The Diel and Seasonal Heterogeneity of Carbonate Chemistry and Dissolved Oxygen in Three Types of Macroalgal Habitats

• Published in: Frontiers in Marine Science
• Main Authors: Huiru Li, Hanbi Moon, Eun Ju Kang, Ja-Myung Kim, Miok Kim, Kitack Lee, Cheol-Woo Kwak, Haryun Kim, Il-Nam Kim, Ki Yeol Park, Young Kweon Lee, Ji Woong Jin, Matthew S. Edwards, Ju-Hyoung Kim
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2022
• Subjects: biogeochemical interaction; carbonate chemistry; dissolved oxygen; diel fluctuation; macroalgal habitat; Science; Q; General. Including nature conservation; geographical distribution; QH1-199.5; Ocean acidification
• Online Access: https://doi.org/10.3389/fmars.2022.857153; https://doaj.org/article/441e0c9a023a4e64a51a76acbed8a5ba

As concerns about ocean acidification continue to grow, the importance of macroalgal communities in buffering coastal seawater biogeochemistry through their metabolisms is gaining more attention. However, studies on diel and seasonal fluctuations in seawater chemistry within these communities are still rare. Here, we characterized the spatial and temporal heterogeneity in diel and seasonal dynamics of seawater carbonate chemistry and dissolved oxygen (DO) in three types of macroalgal habitats (UAM: ulvoid algal mat dominated, TAM: turf algal mat dominated, and SC: Sargassum horneri and coralline algae dominated). Our results show that diel fluctuations in carbonate parameters and DO varied significantly among habitat types and seasons due to differences in their biological metabolisms (photosynthesis and calcification) and each site’s hydrological characteristics. Specifically, carbonate parameters were most affected by biological metabolisms at the SC site, and by environmental variables at the UAM site. Also, we demonstrate that macroalgal communities reduced ocean acidification conditions when ocean temperatures supported photosynthesis and thereby the absorption of dissolved inorganic carbon. However, once temperatures exceeded the optimum ranges for macroalgae, respiration within these communities exceeded photosynthesis and increased CO2 concentrations, thereby exacerbating ocean acidification conditions. We conclude that the seawater carbonate chemistry is strongly influenced by the metabolisms of the dominant macroalgae within these different habitat types, which may, in turn, alter their buffering capacity against ocean acidification.