Study Of Fluorescent Dissolved Organic Matter And Its Relationship With Environmental Factors In East China Sea And Yellow Sea Waters

Dissolved organic matter plays an integral role in shaping aquatic system as it directly and indirectly influences the physical, chemical and biological processes of the ocean. And fluorescence is one of the most important optical properties of DOM in seawater. The fluorescence characteristics of DOM in East China Sea and Yellow Sea and their relationship with terrestrial inputs, phytoplankton multiplication and other environmental factors are researched in this thesis. The main results are as follows:(1) The excitation-emission matrix spectra of East China Sea waters during 2005 spring phytoplankton bloom contains both high and low excitation-wavelength tyrosine-like peaks (B and D), tryptophan-like peaks (T and S) and UV humic-like peak (A).(2) While the excitation-emission matrix spectra of East China Sea waters during 2006 spring only contains high excitation-wavelength tyrosine-like peak (B),low excitation-wavelength tryptophan-like peak (S) and UV humic-like peak.(3) In surface waters, the distribution patterns of FDOM in East China Sea for both years are the same: Fluorescence intensities are higher in the coastal areas and decrease toward outer sea, indicating strong terrestrial influences; While the distributions and sources of FDOM in transects are complex, have both influences of terrestrial and in situ production from phytoplankton and sediment releases. And the distribution of FDOM reflects that of DOM to some extents.(4)The relationships between fluorescence intensities and Chla concentrations are poor even during the phytoplankton bloom, which implies that the level of in situ production of FDOM by phytoplankton is very small with respect to the strong terrestrial influences. The reasonable negative correlations between FDOM and salinities suggest terrestrial inputs as the main sources, while the random in situ production and sinks destroy the conservative mixing curve of fluorescence and salinity. The relationship between humic-like fluorescence and nutrients indicates that they have rather different geochemical processes in coastal sea areas.(5)The excitation-emission matrix spectra of Yellow Sea waters during 2006 spring contains both high and low excitation-wavelength tyrosine-like peaks (B and D), tryptophan-like peaks (T and S) and UV humic-like peak. The distribution patterns of FDOM in Yellow Sea are controlled by its water masses distribution.(6)Despite the differences of nutrients concentrations and algae growths, the changes of the peak positions and the intensities are the same in series of mesocosm experiments: High and low excitation tyrosine-like peaks (B and D), low excitation tryptophan-like peak (S) and UV humic-like peak exist from the beginning of the cultivations; their intensities continue to increase and at the same time the peak positions of high excitation tyrosine-like peak (B) red shift as the experiments progress; high excitation tryptophan-like (T) and visible humic-like (C) peaks appear on the 6th day and all the peak intensities reach their highest level where they all correspond to a much higher Chla concentrations; afterwards, tyrosine-like peaks (B and D) disappear and all the other peak intensities decrease; the high and low excitation protein-like peak may vary independently. Dissolved oxygen and pH have no apparent influences on peak positions and intensities of FDOM. Fluorescence can indicate DOM ideally.