YSI 6600传感器在太湖蓝藻预警工作中的应用

通过对太湖饮用水源地2个取水口水体中的蓝藻密度(CBD)和叶绿素(Chl)分别进行 YSI 6600-v2水质多参数仪和实验室显微镜检分析,探讨了CBD和Chl在预警工作中的应用.结果表明,在CBD与Chl相关性显著时期内,藻类群落结构相对稳定;CBD和Chl相关性不显著时期内,藻类群落结构变化较大.ρ(CBD)/ρ(...     

Selection of water source for water transfer based on algal growth potential to prevent algal blooms

Water transfer is becoming a popular method for solving the problems of water quality deterioration and water level drawdown in lakes. However, the principle of choosing water sources for water transfer projects has mainly been based on the effects on water quality, which neglects the influence in the variation of phytoplankton community and the risk of algal blooms. In this study, algal growth potential (AGP) test was applied to predict changes in the phytoplankton community caused by water transfer projects. The feasibility of proposed water transfer sources (Baqing River and Jinsha River) was assessed through the changes in both water quality and phytoplankton community in Chenghai Lake, Southwest China. The results showed that the concentration of total nitrogen (TN) and total phosphorus (TP) in Chenghai Lake could be decreased to 0.52 mg/L and 0.02 mg/L respectively with the simulated water transfer source of Jinsha River. The algal cell density could be reduced by 60%, and the phytoplankton community would become relatively stable with the Jinsha River water transfer project, and the dominant species of Anabaena cylindrica evolved into Anabaenopsis arnoldii due to the species competition. However, the risk of algal blooms would be increased after the Baqing River water transfer project even with the improved water quality. Algae gained faster proliferation with the same dominant species in water transfer source. Therefore, water transfer projects should be assessed from not only the variation of water quality but also the risk of algal blooms.     

Ecological Study of Spring-Early Summer Phytoplankton Blooms in A Semi-Enclosed Estuary

A sampling station in the Eastern Harbour of Alexandria was operated for 51 days between 2 March and 12 June, 1991. the harbour had different wide physical and chemical variations. Six distinct phytoplankton blooms occurred during this period. It is concluded that the physicochemical conditions affected the phytoplankton community structure and species composition. A dense diatom bloom could be maintained in a very weak and/or stabilized water column. A diatom bloom does not necessarily accompany an enhanced nutrient period. the depletion of nutrients and establishment of thermal stratification probably created favourable conditions for dinoflagellate and flagellate species to achieve blooms. the species composition could be shifted over the short term and a dense phytoplankton bloom could possibly dissipate in a few days.     

黄河三角洲河口区浮游植物组成及多样性分析

通过对2010年5月、8月、11月黄河三角洲主要河口浮游植物的调查,该水域共有浮游植物42种,以硅藻门所占比例较大;细胞密度为5.3×107～2.41×109ind/m3;生物多样性H为0.56～1.4,植物物种丰度指数D为0.06～0.36,均匀度指数J值均在0.5以上。结果表明:与莱州湾、渤海湾海域相比,黄河三角洲主要河口区浮游植物具有一定的淡水特征,种类组成及数量差异较大。黄河三角洲主要河流入水口处浮游植物的Shannon-Weaver多样性指数、Pielou均匀度指数与莱州湾、渤海湾海域相比差别不大,均较低。渤海水域主要河流入水口处营养状态均为中营养型以下,且春季好于夏秋两季,表现出一定的季节趋势。     

A multi-scale approach to modelling spatial and dynamic ecological patterns for reservoir's water quality management

