MEPS 186:75-86 (1999)  -  doi:10.3354/meps186075

Spring distribution of diatom assemblages in the East China Sea

Kuo-Ping Chiang1,*, Ying-Tun Chen1, Gwo-Ching Gong2

1Institute of Fishery Science and 2Department of Oceanography, National Taiwan Ocean University, Keelung 202-24, Taiwan, ROC

ABSTRACT: The distribution of diatom assemblages in the East China Sea in late spring was investigated in relation to hydrographical characteristics. Using principal component analyses, 3 water types and 4 diatom assemblages were defined. The distribution pattern of water types showed a 2-layer structure. The nutrient-depleted Surface Water Type forms a layer above the nutrient-laden Mid-Layer Water Type. In addition, the low-salinity eutrophic Coastal Water Type was found near the Changjiang river plume. In general, the distribution of diatom assemblages matches that of water types. The Upwelled Assemblage and the Coastal Assemblage existed respectively in the upwelled Subsurface Kuroshio Water (the Mid-Layer Water Type) and the Changjiang river plume (the Coastal Water Type). A Background Assemblage with low standing stock was found over the entire study area in both the Surface Water Type (nutrient limited) and the Mid-Layer Water Type (light limited). The Shelf-Break Assemblage was observed near the shelf break, where variations in physical or chemical environments were insignificant. This probably resulted from an upwelling event that had not previously been observed. Our results indicate that a widespread Background Assemblage is the basic diatom distribution pattern in the East China Sea. At locations where a nutrient source becomes available, the Background Assemblage will change into a new assemblage such as the Upwelled Assemblage or the Coastal Assemblage.

KEY WORDS: Background assemblage · Diatom assemblage · East China Sea · Upwelling · Kuroshio

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