Spatial analysis for spring bloom and nutrient limitation in Xiangxi bay of three Gorges Reservoir

The spatial and temporal dynamics of physical variables, inorganic nutrients and phytoplankton chlorophyll a were investigated in Xiangxi Bay from 23 Feb. to 28 Apr. every six days, including one daily sampling site and one bidaily sampling site. The concentrations of nutrient variables showed ranges of 0.02–3.20 mg/L for dissolved silicate (Si); 0.06–2.40 mg/L for DIN (NH₄N + NO₂N + NO₃N); 0.03–0.56 mg/L for PO₄P and 0.22–193.37 μg/L for chlorophyll a, respectively. The concentration of chlorophyll a and inorganic nutrients were interpolated using GIS techniques. The results indicated that the spring bloom was occurred twice in space during the whole monitoring period (The first one: 26 Feb.–23 Mar.; the second one: 23 Mar.–28 Apr.). The concentration of DIN was always high in the mouth of Xiangxi Bay, and PO₄P was high in the upstream of Xiangxi Bay during the whole bloom period. Si seems no obvious difference in space in the beginning of the spring bloom, but showed high heterogeneity in space and time with the development of spring bloom. By comparing the interpolated maps of chlorophyll a and inorganic variables, obvious consumptions of Si and DIN were found when the bloom status was serious. However, no obvious depletion of PO₄P was found. Spatial regression analysis could explained most variation of Chl-a except at the begin of the first and second bloom. The result indicated that Si was the factor limiting Chl-a in space before achieved the max area of hypertrophic in the first and second bloom period. When Si was obviously exhausted, DIN became the factor limiting the Chl-a in space. Daily and bidaily monitoring of Site A and B, representing for high DIN: PO₄P ratio and low DIN:PO₄P ratio, indicated that the concentration of Si was decreased with times at both site A and B, and the dramatically drop of DIN was found in the end monitoring at site B. Multiple stepwise regression analysis indicated that Si was the most important factor affect the development of spring bloom both at site A and B in time series.     

Water quality assessment using integrated modeling and monitoring in Narva Bay, Gulf of Finland

A coupled three-dimensional hydrodynamic–ecological model was used for the assessment of water quality in Narva Bay during one biologically active season. Narva Bay is located in the south-eastern Gulf of Finland. Narva River with a catchment’s area covering part of Russia and Estonia discharges water and nutrients to Narva Bay. The ecological model includes phytoplankton carbon, nitrogen and phosphorus, chlorophyll a, zooplankton, detritus carbon, nitrogen and phosphorus, inorganic nitrogen, inorganic phosphorus and dissolved oxygen as state variables. Both the hydrodynamic and ecosystem models were validated using a limited number of measurements. The hydrodynamic model validation included comparison of time series of currents and temperature and salinity profiles. The ecological model results were compared with the monitoring data of phytoplankton biomass, total nitrogen and phosphorus and dissolved oxygen. The comparison of hydrodynamic parameters, phytoplankton biomass, surface layer total phosphorus and dissolved oxygen and near-bottom layer total nitrogen was reasonable. Time series of spatially mean values and standard deviations of selected parameters were calculated for the whole Narva Bay. Combining model results and monitoring data, the characteristic concentrations of phytoplankton biomass, total nitrogen and phosphorus and near-bottom dissolved oxygen were estimated. Phytoplankton biomass and total phosphorus showed seasonal variations, of 0.6–1.1 and 0.022–0.032 mg/l, respectively, during spring bloom, 0.1–0.3 and 0.015–0.025 mg/l in summer and 0.2–0.6 and 0.017–0.035 mg/l during autumn bloom. Total nitrogen and near-bottom oxygen concentrations were rather steady, being 0.25–0.35 and 2–6 mg/l, respectively. The total nitrogen and phosphorus concentrations show that according to the classification of Estonian coastal waters, Narva Bay water belongs to a good water quality class.     

Assessing the micro-phytoplankton response to nitrate in Comau Fjord (42°S) in Patagonia (Chile), using a microcosms approach

