Ocean acidification - effects on benthic microbial diversity and function
The world’s oceans take up roughly 30% of the current anthropogenic CO2 emissions. The increased dilution of CO2 in seawater results in a decrease of pH as well as a dilution of carbonates. The dramatic effects, especially on calcifying plankton, can already be observed globally. Still, very little is known about the consequences for microbial communities, which play a central role in marine nutrient cycling.
Within the national research project BIOACID, effects of increased CO2 levels on benthic microbial diversity, biomass, community composition, abundance as well as functional changes in the ecosystem, will be investigated with a toolkit of diverse molecular techniques (e.g. T-RFLP, ARISA, 16S rRNA, and functional gene sequencing, FISH, qPCR, metagenomics). Long-term effects are projected by the comparative study of sediment samples naturally exposed to different CO2 concentrations, thereby mimicking future CO2 levels. Furthermore, community-shifts as well as ecosystem resistance and resilience, are experimentally investigated as a function of pH, temperature, and CO2 variations, using flow-through reactors as sedimentary mesocosms.
In addition, we study the effects of high CO2 levels, as reached at hydrothermal vents at the deep seafloor. Interest in the study of such systems is recently increasing, as they represent a natural analogue to potential leaks from man-made CO2 deposits in deeper sediment layers. Such procedures for carbon capture and storage have been suggested as a possible way out to reduce CO2 emissions to the atmosphere. From measurements and samples that were taken along a natural occurring pH gradient at a hydrothermal vent off Japan, it could be concluded that low pH-levels due to high CO2 levels result in significant changes in the bacterial community structure, reduced biodiversity of the megafauna, and generally increased spatial heterogeneity of the benthic communities.
Contact: A. Boetius, A. Ramette
Literature:
Inagaki, F., Kuypers, M.M., Tsunogai, U., Ishibashi, J., Nakamura, K., Treude, T., Ohkubo, S., Nakaseama, M., Gena, K., Chiba, H., Hirayama, H., Nunoura, T., Takai, K., Jørgensen, B.B., Horikoshi, K. & A. Boetius (2006). Microbial community in a sediment-hosted CO2 lake of the southern Okinawa Trough hydrothermal system. Proceedings of the National Academy of Sciences 103 (38): 13899-13900.