황해에서 크기별 식물플랑크톤 군집의 시공간적 변화

Abstract

We investigated phytoplankton biomass and composition to understand latitudinal differences of size-fractionated phytoplankton structure before (spring) and after (summer) formation of bottom cold waters in the Yellow Sea in 2010 and 2011. The surveyed stations were selected along lines from coastal to off-shore waters (124.5 and 125.5°E) located at two latitudes (34.5 and 36°N). Based on the thermocline depth in summer, two depth strata (0-20m, 20-80m) were considered for analysis of latitudinal differences of phytoplankton community. Water temperature in the surface waters differed before and after formation of bottom cold waters, whereas cold waters (<10℃) in the bottom layer existed consistently. Total chl-a concentration of surface waters, representing the standing crop of phytoplankton, was higher in spring (Ave. 2.20 μg L-1) than in summer (Ave. 1.06 μg L-1) at both latitudes. Micro-sized (>20 μm) phytoplankton dominated numerically at the north and south latitudes in spring. Small centric diatoms were abundant at the north latitude, while nanoflagellates predominated at the south latitude in summer. In the bottom waters, total chl-a concentration was higher in summer (Ave. 1.12 μg L-1) than in spring (Ave. 0.67 μg L-1). Nanoflagellates dominated the total chl-a concentration of bottom cold waters at both latitudes in summer, whereas Paralia sulcata and Skeletonema costa