Bacterioplankton and phytoplankton production in seven lakes in the Middle Rio Doce basin, south-east Brazil

The purpose of this study was to measure the phytoplankton production (PP) and bacterial production (BP) simultaneously in seven lakes in the middle Rio Doce basin (southeast Brazil) during the dry and the rainy seasons. Limnological monitoring was conducted from 1999 to 2001 as well as both PP (radioactive carbon fixation) and BP (³H-Leucine incorporation) in four specific depths (100%, 10%, 1% of incident radiation, and aphotic zone). Furthermore, trophic state of the lakes was analyzed, considering the index proposed by Salas and Martino (1991) and Carlson (1977). In general, some parameters increased during the rainy season such as pH, conductivity, chlorophyll and total nitrogen. In the period of 1999/2000, the rain caused PP reduction in the lakes, excepting Carioca and Águas Claras Lake, but in the years 2000/2001, the lakes did not show a similar pattern. In contrast, the rainy season of both years caused an expressive bacterioplankton production enhancing. Using Salas and Martino index, we observed that some lakes were affected by the seasonal runoff, therefore the typologie of these lakes changed from oligotrophic to mesotrophic conditions, otherwise considering the Carlson index all lakes were classified as eutrophic in both dry and rainy seasons. Indeed, Salas and Martino index demonstrated to be more appropriate to determine the trophic status of the lakes. Finally, our data indicate that until now, in spite of the lakes location, protected and unprotected area, the lakes still maintain their natural characteristics.     

Planktonic algae and epiphyton of the littoral in lake Peipsi, Estonia

The littoral plankton of Lake Peipsi (3555 km², mean depth 7.1 m) was studied in summer 1980 and 2000–2002, and the epiphyton was studied on two dominating macrophytes, Phragmites australis (Cav.) Trin. ex Steud. and Potamogeton perfoliatus L., in 2000. The purpose of the study was to estimate to what extent the littoral phytoplankton and epiphytic algae (their biomass, chlorophyll a content and dominant species) can be used as a criterion for the trophic state of the lake. In wind-open areas, phytoplankton biomass in the littoral is commonly more than ten times higher than in open water due to the presence of the macroscopic cyanobacterium Gloeotrichia echinulata (J.S. Smith) P. Richter. This alga is abundant in the moderately eutrophic northern lake's part and rare in the strongly eutrophic southern part; hence also biomass in the southern part is considerably lower. In open water, phytoplankton biomass increases southward with increasing trophy. Algal biomass in the littoral depends on wind direction and can change completely in a few days. Epiphyton biomass and Chla content increased southward with increasing trophic state. They both revealed significant Spearman correlations (P < 0.05) with wind index and transparency (negative), and with abundance of the host plant, both reed and pondweed (positive). The phytoplankton biomass of the littoral of the large and shallow Lake Peipsi can not be used as a criterion of trophic state, however, the species composition of the dominants, particularly cyanobacteria, is well applicable for this purpose. The biomass and Chla content of the epiphyton can be used as a criterion for trophic state.     

Effects of freshwater inputs on the lower trophic levels of a temperate estuary: physical, physiological or trophic forcing?

The aim of this 6?year study was to assess whether freshwater inputs (rainfall and dam discharges) were acting as physical, physiological or trophic forcing factors on phytoplankton pigment concentrations and the dominant mysids of a temperate estuary (Guadalquivir estuary; SW, Spain). The effects of natural and human-controlled freshwater inputs modified the physico-chemical conditions and consequently biological production (bottom up control). Nutrient (nitrogen hypernutrification), suspended particulate matter and allochthonous photosynthetic pigment imports linked to freshwater inputs from adjacent habitats were observed, as well as light-limited autochthonous primary production. Seasonal and/or spatial patterns were shown by all study variables, including mysids. Freshwater management effects on dominant mysids differed depending on the species?? salinity tolerance (physiological forcing) and preferred prey availability (trophic forcing). Moreover, high inorganic matter content had a negative effect on the density of Mesopodopsis slabberi (physical forcing), which led to an increased detritivory/herbivory ratio (Neomysis integer/M. slabberi ratio). In conclusion, freshwater inputs appeared to effect estuarine lower trophic levels via a combination of different forcing mechanisms. Although several general patterns can be derived, the response of the system to freshwater inputs was not always univocal.     