Anthropogenic (aquaculture) changes in environment nutrient concentrations may affect phytoplankton (biomass and taxa composition) in marine coastal waters off the Chilean Patagonia. The effects of adding nitrate (NO₃ ^?) to natural phytoplankton assemblages were evaluated considering biomass, cell abundance, and taxonomic composition. Microcosm experiments were performed in the spring, summer, and winter in the Comau Fjord located in Subantarctic Patagonia. At the end of the experiments, NO₃ ^? decreased rapidly and was undetectable in treatments, indicating a strong NO₃ ^? deficiency associated with an exponential increase in Chl-a concentrations, particulate organic nitrogen, and carbon in these treatments. Moreover, given the depleted nitrate concentrations of the spring and summer experiments, the micro-phytoplankton taxa structure shifted from mixed diatom and dinoflagellate assemblages (Ceratium spp., Dinophysis spp., Coscinodiscus sp., Rhizosolenia pungens) to assemblages dominated by blooms of the classic chain-forming diatoms found in temperate and cold waters such as Chaetoceros spp., Skeletonema spp., and Thalassiosira spp. Thus, nitrogen sources (i.e., nitrate, ammonia) may influence phytoplankton abundance and biomass accumulation dynamics in the northern section of Patagonia. It also emphasizes the importance of diatom taxa in regards to the short-term response of phytoplankton to changing environmental nutrient conditions due to natural (decreasing freshwater stream flow) and anthropogenic (aquaculture) events. This situation may be one of the future scenarios in the Patagonian fjords, thus stressing the needs for active environmental monitoring and impact assessment.     

Temporal and spatial variability of phytoplankton monitored by a combination of monitoring buoys,pigment analysis and fast screening microscopy in the Fehmarn Belt Estuary

For 2 years, a baseline investigation was carried out to collect reference information of the present environmental status in the Fehmarn Belt and adjacent area. The temporal and spatial variability of phytoplankton was monitored by a combination of monitoring buoys, pigment analysis and fast screening microscopy. The overall phytoplankton succession in the Fehmarn Belt area was found to be influenced primarily by the seasonal changes, where various diatoms dominated the spring and autumn blooms and flagellates like Chrysochromulina sp., Dictyocha speculum and various dinoflagellates were occasionally abundant in late spring and summer. The phytoplankton groups were remarkably uniform horizontally in the investigation area while large differences in both biomasses and composition of individual phytoplankton groups were seen vertically in the water column, especially in the summer periods, in which the two-layer exchange flow between the North Sea and the Baltic Sea is showing a particularly strong stratification in the Fehmarn Belt. The chlorophyll a concentrations ranged continuously from 1 to 3 μg/L at the three permanent buoy stations during the 2 years of monitoring, except for the spring and autumn blooms where chlorophyll a increased up to 18 μg/L in the spring of 2010 and up to 8 μg/L in the autumn of 2009. Recurrent blooms of filamentous cyanobacteria are common during the summer period in the Baltic Sea and adjacent areas, but excessive blooms of cyanobacteria did not occur in 2009 and 2010 in the Fehmarn Belt area. The combination of the HPLC pigment analysis method and monitoring buoys continuously measuring fluorescence at selected stations with fast screening of samples in the microscope proved advantageous for obtaining information on both the phytoplankton succession and dynamic and, at the same time, getting information on duration and intensity of the blooms as well as specific information on the dominant species present both temporally and spatially in the large Fehmarn Belt area.     

Controlling factors of phytoplankton seasonal succession in oligotrophic Mali Ston Bay (south-eastern Adriatic)

Fine spatial and temporal phytoplankton variability in Mali Ston Bay has been observed for the first time based on physicochemical properties and small herbivorous zooplankton. Extensive year-through research was conducted during 2002 at Usko station which is traditionally an area of intensive shellfish farming. The Neretva River inflow, submarine springs (“vruljas”) and precipitation are additional sources of nutrients in the bay. Temperature and salinity, combined with total inorganic nitrogen (TIN) were observed to be the most important environmental factors driving the succession of phytoplankton communities. Orthophosphate was a potential limiting factor for phytoplankton development. The nanophytoplankton abundances, as well as the microphytoplankton diatoms are controlled by herbivorous zooplankton grazing (‘top-down’ control) more than other groups of microphytoplankton. Nanophytoplankton dominated phytoplankton abundance and its most intensive development was recorded in winter and spring, while increase in microphytoplankton abundance occurred in spring and autumn. Diatoms dominated microphytoplankton abundance mostly in winter and autumn, while dinoflagellates dominated in spring and summer. Considering the number of taxa and abundance, dinoflagellates were the dominant microphytoplankton group during the year and were the main component of the spring blooms. At that time, in conditions of elevated temperature (>16 °C), decreased salinity (34–36) and increased concentrations of TIN, blooms of harmful dinoflagellate Prorocentrum minimum were recorded for the first time in the bay. The results showed a significant difference in environmental conditions, as well as in the annual phytoplankton succession and community structure, as compared with studies carried out more than 20 years ago in this area.     

