Enhanced benthic weathering (EBW) is a promising carbon dioxide removal (CDR) strategy. In the Baltic Sea, seasonally hypoxic bottom waters are considered ideal settings for EBW. Addition of alkaline minerals (calcite and dunite) to the seafloor accelerates weathering, releases alkalinity to the water column and fosters CDR. However, feedbacks of microbial metabolisms currently remain unknown.
In the first phase of RETAKE I, the focus was on identifying which alkaline mineral (i.e. calcite or dunite) would be more favorable and efficient for CDR when artificially added to organic-rich Baltic Sea sediments. To assess the carbon dioxide uptake potential, related to enhanced weathering of calcite or dunite (i) laboratory sediment core incubations exposed to fully oxic or low oxygen bottom water conditions as well as (ii) long-term benthocosm experiments were conducted (cf. Fuhr et al. 2024, Fuhr et al. 2025, Dale et al. 2024). One of the major findings of these experiments was that calcite had an up to 10-fold higher carbon dioxide uptake efficiency than dunite (Fuhr et al. 2025).
To assess the effects that EBW has on the benthic microbial community and its metabolisms, 16S amplicon sequencing, CARD-FISH, cell counts as well as metagenomic and transcriptomic analyses are combined. Based on RNA-profiling the shifted microbial communities showed no distinct pattern in relation to alkaline mineral additions when exposed to fully oxic bottom water conditions (Fuhr et al. 2024). In contrast, later work on sediment core incubations under low oxygen conditions clearly demonstrated that a distinct shift within the microbial consortium was apparent (as indicated by metagenomics and transcriptomics) correlating with calcite addition and low oxygen bottom water conditions - further promoting alkalinity production (B盲hrle et al. in review)
Work on benthocosms is currently still be evaluated with respect to impacts of EBW on microbial community compositions and functionality.
RETAKE I - Team
Principal Investigators
(Biogeochemistry) (Lead: 2021-2023)
Mirjam Perner (Geomicrobiology)
Andy Dale (Biogeochemistry)
Doctoral candidates
Michael Fuhr (Biogeochemistry) (2021-2024)
Isabel Diercks (Geomicrobiology) (09/2021-05/2023)
Rebecca B盲hrle (Geomcirobiology) (2022-2024)
Associated
Frank Ohnem眉ller (Lime & Morter Industry)
Frank Melzner (Invertebrates)
In the first phase the experimental data and predictions from complex numerical models exhibited considerable discrepancies for the CDR potential. This Is likely due to deviations in bottom water mineral saturation, redox conditions and microbial community succession related to incubation of sediment cores under laboratory conditions. Consequently, experiments under in situ field conditions were necessary.
Experiments with the BIGO (Biogeochemical Observatory) Lander systems will be conducted in regions of the Baltic Sea that are exposed to seasonal hypoxia (Boknis Eck, Eckernf枚rde Bight) and permanent anoxic (Gotland Basin) bottom water conditions. The BIGO Systems contain two benthic chambers, various sensors and the ability to collect and fix subsamples in situ during the experiment from the chamber waters. A newly developed calcite addition system will enable injection of calcite to one of the chambers while the other benthic chamber will serve as control and remain unamended. This will enable us to monitor chemical and microbial changes at the seafloor after calcite addition over a period of three weeks. At the end of the BIGO in situ experiments the sediments will be brought up for further microbial and geochemical analyses.
![[Translate to English:] BIGO](/fileadmin/_processed_/c/e/csm_IMG_1354_71fd4cab9a.jpg)
Recovery of BIGO Lander System with the MzB HELIOS
For these BIGO experiments three research cruises are envisioned:
(L25-02b, MzB Helmsand, MzB HELIOS) - February 2025 (chief scientist: Mirjam Perner)
ALKOR (July 2025) (chief scientist: Andy Dale)
ALKOR Spring 2026 (chief scientist: Nicole Adam-Beyer)
RETAKE II - Team
Principal Investigators
Mirjam Perner (Geomicrobiology)
Andy Dale (Biogeochemistry)
PostDoc
Michael Fuhr (Biogeochemistry) (2024-2025)
Scientist
Stefanie B枚hnke-Brandt
Katja Laufer-Meiser
Nicole Adam-Beyer
Associated
Frank Ohnem眉ller (Lime & Morter Industry)
Frank Melzner (Invertebrates)
RETAKE II
Perner, M. et al. (2025) Calcite addition to surface sediments as a CO2 removal strategy in seasonal hypoxic coastal waters promotes cable bacteria and alters the biogeochemical cycle. [Talk] FEMS Microbiol. Milan, Italy
Fuhr, M., Wallmann, K., Perner, M. & A. Dale (2025). In situ incubation experiments to assess the potential for calcite based ocean alkalinity enhancement. [Talk] College de Li猫ge
B盲hrle, R. J., Baaske, R., Bornemann, T. L. V., Fuhr, M., B枚hnke, S., Soares, A., Dale, A. W., Probst, A. J., Geilert, S. und Perner, M. (in review) ISME Communications: New Developments in Microbial Ecology
Fuhr, M., Dale, A. W. , Wallmann, K. , B盲hrle, R. J., Kalapurakkal, H. T., Sommer, S., Spiegel, T., Dobashi, R., Buchholz, B., Schmidt, M., Perner, M. und Geilert, S. (2025) Communications Earth & Environment, 8 . Art.Nr. 106 (2025). DOI .
Perner, M. (2025) 黑料视频 Helmholtz Centre for Ocean Research Kiel, 6 pp.
Perner, M. , B盲hrle, R. J., Baaske, R., Bornemann, T. L. V., Fuhr, M., B枚hnke, S., Soares, A., Dale, A. W. , Probst, A. J. und Geilert, S. (2025) [Talk] In: Annual Conference of the Association for General and Applied Microbiology, 23.-26.03.2025, Bochum, Germany.
Dale, A. W. , Geilert, S. , Diercks, I., Fuhr, M., Perner, M. , Scholz, F. und Wallmann, K. (2024) Communications Earth & Environment, 5 . Art.Nr. 452. DOI .
B盲hrle, R., B枚hnke-Brandt, R., Fuhr, M., Dale, A. and M. Perner (2024). Reactions of the microbial community in benthic alkalinity enhancement experiments. [Talk] In: Annual Conference of the Association for General and Applied Microbiology. VAAM, 02.-05.06.2024, W眉rzburg, Germany.
RETAKE I
Fuhr, M., Wallmann, K., Dale, A. W. , Diercks, I., Kalapurakkal, H. T., Schmidt, M. , Sommer, S., B枚hnke, S., Perner, M.und Geilert, S.(2023) Frontiers in Climate, 5 . Art.Nr. 1245580. DOI .
Diercks, I.,Geilert, S., B枚hnke-Brandt, S., Dale, A.W., Fuhr, M., Perner, M. (2022). Interactions between microbial activity and enhanced benthic weathering of carbonate and olivine in the Baltic Sea. ePoster auf der VAAM Jahrestagung 2022
Diercks, I.,Geilert, S., Dale, A.W., Fuhr, M. and Perner, M. (2022). Interactions between microbial activity and enhanced benthic weathering in the Baltic Sea to analyse the potential, benefits and risks of a marine CDR strategy. YOUMARES13, Berlin.
