The use of ocean alkalinity enhancement (OAE) as a negative emission technology has the potential to reduce atmospheric carbon dioxide and achieve carbon neutrality. However, we still don't fully understand the side effects of OAE. To gain a better understanding, experiments were conducted in Daya Bay, Shenzhen, China, involving the addition of magnesium hydroxide in 50,000-liter mesocosms and 50-liter incubators. The study continuously observed the structure of the prokaryotic community over time across different treatments. The results showed that the prokaryotic community structures were largely similar between different treatments within the same batch of experiments. In the 50,000-liter mesocosms (Experiment 1 and Experiment 2), significant differences in the diversity and richness of prokaryotic communities were observed between experimental and control groups. However, in the 50-liter incubators, no significant differences in diversity and richness were found, which is possibily due to the bottle effect. These results suggest that OAE has minimal impact on the structure of coastal prokaryotic communities, and larger volume culture systems are more suitable for investigating the side effects of OAE on microbial communities. This study provides additional references for future investigations into the ecological impacts of OAE.

ocean alkalinity enhancement,magnesium hydroxide,side effect,prokaryotic community,bottle effect