Ocean liming in the oligotrophic Eastern Mediterranean: impact on the planktonic microbial food web
- 1Hellenic Centre for Marine Research, Insitute of Oceanography, Heraklion, Greece (vpitta@hcmr.gr)
- 2University of Crete, Department of Biology, Crete, Greece
- 3Centro de Investigación Mariña da Universidade de Vigo, Estación de Ciencias Mariñas de Toralla (ECIMAT), Vigo, Spain
- 4Centro de Investigación Mariña da Universidade de Vigo, Departamento de Ecoloxía e Bioloxía Animal, Vigo, Spain
- 5Politecnico di Milano, DICA-Dept of Civil and Environmental Engineering, Piazza Leonardo da Vinci, 32, 20133 Milano, Italy
- 6Politecnico di Milano, DCMC-Dept of Chemistry, Materials and Chemical Engineering, Via L. Mancinelli 7, 20131, Milano, Italy
- 7University of Milano-Bicocca, DISAT-Dept of Earth and Environmental Sciences, Piazza della Scienza 4, 20126, Milano, Italy
- 8Institut de Ciencies del Mar – CSIC, Barcelona, Spain
- 9Centro para el Estudio de Sistemas Marinos (CESIMAR-CONICET), Puerto Madryn, Chubut, Argentina
- 10Norwegian University of Science and Technology (NINU), Department of Biology, Trondhjem Biological Station, Norway
Ocean Alkalinity Enhancement (OAE) allows for active removal of atmospheric CO2, therefore is considered as one of the most promising Carbon Dioxide Removal (CDR) technologies. OAE could be obtained by discharging alkaline material in the wake of ships, however very little is known on potential negative effects on marine communities. We report here the first study focusing on the response of the entire pelagic microbial food web to the addition of calcium hydroxide in real oligotrophic conditions. In a mesocosm experiment performed at the CretaCosmos facility in Crete, Greece, in May-June 2023, we tested the response of the eastern Mediterranean oligotrophic waters to two different treatments of calcium hydroxide slurry addition (SL; High and Low concentrations, three replicate mesocosms each), while three more mesocosms served as Controls (no addition). Mesocosms, filled with natural coastal seawater, were treated with slurry on days 1, 3, 5, 7, 9, 11 to simulate the chronic disturbance, expected from repeated discharge of SL from ships; while the possible precipitation of carbonate crystals was assessed by putting a sediment trap at the bottom of each mesocosm. The carbonate-equilibrium and dissolution-kinetics were monitored by measuring temperature, solution-conductivity, and changes in pH. Photosynthetically-Active-Radiation and visible light were monitored by sensors in each mesocosm. Plankton productions (bacterial, viral, secondary) as well as community composition of all plankton groups from viruses to copepods were assessed by optical microscopy, flow cytometry and metagenomics; chlorophyll was also measured. Although an important alteration of pH was observed in the High lime addition, only heterotrophic bacteria production was found to be negatively affected and only in the second half of the experiment. The rest of the plankton groups presented different patterns and not a clear response to the lime addition. This first attempt to study the effect of lime addition on the complex pelagic food web will serve as a first step to an extensive testing needed before any application of ocean liming at a large scale.
How to cite: Pitta, P., Magiopoulos, I., Romano, F., Tsiola, A., Chantzaras, C., Gonzalez, J., Serret, P., Valsecchi, S., Varliero, S., Basso, D., Azzellino, A., Barbaccia, E., Traboni, C., Nocera, A. C., Courboules, J., and Tsapakis, M.: Ocean liming in the oligotrophic Eastern Mediterranean: impact on the planktonic microbial food web, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18538, https://doi.org/10.5194/egusphere-egu24-18538, 2024.