Variation characteristics of heavy metals and nutrients in the core sediments of Taihu Lake and their pollution history

The sedimentary environment change, trophic evolution and heavy metals pollution history of the northern Taihu Lake in the last 100 years are studied according to the sedimentary geo-chemical proxies of the core sediments, such as grain size, nutrients, heavy metals, diatom, etc. The nutrients in the sediments depended mainly on the lake internal circulation and the heavy metals were from natural geogenic sources before the 1920s, which were not influenced by human activities generally, and grain size was one of the key factors influencing heavy metals content in the sediments. The alternation of manner and strength of human activities in Taihu Lake catchment before and after the 1920s made the lake sediments coarser, and hence heavy metals and TP content decreased contrasted with that before the 1920s. TP content in sediments and water increased from the 1950s to late 1970s due to anthropogenic pollutants discharge, and the lake belonging to mesotrophic state. TN and TOC content and C/N ratio increased due to the increasing external pollutants into Taihu Lake by human activities, TP content also increased obviously in water and sediments, and the diatom association was dominated by eutrophic species since the late 1970s, indicating the eutrophication state of Taihu Lake in this period. Meanwhile the increasing in heavy metals content, such as Cu, Mn, Ni, Pb and Zn, and their proportion of valid fractions in the sediments indicates that they all result from human pollutants since the late 1970s. The heavy metals in the surface sediments have certain potential biological toxicity due to the higher SEM/AVS ratio.     

Variation characteristics of heavy metals and nutrients in the core sediments of Taihu Lake and their pollution history

The sedimentary environment change, trophic evolution and heavy metals pollution history of the northern Taihu Lake in the last 100 years are studied according to the sedimentary geochemical proxies of the core sediments, such as grain size, nutrients, heavy metals, diatom, etc. The nutrients in the sediments depended mainly on the lake internal circulation and the heavy metals were from natural geogenic sources before the 1920s, which were not influenced by human activities generally, and grain size was one of the key factors influencing heavy metals content in the sediments. The alternation of manner and strength of human activities in Taihu Lake catchment before and after the 1920s made the lake sediments coarser, and hence heavy metals and TP content decreased contrasted with that before the 1920s. TP content in sediments and water increased from the 1950s to late 1970s due to anthropogenic pollutants discharge, and the lake belonging to mesotrophic state. TN and TOC content and C/N ratio increased due to the increasing external pollutants into Taihu Lake by human activities, TP content also increased obviously in water and sediments, and the diatom association was dominated by eutrophic species since the late 1970s, indicating the eutrophication state of Taihu Lake in this period. Meanwhile the increasing in heavy metals content, such as Cu, Mn, Ni, Pb and Zn, and their proportion of valid fractions in the sediments indicates that they all result from human pollutants since the late 1970s. The heavy metals in the surface sediments have certain potential biological toxicity due to the higher SEM/AVS ratio.     

Coupling effects of hydrological characteristics and nutrient load in sediments on the trophic state of reservoirs

Currently,lakes and artificial reservoirs are increasingly threatened by eutrophication,which is the result of the combined action of many natural and anthropogenic factors.In the past,the effect of nutrient load on the trophic state of water bodies has attracted much attention,while few studies have addressed the effect of hydrological characteristics.Therefore,to reveal the coupling effects of hydrological characteristics and nutrient load in sediments on the trophic state of water bodies,this study collected relevant data from 36 lakes and reservoirs across China.Pearson correlation analysis showed that trophic level index was positively and significantly correlated with nutrient load in sediments and hydraulic retention time,while it was negatively correlated with mean depth and hydraulic load.The principal component analysis showed that the nutrient load was the first major component that influenced the trophic state of water bodies,followed by the mean depth and hydraulic retention time.Eutrophication was prone to occur in water bodies with mean depth less than 7 m and hydraulic retention time greater than 14 d,and the trophic level index regression equation with hydrological characteristics and nutrient load in sediments was derived by multiple regression analysis.This study revealed that the trophic state of water bodies influenced by both nutrient load and hydrological characteristics.It provides a new idea to reduce the occurrence of eutrophication in reservoirs by using the artificial hydrological regulation capacity of reservoirs.     

Tracing the influence of sewage discharge on coastal bays of Southern Vancouver Island (BC,Canada) using sedimentary records of phytoplankton

The impact of sewage and stormwater effluents on phytoplankton is investigated by comparing organic-walled dinoflagellate cyst abundance and diversity from 38 surface sediment samples, flanking southern Vancouver Island. Site locations include those directly adjacent to wastewater outfall at Clover and Macaulay Points and Saanich Peninsula, as well as from a variety of near-shore environments with differing tidal flow influences. Excellently preserved dinoflagellate cyst assemblages have been recovered and 36 cyst taxa were identified. Local assemblages are characterized by a high relative proportion (average 56%) of cysts produced by heterotrophic dinoflagellates, which is typical for regions of high primary production. Relative proportional increases of cysts from heterotrophic species with particular increases of Polykrikos kofoidii/schwartzii and Dubridinium species, known to reflect areas affected by eutrophication, occur directly adjacent to all three sewage outfalls, as well as in the more stagnant waters of Esquimalt and Victoria Harbours and at the mouth of Cadboro Bay. Further effects of an anthropogenic effluent can be seen in the relatively higher concentrations of organic carbon and the diatom production proxy, biogenic opal. Results from this study clearly indicate a much larger impact zone than predicted by a sewage effluent plume model or trends found in monitored benthic biota and sediment chemistry that evidence primary outfall affects <800 m eastward of Macaulay Point and about 200 m eastward of the Clover Point. Enhanced production of cysts from potentially toxic Alexandrium species is also observed near locations of sewage outfalls.     

