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Advanced Taiwan Ocean Prediction System

Tseng, Tsu-Lun - ALL News | 2019-09-18 | Count:62


Title:The potential role of seagrass meadows in ocean acidification buffering and atmospheric CO2 sequestration: insight from the observations at Dongsha Island


Ocean acidification (OA) driven by the uptake of anthropogenic CO2 is likely to adversely affect calcifying organisms across a number of marine environments. However, some environments may be less vulnerable than others. The high productivity of seagrass meadows and their ability to alter seawater carbon chemistry have raised interest in whether these ecosystems may be able to partly mitigate negative effects of OA. In addition, these systems also act as an important sink of blue carbon. In this talk, I will present data collected from Dongsha Island to examine the potential role of seagrass meadows in OA buffering and atmospheric CO2 sequestration. During the study period, the diurnal cycles of carbon chemistry parameters, i.e., dissolved inorganic carbon (DIC), total alkalinity (TA), partial pressure of CO2 (pCO2), and pH, were investigated in two hydrodynamically contrasting seagrass meadows at Dongsha Island in August 2015. The results show that the pH and TA were higher and that the pCO2 was lower in the semi-enclosed inner lagoon (IL) than on the open north shore (NS). The analyses of carbon chemistry parameters vs. dissolved oxygen and TA vs. DIC relationships reveal that the CO2 dynamics was dominated by photosynthesis/respiration (P/R) alone on the NS but by the combined effect of P/R and sedimentary anaerobic pathways in the IL. We suggest that the observed divergent behaviors in carbon chemistry between the two sites could be attributed to differences in hydrodynamic regimes. The less energetic hydrodynamics and longer residence time in the IL would be favourable for the occurrence of sedimentary anaerobic TA generation and the subsequent TA accumulation in the overlying waters. The elevated TA may lead to a pH increase and a pCO2 decrease, thus providing a buffering effect against OA and enhancing atmospheric CO2 sequestration at local scales. The present results demonstrate that hydrodynamic regime may play an important role in regulating biogeochemical processes in seagrass meadows, and thereby modulating their capacities in OA buffering and CO2 uptaking.

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