Understanding seasonal variation of the source of particulate organic matter in relationship with plankton community in the estuary of Sumjin River, Korea

Abstract

The estuary is not only physically very dynamic environment but also one of the most productive natural habitats. In the aspects of carbon cycle, it is one of key boundaries of different sources of organic carbons are transported, deposit, and recycled with high biological activities. Therefore, we bi-monthly examined the biochemical compositions (i.e. Chl-a, POC/N and lipid biomarkers) of suspended particles (> 0.7μm) to understand the seasonal changes of the relative contribution of different source of organic carbon comparing with plankton community and other water parameters (nutrients, temperature, salinity, rainfall, etc) in the drowned river valley estuary of Sumjin River, Korea, for a year 2010. The unusual winter-bloom of Skeletonema costatum occurred in January (Chl-a: 12.2 μg/L) with the low C:N ratio (≈ 6.0). However, the C:N ratios (> 10) was high in the summer and fall with the same level of POC as that in winter. It means that the other sources of organic carbon (i.e. terrestrial and urban source) could be significantly contributed during the summer and fall. According to the result of lipid biomarkers, the relative abundance of 22:6(n-3), used as a marker for dinoflagellate, was seasonally varied, especially well corresponding with the abundance of Dinophyceae. The results of this study will provide valuable information to understand the seasonal variation of the reit, and recycled with high biological activities.