An assessment of water quality and primary productivity in Perdido Bay,a Northern Gulf of Mexico Estuary

Perdido Bay is a shallow estuarine system of approximately 130 km² with three major freshwater inputs. On a seasonal basis the productivity and chlorophyll a concentration of phytoplankton in Perdido Bay are controlled by temperature. One input, Eleven Mile Creek, is influenced by a paper mill discharge. Eleven Mile Creek exhibits high levels of light attenuation, high concentrations of dissolved nutrients, and low rates of carbon fixation that are significantly different from the other inputs or areas of Perdido Bay and productivity in Eleven Mile Creek is light limited. Upper Perdido Bay had slightly elevated concentrations of dissolved nutrients which correlate with significantly higher rates of carbon fixation and phytoplankton biomass. Nutrients and color from Eleven Mile Creck are diluted by the Perdido River inflow, restricting nutrient and light limitations to the area at the mouth of Eleven Mile Creek.     

Inter-relations between biological and physicochemical factors in a database for a shallow estuarine system

This paper examines data obtained since 1976 in Peel Inlet and the Harvey Estuary, a shallow estuarine system in Western Australia, which has nuisance growths of macroalgae and seasonal blooms of the cyanobacterium (blue-green alga)Nodularia spumigena. Data collected at the same sites at weekly or fortnightly intervals include phytoplankton (chlorophylla), water nutrients (nitrogen and phosphorus), salinity, temperature and light penetration. Seasonally, the biomass of macroalgae has been measured at a number of sites and used to estimate total biomass.The data are characterised by large season-to-season differences, attributable to the seasonality and volume of river flow. The information has been used to relate the magnitude of summer blue-green algal blooms to the winter loading of phosphorus from the surrounding catchment, and the magnitude of macroalgal biomass to light penetration through the water column.     

Investigating the impacts of treated effluent discharge on coastal water health (Visakhapatnam,SW coast of Bay of Bengal,India)

The present study investigated the impacts of treated effluent discharge on physicochemical and biological properties of coastal waters from three pharmaceuticals situated along the coast of Visakhapatnam (SW Bay of Bengal). Seawater samples were collected (during the months of December 2013, March 2014 and April 2014) from different sampling locations (Chippada (CHP), Tikkavanipalem (TKP) and Nakkapalli (NKP)) at 0- and 30-m depths within 2-km radius (0.5 km = inner, 1 km = middle and 2 km?=?outer sampling circles) from the marine outfall points. Physicochemical and biological parameters, which differed significantly within the stations, were likely to be influenced by strong seasonality rather than local discharge. Dissolved oxygen variability was tightly coupled with both physical and biological processes. Phytoplankton cell density and total chlorophyll (TChla) concentrations were significantly correlated with dissolved inorganic nutrient concentrations. CHP (December) represented a diatom bloom condition where the highest concentrations of diatom cells, total chlorophyll (TChla), dissolved oxygen coupled with lower zooplankton abundance and low nutrient levels were noticed. The centric diatom, Chaetoceros sp. (>?50%) dominated the phytoplankton community. TKP (March) represented a post-diatom bloom phase with the dominance of Pseudo-nitzschia seriata; zooplankton abundance and nutrient concentrations were minimum. Conversely, NKP (April) represented a warm well-stratified heterotrophic period with maximum zooplankton and minimum phytoplankton density. Dinoflagellate abundance increased at this station. Relatively higher water temperature, salinity, inorganic nutrients coupled with very low concentrations of dissolved oxygen, TChla and pH were observed at this station. Copepods dominated the zooplankton communities in all stations and showed their highest abundance in the innermost sampling circles. Treated effluent discharge did not seem to have any significant impact at these discharge points.     

贵州黔东南州三板溪水库春季拟多甲藻水华特征

2011年3月13日对贵州省黔东南州三板溪水库进行春季浮游植物调查的结果表明,三板溪水库Ⅱ号采样点(下革东)发生以佩纳形拟多甲藻为优势种的拟多甲藻水华,细胞密度高达1.15×10⁷cell/L;板溪水库总氮的最低值为2.09 mg/L,总磷的最低值为0.95 mg/L,三板溪水库的总氮、总磷含量较丰富,不存在总氮或总磷是限制性因子;通过SPSS16.0统计软件分别进行Pearson 积距相关系数分析表明,氮磷比是三板溪水库发生拟多甲藻水华的主要影响原因。     

香溪河库湾氮的时空分布及影响因子分析

为研究解决香溪河库湾水体富营养化问题，需探明库湾水体氮的时空分布及影响因子。2010年12月—2011年11月对香溪河与水库干流交界处至香溪河库湾尾部共12个采样点进行连续监测，分析香溪河库湾氮的时空分布，结果表明，香溪河库湾氮存在明显的时空分布规律。空间上，回水末端处TN和NO₃^--N浓度低，河口处浓度高，随着与回水末端距离的增加，浓度逐渐升高。在时间上，香溪河库湾TN和NO₃^--N浓度的变异系数随着与河口距离的增加总体上逐渐增大，研究时间内的变化程度逐渐变大；且香溪河库湾TN和NO₃^--N浓度在三峡水库不同运行阶段的时间变化规律不同。