Characteristics of horizontal community distribution and nutrient limitation on growth rate of phytoplankton in Gwangyang Bay, Korea

Abstract

To estimate the effect of potential limiting nutrients for phytoplankton growth and its influences on short-term variations of a winter phytoplankton community structure, we investigated the abiotic and biotic factors of surface and bottom waters at 20 stations of inner and offshore areas in Gwangyang Bay, Korea. Also, several algal bio-assay studies were conducted to identify any additional nutrient effects on phytoplankton assemblage using the surface water for the assay. The dominant species in the bay was diatoms Skeletonema costatum, which occupied more than 70% of total species in the most stations (St.1-16) of the inner bay. According to a cluster and multidimensional scaling (MDS) analysis based on phytoplankton community data from each station, the bay was divided into three groups. The first group included stations from the south-western parts of Myodo lsland, which can be characterized as a semi- enclosed eutrophic area with high phytoplankton abundances. The second group included the most stations from the north-eastern part of Myodo lsland, influenced indirectly by the surface water currents incoming from offshore of the bay. The standing phytoplankton crops were lower than those of the first group. The other cluster was restricted to the samples collected from offshore of the bay. In the bay, silicon (Si) and phosphorus (P) were not a major limiting factor for phytoplankt