Estuaries, where freshwater from a river mixes with saltwater from the ocean, are highly susceptible to rapid decreases in pH (acidification) and aragonite saturation state (Ωarg) due to the poorly buffered water delivered by river water inputs. Additionally, anthropogenic activities, such as land use changes and nutrient pollution, can further lower the Ωarg in estuaries. However, acidification in eutrophic estuaries is not well understood. Here, we investigated Ωarg changes in three contrasting Korean estuary systems in summer; Han River (HR), an open estuary, and the Guem River (GR) and Youngsan River (YSR), closed estuaries where are enclosed by dam at the river mouth. Our findings showed that the mean Ωarg in HR, GR, and YSR estuaries are 1.6±0.7, 1.9±0.6, and 2.5±0.6, respectively. It is interesting that open estuary is lower than closed estuaries. During the summer, the river waters inputs delivered poorly buffered water to the upper estuaries, resulting in low Ωarg. However, seawater mixing toward Yellow Sea, with relatively higher, buffered the decrease in Ωarg at the lower estuaries. Our result suggest that river water inputs of low-to-intermediate total alkalinity can expand estuarine acidification zone, and the decrease in Ωarg is expected to accelerate over time in regions where the buffering capacity decrease. This low Ωarg can have significant impacts on the health and survival of estuarine organisms that rely on calcium carbonate structures. 

Primary Presenter: Yujeong Choi, Research Institute for Basic Sciences Chonnam National University (meridachoi@gmail.com)

Authors:

Yujeong Choi, Research Institute for Basic Sciences, Chonnam National University  (meridachoi@gmail.com)

Tae-Hoon Kim, Chonnam National University  (esutaikim@gmail.com)

Min-Young Lee, Chonnam National University  (dlalsdud2005@naver.com)

Gyuri Kim, Chonnam National University  (tagu0715@naver.com)

Hyebin Kim, Chonnam National University  (berryk1231@naver.com)