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Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
Over the coming weeks, international researchers led by the GEOMAR Helmholtz Centre for Ocean Research Kiel will conduct an experiment in closed marine tanks on the coast of Gran Canaria to investigate the effect of various methods of ocean alkalisation on the marine ecosystem. In so-called mesocosms, which are similar to oversized test tubes, natural ecosystems can be observed under controlled conditions. This study will be the first to systematically compare two approaches: adding already dissolved minerals and introducing finely ground rock into seawater.
Mimicking natural rock weathering to increase ocean alkalinity could help the ocean absorb more CO2 from the atmosphere while simultaneously buffering acidification. This approach is known as Ocean Alkalinity Enhancement (OAE). It is one of the ocean-based methods of carbon dioxide removal (CDR). While such approaches cannot replace the urgent need for a rapid reduction in greenhouse gas emissions, they are being discussed as a means of offsetting unavoidable residual emissions. OAE involves adding minerals, such as silicate or lime, to seawater to make it more alkaline. A key question for researchers is how marine organisms would respond to such interventions in seawater chemistry.
To investigate this, a field experiment is now beginning off the coast of Gran Canaria. The experiment is led by Prof. Dr Ulf Riebesell, Professor of Biological Oceanography at the GEOMAR Helmholtz Centre for Ocean Research Kiel. Marine biogeochemist Dr Kai Schulz, a visiting researcher from Southern Cross University (Australia), will be providing on-site direction. For the first time, two approaches are being compared systematically: adding already dissolved minerals and introducing finely ground rock into seawater.
Natural and Accelerated Rock Weathering
In the long term, nature binds carbon dioxide through the process of rock weathering. Minerals are transported into the ocean via rivers and chemically store CO2 in dissolved form. However, this natural process takes millennia, which is far too long to mitigate human-induced climate change significantly in the coming decades. For this reason, researchers worldwide are investigating whether this process can be accelerated. In addition to the potential for long-term CO2 storage, ocean alkalinity enhancement could have an added benefit: it could counteract the increasing acidification of seawater caused by the absorption of large amounts of CO2 emissions.
Mesocosms as a Field Laboratory
For the Gran Canaria experiment, researchers are using Kiel mesocosms, which are 3.5-metre-long plastic tubes suspended in the sea on fixed frames. Within them, natural communities can be observed under controlled conditions, much like in oversized test tubes. The 12 mesocosms are currently being set up and filled. The crucial intervention will take place on 19 and 20 September, when minerals will be added. The aim is to compare the effects of dissolved alkalinity versus rock powder on the ecosystem.
Comparative Experiments in North and South
The current experiment builds on a series of field studies on OAE conducted in Gran Canaria in 2021, off the coast of Bergen (Norway) in 2022, on Heligoland in 2023, and in the Kiel Fjord (Germany) last year. In the Kiel study, finely ground rock was used for the first time instead of previously dissolved minerals. Significantly stronger effects on zooplankton were observed under certain conditions, particularly at greatly increased concentrations. It remains unclear whether these differences are due to the particles not yet being fully dissolved, which could directly influence organisms within the first few hours or days.
Dr Kai Schulz: “The aim of this experiment is to find out whether the particles themselves have an additional effect on the ecosystem or if the observed effects are solely due to the increased alkalinity of the water.” The scientific director, Prof Dr Ulf Riebesell, explains why this is important: “Effects on zooplankton would also propagate to animals higher up the food chain. Only by fully understanding these mechanisms can we realistically assess the potential risks and benefits of ocean alkalinity enhancement.”
https://www.geomar.de/en/news/article/neue-mesokosmen-studie-auf-gran-canaria Images for Download
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Mesocosms are enclosed marine containers in which international researchers are investigating the ef ...
Source: Michael Sswat, GEOMAR
Copyright: Michael Sswat, GEOMAR
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Mesocosms are enclosed marine containers in which international researchers are investigating the ef ...
Source: Michael Sswat, GEOMAR
Copyright: Michael Sswat, GEOMAR
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