독도 주변해역에서 화학 양론적(Stoichiometric) 접근을 통한 성장제한 영양염에 대한 고찰

Abstract

In order to determine algal growth limiting nutrients around the Dokdo in the East (Japan) Sea (hereafter, the East Sea) of Korea, water samples were collected in spring and winter from 2006 to 2008 and analyzed for nutrients.Based on the physical properties (temperature and salinity) of this study area, water mass structures were mainly controlled by two major currents.One is southwestward flow along the east coast of Korea called the North Korean Cold Water (NKCW), and the other is northward flow called the East Korean Warm Current (EKWC), which is a branch of the Tsushima Warm Current Water (TWCW). The vertical distributions of nutrients showed a typical pattern of the open ocean, increasing with depth. However, the horizontal distributions (in the depth of 0, 30, and 75 m) were mainly affected by the NKCW rather than by the EKWC even though the front region was formed at the mixing zone of cold water (NKCW) and warm water (EKWC) which was also varied with season. The Stoichiometric approaches (N:P, Si:P, and Si:N ratios) indicated that N (mean 70.2%) was mainly limiting nutrient for algal growth in the surface layer of this study area. But P (39.6%, Dec. 2007) or/and Si (17.1%, Nov. 2006) were also limited nutrients in some area and season. While the traditional approach (Redfield ratio) to determine the limiting nutrient(s) for algal growth suggested this study area was only N-limited environment, Stoichiometric approaches indicated that this study area was not only N-limited but also P-limited or/and Si-limited environment. Therefore, this result suggested that multiple approaches should be needed to get better information on nutrient dynamics in various aquatic environments.