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Characterization of chromophoric dissolved organic matter (CDOM) in the East China Sea in autumn using excitation-emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC)

Samples of chromophoric dissolved organic matter (CDOM) in the East China Sea in autumn (October in 2011) were analyzed by excitation emission matrix (EEM) fluorescence spectroscopy combined with parallel factor analysis (PARAFAC). Three terrestrial humic-like components (C1, C2 and C3) and one protein-like component (C4) were identified. Based on spatial distributions, as well as relationships with salinity, the following assignments were made. The three humic-like components (C1, C2 and C3) showed conservative mixing behavior and came mainly from riverine input. The protein-like component (C4) was considered a combination of autochthonous production and terrestrial inputs and a biologically labile component. Path analysis of samples from the middle and bottom layers revealed that the causal effects on C1 were −78.46% for salinity, and −21.54% for apparent oxygen utilization (AOU); those on C2 were −76.43% for salinity, and −23.57% for AOU; those on C3 were −70.49% for salinity, 7.01% for Chl-a, and −22.50% for AOU; those on C4 were −55.54% for salinity, 14.6% for Chl-a, and −29.86% for AOU in middle layer; and those on C4 were −57.37% for salinity, 29.02% for Chl-a, and −13.61% for AOU in bottom layer. Results indicated that CDOM in the East China Sea was mainly affected by terrestrial inputs, and microbial activities also played a key role in biogeochemical processes of CDOM. The application of the EEM-PARAFAC model presented a unique opportunity to observe compositional changes in CDOM in the East China Sea. In addition, the humification index (HIX) suggested that CDOM from the East China Sea was less stable and stayed shorter in the environment.

A study on biosorption and biodegradation of tributyltin by two red tide microalgae

The biosorption and biodegradation of tributyltin (TBT) at sublethal concentration of the two microalgae Leptocylindrus danicus and Amphidinium carterae were investigated. The results showed that accumulation of TBT occurred in the two algae, the adsorption of TBT by the algal cell wall was a rapid process. The degraded products, dibutyltin (DBT) and monobutyltin (MBT), were not detected in the incubation medium during the exposure periods of 9 days. Both algae have internal mechanism for degrading TBT to the less toxic fraction DBT, and also for DBT to MBT. It is worth noting that the Intracellular concentration of MBT was higher than that of DBT for Amphidinium carterae, which indicated that Amphidinium carterae could transformed DBT to MBT in a quick way relatively.

A fluorometric differentiation technique of phytoplankton assemblage based on Coif2 wavelet and fourth-derivative

The 3D discrete fluorescence spectra with 12 excitation wavelengths (400, 430, 450, 460, 470, 490, 500, 510, 525, 550, 570, 590nm) were determined by fluorescence spectrophotometer for 20 phytoplankton species. Then, the wavelet (Coif2), fourth-derivative and non-negative least squares were applied to establish the fluorescence differentiation method which could differentiate phytoplankton populations at the levels of both division and genus. This method was tested: for simulative mixed samples (the dominant division algae accounted for 50%, 70%, 90% and 100% of the gross biomass, respectively) at the level of division, the discrimination rates were 94.4%, 97.8%, 98.6%, and 98.4% with average relative content of 48.2%, 65.1%, 79.4% and 77.9%, respectively. For simulative mixed samples(the dominant species accounted for 70%, 80%, 90% and 100% of the gross biomass, respectively) at the level of genus, the correct discrimination rates were 72.7%, 82.2%, 86.5% and 81.0%, respectively. For the in situ test, all of the 12 samples were recognized at the division level, and for the three samples which the dominant species accounted for more than 80% of the gross biomass, the dominant species of one was recognized at the genus level. As a result, an in situ algae fluorescence auto-analyzer which uses a series of LEDs as the light sources is developing. The technique also can be directly applied on fluorescence spectrophotometer.

