Xiaoyong Shi

Environmental capacity of nitrogen and phosphorus pollutions in Jiaozhou Bay, China: modeling and assessing.

In recent years, with the development of society and economy of Qingdao, environment and ecosystem problems, for instance, red ties, become more and more serious in Jiaozhou Bay, China, because of the increasing pollutants discharged into it. In order to solve these problems, an eco-hydrodynamic model is constructed to estimate the marine environmental capacity of nitrogen and phosphorus nutrients in Jiaozhou Bay, whose simulation results are rational for the bay. According to the model, if the target is set to achieve water quality (grade II) in Jiaozhou Bay, the environmental capacity of dissolved inorganic nitrogen and phosphorus in one year are approximately 7800 and 840 tons, respectively. Thus our research offers necessary scientific foundation to the total loads control efforts in this area.

Invasin of Edwardsiella tarda is essential for its haemolytic activity, biofilm formation and virulence towards fish

The aim of this study was to investigate the role of invasin in a bacterial fish pathogen Edwardsiella tarda.

Investigation of seasonal variability of CDOM fluorescence in the southern changjiang river estuary by EEM-PARAFAC

The southern Changjiang River Estuary has attracted considerable attention from marine scientists because it is a highly biologically active area and is biogeochemically significant. Moreover, land-ocean interactions strongly impact the estuary, and harmful algal blooms (HABs) frequently occur in the area. In October 2010 and May 2011, water samples of chromophoric dissolved organic matter (CDOM) were collected from the southern Changjiang River Estuary. Parallel factor analysis (PARAFAC) was used to assess the samples’ CDOM composition using excitation-emission matrix (EEM) spectroscopy. Four components were identified: three were humic-like (C1, C2 and C3) and one was protein-like (C4). Analysis based on spatial and seasonal distributions, as well as relationships with salinity, Chl a and apparent oxygen utilization (AOU), revealed that terrestrial inputs had the most significant effect on the three humic-like Components C1, C2 and C3 in autumn. In spring, microbial processes and phytoplankton blooms were also important factors that impacted the three components. The protein-like Component C4 had autochthonous and allochthonous origins and likely represented a biologically labile component. CDOM in the southern Changjiang River Estuary was mostly affected by terrestrial inputs. Microbial processes and phytoplankton blooms were also important sources of CDOM, especially in spring. The fluorescence intensities of the four components were significantly higher in spring than in autumn. On average, C1, C2, C3, C4 and the total fluorescence intensity (TFI) in the surface, middle and bottom layers increased by 123%–242%, 105%–195%, 167%–665%, 483%–567% and 184%–245% in spring than in autumn, respectively. This finding corresponded with a Chl a concentration that was 16–20 times higher in spring than in autumn and an AOU that was two to four times lower in spring than in autumn. The humification index (HIX) was lower in spring that in autumn, and the fluorescence index (FI) was higher in spring than in autumn. This result indicated that the CDOM was labile and the biological activity was intense in spring.

An ecosystem model of the phytoplankton competition in the East China Sea, as based on field experiments

An ecological dynamic model for the simulation of two pelagic phytoplankton groups is developed in this article. Model parameters were adjusted and validated based on the light-limited field culture experiments and the mesocosm experiments in the East China Sea (ECS). The calculation comparisons from the proposed model, along with field experiment observations, show that the model simulate the datasets very well, qualitatively and quantitatively. The parameters’ sensitivity analysis indicates that the competition between the diatoms and dinoflagellates is most sensitive to the photosynthetic process, followed by the exudation process of the phytoplankton, while the autolysis and respiration processes of phytoplankton and the grazing and exudation processes of zooplankton can also influence this competition to some extent. The sensitive parameters include: the photosynthetic optimal specific rate; the optimal irradiance and optimal temperature for phytoplankton growth; and the half-saturation constant for limiting nutrients, etc. Results of the sensitivity analysis also indicate that light, temperature and limiting nutrients are the controlling environmental factors for the competition between the diatoms and dinoflagellates in the ECS. In order to explore the effects of light and nutrients on the phytoplankton competition, simulations were carried out with varying light and nutrient conditions. Model simulations suggest that the diatoms favor higher irradiance, lower DIN/PO4–P ratios, higher SiO4–Si/DIN ratios and higher nutrient concentrations, as compared to the dinoflagellates. These results support the speculation that the increase in the DIN/PO4−P ratio and the decrease in the SiO4–Si/DIN ratio in the ECS may be responsible for the composition change in the functional Harmful Algal Bloom (HAB) groups from the diatom to the dinoflagellate communities over the last two decades.

Contribution of biological processes to self-purification of water with respect to petroleum hydrocarbon associated with no. 0 diesel in Changjiang Estuary and Jiaozhou Bay, China

