Distributions And Influencing Factors Of Carbohydrates In The Coastal Seawaters Of China

The latitude span of Yellow Sea, Bohai Sea and East China Sea is large. Sotheir ecological environment, ocean circulation conditions are different.Carbohydrate is the main identified component in the seawater, which is the majormaterial including energy, storage and structure. At the same time, carbohydrateplays an important role in the marine food chain cycle and marine carbon cycle. Theresearch on biogeochemical behavior of dissolved and colloidal carbohydrate in theChina shelf sea, is very meaningful to understand the migration of organic matter. Inthis paper several samples of dissolved carbohydrates were selected in the coastalwaters, including the Yellow Sea, the Bohai Sea, the East China Sea and the YangtzeRiver estuary. The concentration distribution, influence factor, temporal and spatialvariation and the ratio between components of monosaccharides (MCHO),polysaccharides (PCHO), and total dissolved carbohydrate (TCHO), PCHO andTCHO were investigated. Meanwhile, each component’s contribution to the totaldissolved organic carbon (DOC) and the allocation and distribution of colloidalcarbohydrates in each phase were also investigated. The main conclusions of thispaper are as follows:(1) The distribution of dissolved carbohydrates presents high nearshoreand lowopen sea as a whole. The horizontal distribution law which is high at estuary low inopen sea and the distribution trend declines gradually from inshore to offshore. Atthe same time they also show the seasonal variationthat is high in summer and lowin autumn. The reason why there are regional differences of MCHO、PCHO andTCHO in various sea areas is thatphytoplankton biomass is different because ofvarious productivity in various sea areas.(2) Concentrations of DOC, chlorophyll a (Chl-a), MCHO, PCHO and TCHO in the Yellow Sea and the Bohai Sea were measured in the autumn of2010. Thevariation of the ratios of MCHO and PCHO and the distributions of MCHO, PCHOand TCHO inthe surface layer and microlayer were also measured. The resultsindicated that the concentration of MCHO, PCHO and TCHO in the sea-surfacewater of the Bohai Sea and the Yellow Sea ranged from1.1,2.6and8.9to15.2,39.1and41.9μmol C/L, with averages of7.4,15.4and23.8μmol C/L. The high valueareas were found near the Bohai bay, Laizhoubay and Shandong peninsula likeWeihai and Yantai. The average of the ratio of TCHO/DOC were13.8%and16.1%in the Yellow Sea and the Bohai Sea, it explained that DOC had been an importantpart of carbohydrate. The horizontal distributions of MCHO, PCHO and TCHOdisplayed a decreasing trend from inshore to offshore sites.A significant positiverelationship was found between PCHO/TCHO ratios; Carbohydrates exhibitedenrichment in the microlayer, and average EF value of MCHO, PCHO, TCHO andDOC was2.63,1.81,2.0and1.5, respectively. The extent of enrichment ofcarbohydrates in the microlayer was related with many factors such as wind speed,diffusion, scavenging bubbles and adsorption.(3) The concentration of MCHO、PCHO and TCHO in different depth of theEast China Sea was measured in the summer and autumn of2012. The results of thispaper indicated that the concentration of MCHO, PCHO and TCHO ranged from3.3,2.7and7.9to14.8,15.4and25.7μmol C/L in the East China Sea in summer. Theaverage of MCHO, PCHO and TCHO was8.0,9.7�'�17.7μmol C/L. The high valueareas were found near the coastal areas, and decreased gradually along with theextension of the water. The concentration of MCHO, PCHO and TCHO ranged from0.3,1.9and2.3to5.2,11.9and12.1μmol C/L in the East China Sea in autumn. Theaverage of MCHO, PCHO and TCHO was2.7,4.8and7.5μmol C/L. Thecontributions of MCHO, PCHO and TCHO to DOC was2.9%,4.9%and7.8%, Theresult indicated that PCHO had been an important part of DOC in surface seawaters.The East China Sea dissolved carbohydrate’s concentration was significantly higher than the survey results of autumn. This is because it was affected by the YangtzeRiver diluted water and the Kuroshio current, and the distribution of carbohydratesin the surfacewater of East China Sea also gradually decreasing from inshore tooffshore. Terrigenous input is the main reason why PCHO is high near the YangtzeRiver estuary. It further demonstrates that PCHO is the main component of TCHO.(4) This study gave a detailed analysis and discussion on DCHO and impactfactor of DH3and DH4fracture surface. The contribution of TCHO by Yangtzediluted water to the Yellow Sea and The East China Sea was about30%, this numberindicated that the Yangtze diluted water made a great contribution to transportingTCHO to the Yellow Sea and the East China Sea. Due to the limitation of primaryproduction of phytoplankton affected the release of carbohydrates, the DH3sectionappears low DCHO concentration area in the east. The distribution of DH8-9showsthe vertical distance distributionof MCHO and PCHO affected by the kuroshio water.The concentrations of PCHO showed a diurnal variation at an anchor station withthe highest value at12:00to16:00and lowest value at night. The concentration ofMCHO was later than that of PCHO. This observation further supported thehypothesis that MCHO was derived, in part, from the hydrolysis of PCHO.(5) Cross-flow ultra-filtration was used inseparating sea waters in severalstations which are near the Yellow Sea and Yangtze River estuaries. Mass balanceexperiment was used to calculate the recovery rate of DOC and carbohydrates. Theresult showed that most were within the scope of the recovery which was identifiedby literatures. Three kinds of carbohydrate components were found in the truesolution, this means that carbohydrate which dissolved in the solution is animportant part of the carbohydrates. Although MCHO, PCHO and TCHO accountedfor the proportion of “dissolved”carbohydrates are inorder,29.1%、17.6%and23.5%, colloid DCHO is also an important repository of dissolved form. The DOCand carbohydrate concentration in colloid changes affected by the mutual influence of terrigenous input and the life activities of phytoplankton.