With growing levels of urbanization and agriculture throughout the world, it is increasingly important that both research and management efforts take into account the effects of this widespread landscape alteration and its consequences for natural systems. Freshwater ecosystems, namely reservoirs, are particularly sensitive to land use changes. In this context, modelling can be very useful, for decision support, as an investigative tool to forecast the outcome of various scenarios, to guide current management in order to meet future targets and to develop integrated frameworks for management accordingly to the Water Framework Directive (WFD). The present paper examined the applicability of a holistic Stochastic-Dynamic Methodology (StDM), coupled with a Cellular Automata (CA) model, in capturing how expected changes at land use level will alter the ecological status of lentic ecosystems, namely at physicochemical and biological levels. The methodology was applied to Portuguese reservoirs located in the Douro's basin and illustrated with a series of stochastic-dynamic and spatial outputs taking into account expected scenarios regarding land use changes. Overall, the simulation results are encouraging since they seem to demonstrate the tool reliability in capturing the stochastic environmental dynamics of the selected metrics facing spatial explicit scenarios. The ultimate goal was to couple monitoring assessment and the described modelling techniques to ease management and decision making regarding the practical implementation of the WFD, both at the scale of the reservoir body and at the scale of the respective river watershed dynamics.     

Distribution of phytoplankton community and its influence factors in an urban river network,East China

To reveal the distribution characteristics of phytoplankton and the main influence factors under different conditions in the urban rivers, the investigations were conducted during autumn and winter 2014 in Changzhou City, East China. 178 taxa of phytoplankton belonging to 28 functional assemblages were identified. In autumn, the phytoplankton community compositions have high similarity for enhanced hydrological connectivity. The chlorophytes and diatoms (prevailing functional groups C, F, J, P), together with euglenoids (W1), showed high proportions of biomass in the main rivers and connected rivers. It was related to the well mixed eutrophic conditions. The phytoplankton community exhibited spatiotemporal heterogeneity in winter. Affected by the low water level and temperature, the free-living phytoflagellates (X2) replaced groups F and J in the main rivers. Phytoplankton productivity was the highest in the Tongji River. Chlorophytes Dictyosphaerium ehrenbergianum and Chlamydobotrys stellata had an overwhelming superiority during the winter bloom. They were significantly correlated with ammonium, total phosphorus and biochemical oxygen demand. Affected by tail water supply, the diatoms (MP) and euglenoids (W1) dominated in a beheaded river. The multivariate analyses based on the phytoplankton functional groups helped to evaluate the relationships and variations between the urban rivers. The redundancy analysis (RDA) results showed that nitrate nitrogen, water temperature, total nitrogen and total suspended solids were the main influence factors on the phytoplankton community. Except MP, the prevailing groups all showed significant negative correlations with nitrate nitrogen. Availability and utilization of dissolved inorganic nitrogen and hydrodynamic conditions affected the phytoplankton distribution.

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Origins and scales of hypoxia on the Louisiana shelf: Importance of seasonal plankton dynamics and river nutrients and discharge

Management plans for the Mississippi River Basin call for reductions in nutrient concentrations up to 40% or more to reduce hypoxia in the Gulf of Mexico (GOM), while at the same time the government is considering new farm subsidies to promote development of biofuels from corn. Thus there are possibilities of both increasing and decreasing river nutrients depending on national priorities. River flow rates which also influence the extent of hypoxia on the shelf may be altered by global climate change. We have therefore developed a series of simulations to forecast ecosystem response to alterations in nutrient loading and river flow. We simulate ecosystem response and hypoxia events using a linked model consisting of multiple phytoplankton groups competing for nitrogen, phosphorus and light, zooplankton grazing that is influenced by prey edibility and stoichiometry, sub-pycnocline water-column metabolism that is influenced by sinking fecal pellets and algal cells, and multi-element sediment diagenesis. This model formulation depicts four areas of increasing salinity moving westward away from the Mississippi River point of discharge, where the surface mixed layer, four bottom layers and underlying sediments are represented in each area. The model supports the contention that a 40% decrease in river nutrient will substantially reduce the duration and areal extent of hypoxia on the shelf. But it also suggests that in low and middle salinity areas the hypoxia response is saturated with respect to nutrients, and that in high salinity regions small increases in nutrient and river flow will have disproportionally large effects on GOM hypoxia. The model simulations also suggest that river discharge is a stronger factor influencing hypoxia than river nutrients in the Mississippi River plume. Finally, the model simulations suggest that primary production in the low salinity regions is light limited while primary production in the higher salinity zones is phosphate limited during the May to October period when hypoxia is prevalent in the Mississippi River plume.     

