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The effect of elevated CO 2 on the production and respiration of a Sargassum thunbergii community: A mesocosm study
Author(s) -
Punchai Peeraporn,
Ishimatsu Atsushi,
Nishihara Gregory N.
Publication year - 2020
Publication title -
phycological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.438
H-Index - 44
eISSN - 1440-1835
pISSN - 1322-0829
DOI - 10.1111/pre.12414
Subject(s) - mesocosm , carbon dioxide , respiration , photosynthesis , oxygen , ocean acidification , biology , environmental chemistry , ecology , botany , seawater , ecosystem , chemistry , organic chemistry
SUMMARY Approximately one‐third of anthropogenic carbon dioxide is absorbed into the ocean and causes it to become more acidic. The Intergovernmental Panel on Climate Change (IPCC) suggested that the surface ocean pH, by the year 2100, would drop by a further 0.3 and 0.4 pH units under RCP (Representative Concentration Pathway) 6.0 and 8.5 climate scenarios. The macroalgae communities that consisted of Sargassum thunbergii and naturally attached epibionts were exposed to fluctuations of ambient and manipulated pH (0.3–0.4 units below ambient pH). The production and respiration in S. thunbergii communities were calculated from dissolved oxygen time‐series recorded with optical dissolved oxygen sensors. The pH, irradiance, and dissolved oxygen occurred in parallel with diurnal (day/night) patterns. According to net mesocosm production – photosynthetically active radiation (PAR) model, the saturation and compensation PAR, the mean maximum gross mesocosm production ( GMP ), and daily mesocosm respiration were higher in the CO 2 enrichment, than in the ambient condition, while the mean of photosynthetic coefficient was similar. In conclusion, elevated CO 2 stimulated oxygen production and consumption of S. thunbergii communities in the mesocosm. Furthermore, the sensitivity of the GMP of the S. thunbergii community to irradiance was reduced, and achieved maximum production rate at higher PAR. These positive responses to CO 2 enrichment suggest that S. thunbergii communities may thrive in under high CO 2 conditions.