Assessment of the ecological status of transitional waters in Sicily (Italy): First characterisation and classification according to a multiparametric approach

A 1-year cycle of observations was performed in four Sicilian transitional water systems (Oliveri-Tindari, Cape Peloro, Vendicari and Marsala) to characterise their ecological status. A panel of variables among which trophic and microbial (enzyme activities, abundance of hetetrophic bacteria and of bacterial pollution indicators) parameters, were selected. Particulate organic carbon (POC) and nitrogen (PON) and chlorophyll-a (Chl-a) contents defined the trophic state, while microbial hydrolysis rates and abundance gave insights on microbial community efficiency in organic matter transformation and on allochthonous inputs. To classify the trophic state of examined waters, the synthetic trophic state index (TRIX) was calculated.Microbial hydrolysis rates correlated positively with POC and Chl-a, which increased along the eutrophication gradient. The significant relationships among TRIX, trophic and microbial parameters suggested the use of leucine aminopeptidase, alkaline phosphatase and POC as suitable parameters to implement the Water Framework Directive when assessing the ecological status of transitional water systems.     

Reconstruction of historical nutrient levels in Korean and Japanese coastal areas based on dinoflagellate cyst assemblages

Dinoflagellate cysts acquired from sediment cores were analyzed in order to reconstruct historical nutrient levels in Gamak Bay, Korea and Ariake Bay, Japan. Dinoflagellate cyst assemblages in Gamak Bay were characterized by high proportions of heterotrophic cysts such as Brigantedinium spp., Protoperidinium americanum and Polykrikos cysts, which suggested that nutrients levels may have already been high before 1970s, and then increased further to the hypertrophic conditions of the 1990s. In contrast, dinoflagellate cyst assemblages in Ariake Bay were characterized by high relative abundances of Lingulodinium machaerophorum and Spiniferites spp., which suggested that nutrient levels in Ariake Bay had increased gradually since the mid 1960s, and may have been significantly enhanced by the mid 1980s. Dinoflagellate cyst assemblages reflecting environmental changes in the two bays are contrasting, perhaps due to different nutrient enrichment mechanisms. This suggests that the indicators of nutrient levels encoded in dinoflagellate cyst assemblages may exhibit site-specific information.     

Ecotoxicological monitoring in lakes of Northwestern and Central European Russia situated in specially protected natural areas

An ecotoxicological assessment is given to the state of small lakes in specially protected natural areas in Northwestern and Central European Russia, which suffer from aerotechnogenic acidification. The toxicity of water and bottom sediments is shown to increase with decreasing water pH. The most sensitive characteristics of aquatic organisms in different trophic groups are chosen, allowing the state of lakes to be monitored.     

Tropical harmful algal blooms: An emerging threat to coral reef communities?

Tropical harmful algal blooms (HABs) are increasing in frequency and intensity and are substantially affecting marine communities. In October/November 2008 a large-scale HAB event (> 500 km², dinoflagellate Cochlodinium polykrikoides) in the Gulf of Oman caused the complete loss of the branching corals, Pocillopora and Acropora spp., and substantial reductions in the abundance, richness and trophic diversity of the associated coral reef fish communities. Although the causative agents of this C. polykrikoides bloom are unknown, increased coastal enrichment, natural oceanographic mechanisms, and the recent expansion of this species within ballast water discharge are expected to be the main agents. With rapid changes in oceanic climate, enhanced coastal eutrophication and increased global distribution of HAB species within ballast water, large-scale HAB events are predicted to increase dramatically in both intensity and distribution and can be expected to have increasingly negative effects on coral reef communities globally.     

A late-glacial and post-glacial history of amsoldingersee and vicinity,Switzerland

A multidisciplinary approach was used to study the Late-Glacial and Post-Glacial history of a Swiss Plateau lake. Pollen analysis revealed thirteen major changes in vegetation. A series of coordinated fluctuations in vegetation and lacustrine trophic status were found, which were partially interpreted as the result of climatic changes. Oxygen isotope ratios revealed three major shifts in temperature which correspond with alterations in vegetation composition, sediment composition and lake trophic status. Cladoceran microfossils and fossil pigments were used as indicators of trophic status and reflected periods during which the lake was partially anoxic.     

