DISTRIBUTION OF DIATOMS IN THE SURFICIAL SEDIMENTS OF THE MANGYUNG-DONGJIN TIDAL FLAT, WEST-COAST OF KOREA (EASTERN YELLOW SEA)

The relationship between the distribution of benthic diatoms and sedim ent characteristics of the Mangyung-Dongjin tidal flat on the west coa st of Korea was investigated during June and July 1988. Diatoms were c ollected from the upper 5 mm of sediments at 60 sites along eight tran sect lines running perpendicular to the shore line. Of the 371 taxa en countered in the study area, 88% were pennate diatoms. Genera represen ted by the greatest number of species were Navicula, Nitzschia, Amphor a, Cocconeis, Fragilaria and Achnanthes. The most abundant spe species were Paralia sulcata, Navicula sp. #1, N. arenaria and Cymatosira bel gica; all were broadly distributed across the tidal flats. The 60 site s could be assigned to eight clusters with respect to similarity in sp ecies composition. Discriminant analysis showed that separation cluste r was primarily related to the mean grain size of the sediment. The sp ecies could not be separated into groups based on similarities in occu rrence; a high degree of spatial overlap was observed. The preferences of the more abundant species for grain size were, therefore, analysed by plotting numerical abundance against mean grain size. There were a t least four patterns: species groups could be associated with fine-gr ained sediments, those of intermediate size and coarser sediments and the last group showed no discernible pattern.