| The degradation of organic matter along the water column is mediated by enzymes released into the environment by planktonic organisms. Variations in extracellular enzymes activity reflect the trophic status (quality and quantity of organic matter) of the environment. Horizontal and vertical distribution of nine kinds of extracellular enzyme activities in seawater of 42 stations, one transects C (three stations located in the SYS Cold Water Mass), and one day and/or night continuous observing station MT1 in the Yellow Sea (YS) and the East China Sea (ECS) on the cruises from 12nd July to 1st August in 2013 were investigated to evaluate the distribution and the degradation of organic matter. The mean extracellular enzymes activity in the surface water differed, the ranking of them with largest to smallest: alkaline phosphatase (APA), aminopeptidase (AMP), lipase (LIP), cellulase (CEL), chitinase (CHI), d-D-glucosidase (AGLU), d-D-glucosidase (BGLU), d-D-galactosidase (BGAL), xylosidase (XYL). The vertical activity profiles of transact C showed that APA, AMP, LIP, BGLU and AGLU reached the highest values in 10-20 m water, whereas CEL and XYL showed higher activities in surface water than the bottom water. Significant differences in enzyme activity between different parts of the studied area were demonstrated, with higher values in the seawater zone and lower values in the freshwater zone, which were influenced by Yangtze Diluted Water. These results were helpful to understand the biogeochemical cycle of organic carbon and the trophic status of the East China Sea and the Yellow Sea. |