黄淮海平原封丘试区水体营养状态的综合评价

选择封丘试区内有代表性的7类水体,对其营养状态进行综合评价和聚类分析,初步提出了用于水体营养状态评价的方法和标准。结果表明:各水体营养状态可依其植物组成而明显分成挺水植物、沉水植物和浮游植物型等,而且草型水体的营养指数均高于藻型水体。总的看来,该试区各类水体营养状态较为相似,营养指数均很高,属富营养—重富营养型,渔业发展潜力较大。     

Temporal and spatial characteristics of dissolved organic carbon in the Wujiang River,Southwest China

River systems play an important role in the global carbon cycle. Rivers transport carbon to the ocean and also affect the carbon cycle in the coastal ocean. The flux from land to the ocean is thought to be a very important part of the land carbon budget. To investigate the effect of dam-building on dissolved organic carbon(DOC)in rivers, three reservoirs of different trophic states in the Wujiang basin, Guizhou Province, were sampled twice per month between May 2011 and May 2012. Temporal and spatial distributions of DOC in the reservoirs and their released waters were studied. It was found that different factors controlled DOC in river water, reservoir water, and released water. DOC in the rivers tended to be affected by primary production. For reservoirs, the main controlling factors of DOC concentration varied by trophic state. For the mesotrophic Hongjiadu Reservoir, the effect of primary production on DOC concentration was obvious. For the eutrophic Dongfengdu Reservoir and the hypereutrophic Wujiangdu Reservoir, primary production was not significant and DOC came instead from soil and plant litter.     

Assessing the environmental conditions of rivers on the northern coast of Lake Ladoga by chemical characteristics and the structure of hydrobiocenoses

The chemical features and the structure of biological communities in Lake Ladoga are considered. Comparative analysis was carried out for the species composition and biomass of phytoperiphyton, zooplankton, and zoobentbos in six Ladoga tributaries based on observational data of August 2013. The effect of natural and anthropogenic factors on the formation of the structure of river hydrobiocenoses is analyzed. The trophic status of rivers, their saprobiological state, and the significance of individual communities and biotic indices for bioindication of the ecological state of rivers are estimated.     

Eutrophication of Surface Water in the Arctic Region

The problem of eutrophication of the surface water in the Arctic Regions is discussed. The natural hydrochemical indices of the trophic status of lakes are analyzed in connection with the landscape and physiographic features of the Kola Peninsula. The regular features of changes in the hydrochemical indices of the trophic status of lakes and the development of the process of eutrophication are analyzed in the case of subarctic Lake Imandra, which has been polluted with municipal and industrial (phosphorus-containing waste of the apatite production) wastewater for more than fifty years. Criteria are proposed for establishing and assessing water eutrophication in cold climate.     

Integrated application of 3D seismic and microseismic data in the development of tight gas reservoirs

The development of unconventional resources, such as shale gas and tight sand gas, requires the integration of multi-disciplinary knowledge to resolve many engineering problems in order to achieve economic production levels. The reservoir heterogeneity revealed by different data sets, such as 3D seismic and microseismic data, can more fully reflect the reservoir properties and is helpful to optimize the drilling and completion programs. First, we predict the local stress direction and open or close status of the natural fractures in tight sand reservoirs based on seismic curvature, an attribute that reveals reservoir heterogeneity and geomechanical properties. Meanwhile, the reservoir fracture network is predicted using an ant-tracking cube and the potential fracture barriers which can affect hydraulic fracture propagation are predicted by integrating the seismic curvature attribute and ant-tracking cube. Second, we use this information, derived from 3D seismic data, to assist in designing the fracture program and adjusting stimulation parameters. Finally, we interpret the reason why sand plugs will occur during the stimulation process by the integration of 3D seismic interpretation and microseismic imaging results, which further explain the hydraulic fracture propagation controlling factors and open or closed state of natural fractures in tight sand reservoirs.     

Long-term variations of the trophic state index in the Narochanskie Lakes and its relation with the major hydroecological parameters

Variations of the trophic status of lakes Batorino, Myastro, and Naroch were analyzed over a long period of 1978–2013. The lakes form a system of interconnected water bodies with a wide range of trophic states. In the period under consideration, the trophic conditions in the lakes varied from highly eutrophic (Lake Batorino) to oligotrophic (Lake Naroch), making it possible to analyze the long-term changes in the trophic state of the lakes with the use of different variants of evaluating the Carlson index (trophic state index, TSI), to assess the relationship between the three versions of the index with one another, with phytoplankton biomass, and with hydroecological characteristics, such as the concentrations of total N, seston, and organic matter and biochemical oxygen demand. The possibility to evaluate the index by other characteristics, including phytoplankton biomass, was also considered.