Global Comparative Study on Ocean Alkalinity Enhancement Begins in Kiel

Increasing seawater alkalinity by adding an alkaline substance is a promising climate mitigation method that aims to enhance the oceans carbon dioxide (CO₂) storage capacity while simultaneously counteracting local ocean acidification. Ocean alkalinity enhancement (OAE) seeks to accelerate the natural process of rock weathering. A global comparative study is now examining how plankton – the tiny marine organisms at the base of marine food webs – respond to this approach across different marine environments.

Standardized Experiments at 19 Locations Worldwide

The “Ocean Alkalinity Enhancement Pelagic Impact Intercomparison Project (OAEPIIP) is coordinated by Prof. Dr Lennart Bach, a marine biologist at the University of Tasmania, Australia. Nineteen research groups from locations including New Zealand, Kenya, Chile, and Croatia will conduct standardised experiments in enclosed 55 liter containers, known as microcosms, throughout 2025. The microcosms are carefully controlled experimental systems that allow researchers to track changes in plankton community composition and biogeochemical parameters in response to alkalinity enhancement.

GEOMAR’s contribution: Research in the Baltic Sea and in Tropical Waters

GEOMAR is contributing to this project with two studies in contrasting environments: Dr Giulia Faucher, a researcher in the Biogeochemical Processes working group, will examine OAE impact on a temperate plankton community from Eckernförde Bay in the Baltic Sea. For this purpose, she started the experiment on 7 March 2025 by filling the microcosms aboard the research cutter LITTORINA at the Boknis Eck time-series station. “The containers used, the way they are filled, the way the alkalinity is added and the measurements taken – all of this is standardised to ensure comparability across the studies,” says Giulia Faucher.

Her colleague in the same research group, Dr Leila Kittu, will conduct the same experiment in tropical waters off Kenya from May onwards. To facilitate this, she has established a new collaboration between GEOMAR, the Kenya Marine Fisheries Research Institute (KMFRI), and the Technical University of Mombasa (TUM).

Why Standardization Matters in OAE Research

OAEPIIP is the first globally coordinated study on ocean alkalinity enhancement. “These standardized experiments enable us to assess its ecological effects across diverse environmental conditions, from temperate to tropical waters, from nutrient-rich to nutrient-poor regions” says Giulia Faucher. The results will contribute to a comprehensive meta-analysis, offering new insights into potential ecological impacts of ocean alkalinity enhancement — critical information for policymakers considering large-scale deployment of this approach as part of climate change mitigation strategies.

About: Ocean Alkalinity Enhancement

Ocean alkalinity enhancement mimics natural rock weathering processes that gradually increase ocean alkalinity over geological timescales. However, since human-caused CO₂ emissions occur approximately a hundred times faster than these natural weathering processes, OAE accelerates this mechanism through the direct addition of alkaline minerals to seawater. This addition increases seawater's pH and carbonate ion concentration, enhancing its capacity to chemically bind more CO₂. This enhanced carbon sequestration pathway effectively accelerates a natural carbon sink to help counterbalance rapid human-induced CO₂ emissions. While OAE is primarily aimed at increasing CO₂ uptake and storage, the resulting increase in pH could simultaneously provide a buffering effect against ocean acidification at local scales where alkalinity is added.