Temporal and Spatial Distribution Characteristics of Colored Dissolved Organic Matter in Coastal Waters of Jiangsu Province

Colored Dissolved Organic Matter (CDOM) is one of important ocean color factors. In the background of “Jiangsu Coastal Development”, it is important to monitor the water quality and pollution status of coastal waters by analyzing its spatial and temporal distribution characteristics with remote sensing data. This paper was based on the high temporal resolution of Geostationary Ocean Color Imager (GOCI) image downloaded from Korea Ocean Satellite Center. The temporal-spatial distribution of CDOM in Jiangsu coastal waters was analyzed on daily, weekly and monthly time scales from April, 2011 to May, 2016. CDOM in Jiangsu coastal waters are mainly terrigenous, and higher inshore than that of offshore. The monthly average concentration of CDOM in the western coast of the South Yellow Sea was 0.167~0.201 m^-1, and those of central and southern regions were 0.086~0.187m^-1. The maximum values were outside the maximum turbidity zone of the Yangtze River Estuary, which was 0.180~0.206 m^-1 (absorption coefficient at 440 nm). The diurnal variation of CDOM in near shore waters was found to coincide with the change of tide, which decreased at first and then increased in the sea area. By fitting the monthly mean using cosine function, significantly cyclical variation of mean CDOM was found in the South Yellow Sea. The central region of the South Yellow Sea waters fitting coefficient was 0.823. Affected by the Yellow Sea cold water mass, the sub-regions of the South Yellow Sea changed seasonally, whose CDOM concentration in winter and spring was higher than that in summer and autumn. Because of Changjiang Diluted Water and other water masses, seasonal variation of the Yangtze River Estuary was contrary to that of the South Yellow Sea. On monthly scale, CDOM concentration was positively correlated with total suspended matter, with correlation coefficient r being 0.72. The trend of the central and southern region was more significant.     

Microbial production and photobleaching of CDOM in an estuarine brackish lake on Chongming Island, Shanghai

Chromophoric dissolved organic matter （CDOM）, one of the important components in freshwater and seawater ecosystems, plays a role in underwater light absorption and primary productivity. The Lake Beihu was a part of the North Branch of the Yangtze （Changjiang） River estuary in the past, but now the Lake Beihu has become the biggest manmade brackish lake in East China. The lake is a unique brackish ecosystem, however, little study deals with the fate of CDOM in it and whether this type of lake ecosystem will face eutrophication problem. This paper focuses on the transformation of CDOM, and the impact of microbe and light in the Lake Beihu. Microbial production and natural photobleaching simulative experiment was done on water samples from the Lake Beihu, yielding the following results. Water samples were collected from the Lake Beihu in May 2006. The filtrates through Whatman GF/F filters and polycarbonate membranes （μm） were exposed to microbe and microbe plus light condition, respectively. Three-dimensional excitation emission matrix （3-DEEM） fluorescence spectra were analyzed. It was shown that the amount of CDOM increased with time in the microbe exposure experiment, which means that microbes may play an important role in the production of CDOM instead of degrading CDOM. The .productivity was enhanced with increasing temperature, e.g. the value of UV260 increased by 62.4% in 4.5 days at 30℃, 26.9% at 20℃, 5.0% at 10℃. In addition, photobleaching was observed in the study as other papers reported. With the impact of microbes, the fluorescence signal of fulvic acid became stronger as the time went by. At 30℃, the fulvic acid fluorescence, which was expressed by QSU, increased by 35%-39%.     

长时序Landsat的北极Lena河DOC浓度变化及驱动力分析

北极Lena河是世界第十长河,也是北极地区第二大河,其年径流量约占北冰洋淡水总量的20％,同时将陆地生态系统上的大量有机物携带进海洋,并且在全球碳循环中起到非常重要的作用.卫星遥感数据是监测河流有机碳循环的重要数据源,特别是在无冰期的高纬度地区.本研究的目的是:(1)建立一种高精度反演算法估算北极Lena河的溶解有机碳...