the surface waters.
The University of Galway team also measured the turbulence in the ocean down to 100m with their unique profiling instrument.
Turbulence is a critical process for controlling phytoplankton behaviour, which is just gaining recognition within the international community, they explain.
The Canadian scientists involved in the research project took water samples during the two week-long expedition, with the aim that their analysis will bridge the knowledge gap over the role of phytoplankton in the carbon cycle.