A fluorescence discrimination technique for the dominant algae species developed by Wavelet packet

In this study, a fluorescence spectra discrimination technique for red tide algae by Wavelet packet transform was developed. The fluorescence excitation-emission spectra were determined by fluorescence spectrophotometer for 24 red tide algae. Then the coefficient vectors (candidate feature spectra) were obtained by decomposition of Coiflets-2 wavelet packet. Bayesian discrimination was applied to select the feature spectra from the feature spectra and the norm spectra database was established by Cluster analysis. Finally, the discrimination technique was developed by multivariate linear regression and non-negative least squares. The results showed: for the simulative samples, when the dominant algae species accounted for 60%, 70%, 80%, 90% of the gross biomass, the CDR (correct discrimination ratio) of the dominant algae species at division level were 83.5%, 99.1%, 99.6% and 99.9% with the average relative content of 58.52%, 68.36%, 77.66%, 86.33%, respectively; and when the dominance of the dominant algae species accounted for 60%, 70%, 80%, 90%, 100%, the CDR of the dominant algae species at genus level were 86.13%, 94.91%, 95.25%, 96.78%,97%, respectively. For 12 samples collected from the mesocosm experiments in Maidao Bay, the CDR of the dominant algae species was 91.7% at division level, and that of the dominant algae species was 80% at genus level for the five samples that the dominance of dominant algae species reached to 80% according to the results of microscopic counting. For 12 samples collected from Jiaozhou Bay in August 2007, the CDR of of the dominant algae species was 100% at division level, and the dominant algae species of two samples were correctly recognized at genus level for three samples which dominant algae species accounted for 80% of the gross biomass according to the results of microscopic counting.

Distribution of chromophoric dissolved organic matter in Yellow Sea by Fluorescence Excitation-Emission matrix Regional Integration

Fluorescence Excitation Emission Matrix (FEEM) is often used to characterize the composition and properties of Chromophoric Dissolve Organic Mater (CDOM) in the freshwater and seawater. This research adopted Fluorescence Regional Integration (FRI) to assess the dynamics of CDOM in the Yellow Sea. FEEMs were delineated into five Excitation-Emission regions (five fluorophores): tyrosine-likematerial (Region I, λ<inf>Ex</inf>/λ<inf>Em</inf>=240–250nm/250–330nm), tryptophan-likematerial (Region II, λ<inf>Ex</inf>/λ<inf>Em</inf>240–250nm/330–380nm), fulvic acid-like materials (Region III, λ<inf>Ex</inf>/λ<inf>Em</inf>=240–250nm/380–580nm), microbial byproduct-like material (Region IV, λ<inf>Ex</inf>/λ<inf>Em</inf>=250–480nm/250–380nm) and humic acid-like material (RegionV, λ<inf>Ex</inf>/λ<inf>Em</inf>=250–480nm/380–580nm). The total fluorescence regional integration (Ф<inf>T,n</inf>) of FEEMs can be used as a good index for CDOM concentration, which is better than the traditional one-point fluorescence method. Fluorescence regional integration value of each fluorophore (Ф<inf>i,n</inf>) also was a good index to characterize CDOM composition and distribution. Fluorescence regional integration proportion of humic acid-like material (V) decreased gradually from coastal to coast, suggesting that fluvial input was the primary source of CDOM in the coastal, while fluorescence regional integration proportion of protein-like fluorophores (I and II) and microbial byproduct-like material (Region IV) increased, indicating an obvious contribution of biological activity within this area. For fulvic acid-like materials (III), there was a large high-value area, which indicated that both fluvial input and biological activity had contributions. All fluorescents, especially the protein-like fluorescence peaks (I and II) in the middle layer were higher than those from the surface layer and bottom layer, suggesting that the vertical distribution of CDOM in those stations were controlled by CDOM photochemistry or biological activity.

Assessing the composition of phytoplankton populations by fluorescence spectra

A fluorimetric method for differentiation of phytoplankton classes was developed based on GHM multiwavelet. The 3D fluorescence spectra date of 32 phytoplankton species dominant in coastal area of China sea were decomposed into different scale vectors and wavelet vectors by GHM multiwavelet. Then Ca2 vectors was selected as characteristic spectra by Bayesian discriminant analysis, and Ca2 reference spectra were obtained via systematic cluster analysis to the fluorescence characteristic spectra, then the phytoplankton composition fluorescence determination technology was developed by Multivariate Linear Regression resolved by Nonnegative Least Squares. The Ca2 reference spectra were utilized to identify the samples composed of one phytoplankton species: the average correctly identification rates were 97.6% at division and 86.9% at genus level respectively. For simulate mixed samples (the proportion of dominant division were 50%, 75% and 90%), the average correctly identification rates were 95.5%, 95.6% and 96.6%, the average relative content were 48.5%, 71.0% and 81.7% at division level. For the dominant species (the proportion were 60%, 70% and 90%), the average correctly identification rates were 78.0%, 85.5% and 90.0% at genus level. For in situ test, the results complied with microscopic examination at division level, the average relative content ranged from 76.2% to 96.0%, for the three samples with over 80% relative dominance of one phytoplankton species, two were identified correctly at genus level.