A three-component model of phytoplankton size class for the Atlantic Ocean

A three-component model was developed which calculates the fractional contributions of three phytoplankton size classes (micro-, nano- and picoplankton) to the overall chlorophyll-a concentration in the Atlantic Ocean. The model is an extension of the Sathyendranath et al. (2001) approach, based on the assumption that small cells dominate at low chlorophyll-a concentrations and large cells at high chlorophyll-a concentrations. Diagnostic pigments were used to infer cell size using an established technique adapted to account for small picoeukaroytes in ultra-oligotrophic environments. Atlantic Meridional Transect (AMT) pigment data taken between 1997 and 2004 were split into two datasets; 1935 measurements were used to parameterise the model, and a further 241 surface measurements, spatially and temporally matched to chlorophyll-a derived from SeaWiFS satellite data, were set aside to validate the model. Comparison with an independent global pigment dataset (256 measurements) also supports the broader-scale application of the model. The effect of optical depth on the model parameters was also investigated and explicitly incorporated into the model. It is envisaged that future applications would include validating multi-plankton biogeochemical models and improving primary-production estimates by accounting for community composition.     

Assesment of the response of a shallow macrotidal estuary to changes in hydrological and wastewater inputs through numerical modelling

The aim of this study was to investigate the response to short-term changes in river freshwater discharges and in nutrients loadings (mainly from the treatment of urban wastewater), of the shallow macrotidal Urdaibai estuary (north of Spain), by using numerical tools. A two-dimensional hydrodynamic model and a water quality model were applied to the estuary, in order to better use it as a prediction tool in the study of the effects of variations in hydrodynamic conditions and in waste water inputs. The model was calibrated and verified using data measured under different hydrological conditions (spring and summer). A model calibration was carried out with field data measured during the summer, while the model validation was conducted for spring conditions. The calibration process allowed the model parameter definition, while the model validation permitted the verification of the calibrated parameters under different environmental conditions. The model results were in reasonable agreement with field measurements, in both the calibration and the validation phases. The model showed a significant decrease in phytoplankton concentration with river input increase. A study on the effects of nutrient input reduction from the Gernika Waste Water Treatment Plant (WWTP) was conducted. It showed a decrease in phytoplankton concentration with decreasing levels of nutrient discharge. This reduction was more pronounced in conjunction with the highest river discharge. In that case, a 50% decrease for the elimination of the WWTP discharge was observed.     

The algal toxicity of silver engineered nanoparticles and detoxification by exopolymeric substances

In this study, we report that silver ions (Ag⁺) from the oxidative dissolution of silver engineered nanoparticles (Ag-ENs) determined the EN toxicity to the marine diatom Thalassiosira weissflogii. Most of the Ag-ENs formed non-toxic aggregates (>0.22 μm) in seawater. When the free Ag⁺ concentration ([Ag⁺]_F) was greatly reduced by diafiltration or thiol complexation, no toxicity was observed, even though the Ag-ENs were better dispersed in the presence of thiols with up to 1.08 × 10⁻⁵ M Ag-ENs found in the <0.22 μm fraction, which are orders of magnitude higher than predicted for the natural aquatic environment. The secretion of polysaccharide-rich algal exopolymeric substances (EPS) significantly increased at increasing [Ag⁺]_F. Both dissolved and particulate polysaccharide concentrations were higher for nutrient-limited cells, coinciding with their higher Ag⁺ tolerance, suggesting that EPS may be involved in Ag⁺ detoxification.