Ecimat’s mesocosm facility hosted an international experiment involving researchers from Greece, Italy, France, Finland and the United States
Over the past few weeks, the mesocosm facility at the Marine Research Centre (CIM) of the University of Vigo hosted an international research team carrying out an experiment to investigate how marine plankton communities respond to ocean alkalinity enhancement under future ocean warming scenarios.
The study, conducted at Ecimat, brought together researchers from Greece, Italy, France, Finland and the United States through the transnational access programmes of the Iriscc and Aquaserv projects. The research focused on ocean alkalinity enhancement, a process that increases the alkalinity of seawater to promote the uptake and long-term storage of CO₂ while maintaining stable ocean pH. It is one of the climate mitigation approaches currently under evaluation because, in addition to removing atmospheric CO₂, it may also help reduce ocean acidification caused by carbon dioxide emissions.
The aim of this international experiment was to assess the effects of ocean alkalinity enhancement on the organisms that form the base of the marine food web when applied under the climate conditions expected in the coming decades.
Assessing the response of the entire plankton community
The study was carried out during the second half of June and was coordinated by CIM researcher Pablo Serret. Twelve researchers from Spain, Greece, Italy, France, Finland and the United States took part in the experiment.
Twelve mesocosms were used and divided into four experimental treatments: three control units, three with increased alkalinity, three with seawater temperatures raised by three degrees Celsius, and three combining both increased alkalinity and warming.
“This experimental design will allow us to distinguish the effects of alkalinity enhancement from those of warming and, above all, to understand how both factors interact,” explains José González, head of Ecimat’s Oceanography Unit.
Throughout the experiment, researchers analysed the response of the entire plankton community—from viruses and bacteria to phytoplankton and zooplankton—to determine whether ocean alkalinity enhancement could alter the functioning of marine food webs in a warmer ocean.
A promising climate mitigation strategy
According to researcher Pablo Serret, “the difficulty of reducing global greenhouse gas emissions at the pace required is making atmospheric CO₂ removal strategies increasingly important within the international climate agenda.”
Among these approaches is ocean alkalinity enhancement, which “does not replace the urgent need to reduce emissions—which remains essential—but it may become necessary to offset residual emissions that are particularly difficult to eliminate and help achieve climate neutrality goals.”
However, although “its effectiveness from a chemical perspective has already been demonstrated, its ecological consequences still need to be fully understood,” says José González.
The experiment carried out at CIM therefore aims to determine whether a strategy capable of helping mitigate climate change is also compatible with preserving marine ecosystems, particularly under global warming conditions.
“In this context, the ocean is a particularly important candidate because of its enormous natural capacity to store carbon and the fundamental role it plays in climate regulation. However, precisely because of the importance and complexity of marine ecosystems, any ocean-based CO₂ removal technique must be evaluated with the utmost scientific rigour before its potential large-scale deployment can be considered. We need to know its actual capacity to remove CO₂ from the atmosphere, how that removal can be accurately measured, what effects it may have on marine ecosystems, and under which conditions it could be environmentally safe and socially acceptable. Mesocosm experiments are a key research tool because they allow real marine communities to be studied under controlled conditions,” says Pablo Serret.
Comparing contrasting marine ecosystems
The results obtained in the Vigo Estuary will be compared with those from similar experiments carried out in Crete as part of the collaboration that CIM has maintained since 2021 with the Hellenic Centre for Marine Research (HCMR).
“Comparing a highly productive coastal ecosystem such as the Galician estuaries with an ultra-oligotrophic environment like the Eastern Mediterranean will allow us to determine whether the response of marine organisms is universal or depends on the environmental characteristics of each region,” explains José González.
In this regard, Pablo Serret emphasises that “this experiment is not an isolated study but part of a coordinated European effort to develop research infrastructures, common protocols and quality standards that enable the scientific assessment of this type of approach. Within the framework of Iriscc, CIM plays a leading role in the development of a new European meta-service for evaluating ocean-based climate mitigation techniques, based on comparable mesocosm experiments conducted in facilities located in Vigo, Crete, Tvärminne-Helsinki and Portugal. The objective is to enable different research groups to assess these techniques using reproducible experimental designs, interoperable datasets and shared quality standards.”
He also points out that “this approach is fully aligned with the European Union’s new policies on nature protection and restoration, which aim not only to conserve biodiversity but also to maintain and restore healthy ecosystem functioning. Measuring community production, respiration and metabolic balance makes it possible to determine whether an intervention affects essential processes such as carbon fixation, oxygen consumption or the flow of matter and energy through the marine food web.”
An internationally recognised research infrastructure
The experiment also highlights the capabilities of CIM’s mesocosm facilities, which are part of the scientific service portfolio of the European Marine Biological Resource Centre (EMBRC-ERIC), of which Ecimat is a member.
Among the few facilities of this kind in Europe, CIM hosts the only outdoor mesocosm installation equipped with a continuous monitoring system and an innovative propeller-based mixing system that reproduces the natural movement of seawater without the use of air bubbling, thereby minimising disturbance to marine organisms while ensuring accurate control of gas exchange between the water and the atmosphere.
The facility has also recently incorporated a new temperature-control system capable of maintaining seawater at a stable temperature three degrees Celsius above ambient conditions, accurately reproducing the ocean warming scenarios projected for the coming decades.
According to Pablo Serret, “the outcome of the experiment carried out in Vigo has been highly positive, both in terms of the scientific results we expect to obtain and the international collaboration it has fostered. It brought together complementary expertise of the highest level at CIM: the technical experience of the Oceanography and Mesocosm Unit, collaboration with leading European research infrastructures such as HCMR and SYKE, and the participation of internationally recognised ocean biogeochemistry groups, including the one at Duke University. This type of collaboration is essential to move from individual experiments towards an integrated European capacity capable of rigorously evaluating potential ocean-based climate change mitigation strategies.”
CIM has been awarded the CIGUS distinction by the Regional Government of Galicia, recognising the quality and impact of its research. Its activities are co-funded by the European Union through the 2021–2027 European Regional Development Fund (ERDF) Programme.
Fonte: DUVI
