Instability of the turbidity maximum in the macrotidal Geum River estuary, western Korea

Abstract

In the low-salinity area of many macrotidal estuaries, through the combination of tidal pumping and estuarine circulation, an estuarine turbidity maximum (ETM) develops providing favorable conditions for various organisms. To investigate ecological roles of the ETM in East Asian estuaries, we conducted seasonal observations in the Geum (or Keum) River estuary, one of the representative macrotidal estuaries flowing into the Yellow Sea, from 2007 to 2008. The estuary was frequently filled with high-salinity ([10 PSU) and low-turbidity (\100 NTU) water under small or no freshwater discharge from a dam (ca. 8 km upstream from the river mouth). Brackish water was, however, completely pushed out of the estuary within a few hours after an intensive discharge in summer. Chlorophyll a (up to 50 lg l -1 ) and pheophytin (up to 80 lg l -1 ) were concentrated in a low-salinity (\1 PSU) and high-turbidity (up to 1000 NTU) area, indicating that the intensive discharge transported both living phytoplankton and resuspended detritus into the area. In contrast, a phytoplankton bloom (chlorophyll a, up to 100 lg l -1 ) was observed at low salinities under little discharge in winter. The present study demonstrated an absence of the ETM suitable for estuarine-dependent organisms from the present Geum River estuary, indicating potential importance of adequate control of freshwater discharge for the formation and maintenance of the ETM.

Year-round accumulation of particulate organic matter in the estuarine turbidity maximum: comparative observations in three macrotidal estuaries (Chikugo, Midori, and Kuma Rivers), southwestern Japan

“…Since large-scale coastal developments are prevailing in the Ariake Sea as well as on the Eurasian continent (cf. Sato 2006;Suzuki et al 2010), both relict and main populations will face increasing difficulties for survival owing to their strong dependence on the estuarine environment, specifically the ETM.…”

Changes in Water Quality After the Construction of an Estuary Dam in the Geum River Estuary Dam System, Korea

“…A number of studies were conducted on the quality of the upstream impounded water to address various processes, including hydrology (Wright and Worrall, 2001), residence time (Rueda, Moreno-Ostos, and Armengol, 2006;Søballe and Kimmel, 1987), nutrients and primary production (Jones and Knowlton, 2005), and watersediment interactions (Mhamdi, Aleya, and Devaux, 1994;Zhijing, Xinbao, and Nanshan, 2011). Many studies were also conducted on the water quality conditions downstream of dams (e.g., Azevedo, Duarte, and Bordalo, 2008;Jeong et al, 2005;Lee and Yang, 1997;Suzuki et al, 2010;Warnken and Santschi, 2004;Yang et al, 1999). However, there have been relatively fewer studies that address the upstream and downstream sides of dams simultaneously, despite the importance of the quantity and quality of the discharge through dams on the water downstream of dams (Friedl and Wüest, 2002;Rosenberg et al, 1997).…”

“…Since the dam construction, several studies have been conducted to examine changes in estuarine types and sediment transport (Kim, Choi, and Lee, 2006;Lee et al, 1999), estuarine water quality (Kim and Kang, 2002;Jeong et al, 2005;Lee and Yang, 1997;Suzuki et al, 2010;Yang et al, 1999), reservoir water quality (Rim, Shin, and Cho, 2000;Shin and Cho, 2000), and reservoir sediment chemistry (Chung and Hwang, 2002;Hwang, Chung, and Chung, 2001;Kim and Lim, 1997;Lee, Lee, and Park, 2005). None of these studies, however, considered the upstream reservoir and downstream estuarine sides of the dam together, although the necessity of the information on the reservoir water in assessing the estuarine water quality was noted (Jeong et al, 2005;Lee and Yang, 1997).…”

Response of the turbidity maximum zone in the Yangtze River Estuary due to human activities during the dry season

“…This ability of estuaries to remove or retain material in solution and suspension has important implications for environmental issues, such as eutrophication (Gebhardt et al 2005). The TMZ serves as a nursery area for some migratory fish, such as Coilia mystus in the Yangtze River Estuary and the oxygen level in the estuary closely tracks changes to the TMZ (Liu and Xian 2009;Talke et al 2009), which have substantial impacts on the abundance and distribution of fish (Islam et al 2006;Suzuki et al 2009;Garnier et al 2010). The TMZ is apparent throughout the year but is a dynamic section of the estuary.…”