Reporting time: Tuesday, November 5, 2024 14:30-16:00
Reporting location: C302 (Tencent meeting number: 147-698-066)
Report title: Dynamic changes of ocean acidity, CO2 flux and carbon metabolism rate in Weizhou Island coral reef: a buoy-based observational study
Speaker: Associate Researcher Xu Dong (Third Institute of Oceanography, Ministry of Natural Resources)
Brief introduction of the speaker:
Xu Dong, master's tutor, is currently an associate researcher in the Marine Ecological Environment Early Warning and Monitoring Research Office of the Third Institute of Oceanography of the Ministry of Natural Resources, a member of the innovation team of ocean-atmospheric biogeochemical cycle and its climate effects, and a research backbone of the Beibu Gulf and West Coast Field Scientific Observation and Research Station of the Ministry of Natural Resources. Mainly engaged in ocean acidification and carbon cycle research. In recent years, certain progress has been made in the observation, formation mechanism and evolution trend research of coral reef ocean acidification. The relevant results are reported by the first and corresponding authors in Journal of Geophysical Research: Oceans, Journal of Geophysical Research: Biogeosciences, Journal of Marine Systems, Estuarine, Coastal and Shelf Science Published in mainstream international journals.
Summary of the report:
Coral reefs demonstrate how environmental changes affect their health through two key processes: net calcification (balance between reef building and dissolution) and net production (balance between organism growth and decomposition). In order to better understand the relationship between these processes, we used the mooring buoy method to measure the seawater on the coral reef of Weizhou Island Synchronous high-frequency measurements of pH, aragonite saturation state, carbon dioxide flux, and carbon metabolism rate were performed for 37 consecutive days. The study found that net calcification and net production of coral reef ecosystems are closely related and persist even in the absence of light. This association can be explained by how coral reef carbonate deposits respond to changes in water chemistry. Our study revealed that the coral reefs at the study sites were mostly in an ecosystem-scale net-dissolved state and that the organisms consumed more energy than they produced (i.e., heterotrophic state). This suggests that coral reef ecosystems are more prone to net dissolution when organisms decompose more than they grow. This is particularly evident for reef bodies with low live hard coral cover. When the reef body dissolves, alkalinity is released to balance the increase in acidity caused by biological respiration. Interestingly, we also found that biological respiration, rather than reef calcification, was the main source of CO ₂ emissions to the atmosphere from reefs at the study site.
