A Unique Diel Pattern in Carbonate Chemistry in the Seagrass Meadows of Dongsha Island: The Enhancement of Metabolic Carbonate Dissolution in a Semienclosed Lagoon

In contrast to other seagrass meadows where seawater carbonate chemistry generally shows strong diel variations with higher pH but lower partial pressure of CO2 (pCO2) during the daytime and lower pH but higher pCO2 during nighttime due to the alternation in photosynthesis and respiration, the seagr...

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Bibliographic Details
Published in:Frontiers in Marine Science
Main Authors: Wen-Chen Chou, Lan-Feng Fan, Chang-Chang Yang, Ying-Hsuan Chen, Chin-Chang Hung, Wei-Jen Huang, Yung-Yen Shih, Keryea Soong, Hsiao-Chun Tseng, Gwo-Ching Gong, Hung-Yu Chen, Cheng-Kuan Su
Format: Article in Journal/Newspaper
Language:English
Published: Frontiers Media S.A. 2021
Subjects:
alkalinity production
carbonate dissolution
seagrass
Dongsha Island
blue carbon
ocean acidification
Science
Q
General. Including nature conservation
geographical distribution
QH1-199.5
Ocean acidification
Online Access:https://doi.org/10.3389/fmars.2021.717685
https://doaj.org/article/a0c41b841dd543e494aa3e731ab13392
Description
Summary:In contrast to other seagrass meadows where seawater carbonate chemistry generally shows strong diel variations with higher pH but lower partial pressure of CO2 (pCO2) during the daytime and lower pH but higher pCO2 during nighttime due to the alternation in photosynthesis and respiration, the seagrass meadows of the inner lagoon (IL) on Dongsha Island had a unique diel pattern with extremely high pH and low pCO2 across a diel cycle. We suggest that this distinct diel pattern in pH and pCO2 could be associated with the enhancement of total alkalinity (TA) production coupled to carbonate sediment dissolution in a semienclosed lagoon. The confinement of the IL may hamper water exchange and seagrass detritus export to the adjacent open ocean, which may result in higher organic matter loading to the sediments, and longer residence time of the water in the IL, accompanied by microbial respiration (both aerobic and anaerobic) that may reduce carbonate saturation level to drive carbonate dissolution and thus TA elevation, thereby forming such a unique diel pattern in carbonate chemistry. This finding further highlights the importance of considering TA production through metabolic carbonate dissolution when evaluating the potential of coastal blue carbon ecosystems to buffer ocean acidification and to absorb atmospheric CO2, in particular in a semienclosed setting.

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