Mesocosms in 25-m3 ethylene vinyl acetate or 4-m3 polyethylene bags were performed at two sites in China: Changjiang Estuary in spring–summer 1998, and Jiaozhou Bay in autumn 1999 and spring–summer 2000. The experiments were designed to show the contributions of physical, physicochemical and biological processes to self-purification of water with respect to the water-soluble fraction (WSF) of petroleum hydrocarbon associated with No.0 diesel (PHAD). Over the experimental periods, the WSF-PHAD concentration in water declined significantly. A kinetic model for WAS-PHAD distribution in multiphase environments – in this case water (W), suspended sediment (SS), phytoplankton (PPT), zooplankton (ZPT) and atmosphere (ATM) – was developed to estimate the contributions of the various processes. In the model, the key processes responsible for self-purification include (1) physical transport by volatilization from W to ATM; (2) biological transformation through biodegradation; (3) biological transfer involving bioconcentration by PPT and ZPT; and (4) physicochemical transfer through sorption by SS. Model parameters were determined from the mesocosm experiments and parallel laboratory experiments, or taken from the literature. It indicated that volatilization plays an important role in short-term self-purification especially regarding alkanes with relatively low molecular weight, accounting for 82.9±2.5%. After the volatilization stops, bioconcentration by PPT contributes greatly to long-term self-purification especially regarding alkanes of higher molecular weight and polycyclic aromatic hydrocarbons (PHAs), accounting for 0.7 – 17.8% with an average of 7.8±7.3%. The bioconcentration is dominated by biomass of PPT as well as the WSF-PHAD concentration. However, the biodegradation process makes the greatest contribution to both the short- and long-term self-purification, affecting alkanes of both lower and higher molecular weight as well as PHAs. The results suggest that it is necessary to take into account the biological processes of biodegradation and bioconcentration in estimating the self-purification of water with respect to oil pollutants.

The assessment of the spatial and seasonal variability of chromophoric dissolved organic matter in the Southern Yellow Sea and the East China Sea.

Samples of chromophoric dissolved organic matter (CDOM) from the Southern Yellow Sea (SYS) and the East China Sea (ECS) were evaluated by fluorescent Excitation Emission Matrix (EEM) combined with Parallel Factorial Analysis (PARAFAC). Three terrestrial humic-like components (C1, C2 and C3) and one autochthonous protein-like component (C4) were identified. As for seasonal variations, CDOM displayed the following order on the whole: summer>spring>autumn. The C1, C2 and C3 components were mainly dominated by terrestrial inputs and their spatial distributions and temporal variations also can be influenced by primary productivity of phytoplankton, microbial activities and photobleaching. C4 was produced by phytoplankton and microorganisms and consumed by marine bacteria, and besides its distribution was attributed to the influence of riverine inputs. Terrestrial inputs were the dominant sources of CDOM in the SYS and ECS.

Level and fate of heavy metals in the Changjiang estuary and its adjacent waters

Dissolved concentrations of Cu, Pb, Zn, and Cd were measured in the Changjiang estuary and its adjacent waters. The results indicate that the ranges of dissolved heavy metals in the studied waters are as follows: Cu = 1.0−6.9 μg/L, Pb = 0.10−0.39 μg/L, Zn = 3.2−9.1 μg/L, and Cd = 0.011−0.049 μg/L. The behavior of the dissolved Cu was essentially conservative, but a high scatter was observed for the high salinity samples, and it is the same with Zn and Pb. The overall concentrations of dissolved Cd increase with the salinity. There were no differences between the surface, middle, and bottom layer for Cu, Pb, Zn, and Cd. Seasonal changes of their averages were not obvious on the whole. River discharges, sedimentary dynamics, and biological processes might determine the profiles of heavy metals.

Characterization of Chromophoric Dissolved Organic Matter (CDOM) in the Bohai Sea and the Yellow Sea Using Excitation-Emission Matrix Spectroscopy (EEMs) and Parallel Factor Analysis (PARAFAC)

Compositions and concentrations of chromophoric dissolved organic matter (CDOM) have been determined in the Bohai Sea (BS) and the Yellow Sea (YS) in the summer and autumn in 2013 by excitation and emission matrix spectroscopy (EEMs) and parallel factor analysis (PARAFAC). The PARAFAC model identified three humic-like components (C1, C2, and C3) and one protein-like component (C4). CDOM exhibited higher fluorescence intensities in the coastal areas in both the summer and autumn. However, its distribution patterns were different in the two seasons. Based on spatial and seasonal distributions of four components, as well as correlations with salinity, chlorophyll a (Chl-a), and apparent oxygen utilization (AOU), the following assignments were made. The C1, C2, and C3 components were mainly dominated by terrestrial inputs and influenced by the primary productivity of phytoplankton in the summer as well. C4 was assigned to terrestrial and autochthonous origins and most likely represented a biologically labile component. Terrestrial inputs were the dominant source of CDOM in the BS and YS. The humification index (HIX) and biological index (BIX) suggested that CDOM in the BS was more stable than that in the YS, which had an increase in autochthonous production, and in the summer, CDOM was less stable with a higher CDOM autochthonous production compared with that in the autumn.

Modeling total maximum allocated loads for heavy metals in Jinzhou Bay, China.

With the recent development of society and economy in the cities of Huludao and Jinzhou, Liaoning Province, China, environment and ecosystem problems have become increasingly serious in Jinzhou Bay, China, because of the increasing amount of heavy metal pollutants being discharged. To solve these problems, a water quality model of heavy metals coupled with a 3D hydrodynamic model is constructed to estimate the environmental capacity (EC) and total maximum allocated loads (TMALs) for Zn and Cd of three river catchments in Jinzhou Bay. According to the model, the ECs for Zn and Cd are approximately 17 and 8 tons per month, respectively, if the criterion obtained from HC5 values (fifth percentile of the SSD) is set as the control criterion (8.24 μg/L for Zn and 3.83 μg/L for Cd) in Jinzhou Bay, and the TMALs of the three river catchments are 4 and 1.7 tons per month.

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.