Study On Phytoplankton Of Changjiang Estuary Hypoxia Area And The Adjacent East China Sea

In recent years, the Yangtze river estuary hypoxia area showed a trend ofdeterioration,the Yangtze river is China’s first big river, with annual run-off up to9.32x1011m3, the basin area of180square kilometersSquare kilometers, closing to1/5of thenation’s total. The Yangtze estuary is one of the important rivers in China, around it isdeveloped economy, industrial prosperity, at the same time also has important fishinggrounds and culture zones, the waters of the changjiang diluted water, the coastalcurrent, Taiwan warm current and the kuroshio water mass, the influence of theecological environment is complicated.Dissolved oxygen in the sea water has close relation with the growth of Marineplankton, biological activity in the coastal waters, water sports, temperature, runoff andprecipitation can influence on the variation of dissolved oxygen in the water distribution.Since the1950s, scholars found that ocean exists low oxygen zone, Yangtze riverestuary waters in recent years, the Yangtze river estuary and adjacent waters findings inlow oxygen increasing, from the causes of low oxygen area, low oxygen zone to thehypoxia zone Marine biological conditions all have involved, many scholars studyshows that hypoxia area is a natural formation, is closely related to human activities.Yangtze river estuary in summer the hypoxia zone formation mechanism is verycomplex, is a process in the physical and biochemical processes interact. Found thatdissolved oxygen minimum area in the bottom of Yangtze river estuary in summer, as ithappens and changjiang diluted water carrying large amounts of suspended organicmatter deposition area corresponding to the largest, bottom layer suspended organicmaterial oxidation decomposition consumes a large amount of dissolved oxygen (do);Summer water layer is stable, water exchange is not fully up and down, hard to getdissolved oxygen supply, make the Yangtze river estuary waters underlying easyforming low-oxygen zone; Hypoxia area position changes with the seasons. Marine phytoplankton plays an important role in the marine ecosystem, as the maincontributor of marine primary productivity, in the material cycle and energy conversionplays a very important role in the process, the biomass and the amount of speciesdirectly affects the area of production and the balance of ecosystem, the carbon cycleand global climate change, the key role is increasingly attention.The study put the dissolved oxygen value is less than2mg/L sea area as the core oflow oxygen zone, the dissolved oxygen is greater than2mg/L less than3mg/L area asnon-core hypoxic zones, the dissolved oxygen is greater than3mg/L area as thehypoxia zone.This article through to in August2011, the Yangtze estuary hypoxia phytoplanktondistribution zone and adjacent sea area, temperature, salinity, dissolved oxygen, nitrate,phosphate, nitrite, suspended solids, the investigation of factors such as chlorophyll a,adopting internationally accepted Utermohl methods identify phytoplankton andanalysis of the Yangtze estuary hypoxia zone and adjacent sea phytoplankton speciescomposition, abundance, community diversity and its level distribution, low oxygenzone, the distribution characteristics of phytoplankton community, the relationshipbetween the phytoplankton and environmental factors in order to the Yangtze riveresrtuary low-oxygen zone and adjacent waters ecosystem of phytoplankton communityto provide basic data for further research. Main conclusions are as follows:1. In August2011Yangtze estuary hypoxia area mainly in30.75°N-31.5°N,122.5°E-123.25°E nearby waters, in the Yangtze estuary coast tank area, low oxygenzone mainly in the investigation of sea bottom, low dissolved oxygen was1.85mg/L,core low-oxygen zone range is30.6°.N-31.1°N,123°-123°03°E,core low oxygenzone covers an area of about1028km~2.2.82phytoplankton samples for Utermohl method analysis, the appraisal result is4door37genera and82species,21genera, bacillariophyta49species, accounted for56.8%of the types of identification; Pyrrhophyta14genera and30species, accountedfor38.5%of the identification; Coloring dinoflagellates1species of genus1door,cyanophyta1is2kinds. frame of dominant species is algae (Skeletonema costatum),ecological types in the temperate zone nearshore and euryhaline is given priority to, alsohave a small amount of warm water and ocean species, cell abundance between6.31x106cells/L~6.31x10~6cells/L, with a mean of7.59x10~5cells/L, the plane distributionfeatures from coast to coast, a trend of decrease, the vertical distribution characteristics is also reduces from the surface to the underlying trend, but below20m layer ofphytoplankton quantity is less.3. Found that core low oxygen, non-core low oxygen and low oxygen no differencebetween the phytoplankton species in the area, mainly diatom, but cells abundance,diversity index in sequence as the core hypoxia area> non-core hypoxia area> thehypoxia zone, the amount of dissolved oxygen to the cells of phytoplankton abundancedid not significantly influence.4. Surface phytoplankton abundance and temperature, nitrate, phosphate,chlorophylla, chemical oxygen demand (cod) were significantly positive correlation;And salinity, dissolved oxygen, suspended matter, nitrite and ammonia and pH valuewere significantly negative correlation. Underlying phytoplankton abundance werepositively correlated with temperature, and suspended solids, phosphate, nitratenegatively correlated, suggesting that the underlying phytoplankton growth nutrientlimitation.