The Contribution of Ciliated Protozoa to Zooplankton Biomass in an Acidic, Subtropical Lake

Ciliated protozoa accounted for up to 50% of the mean daily zooplankton biomass in McCloud Lake, a small (5 ha), oligotrophic, acidic (pH 4.7) lake in north-central Florida. Food resources (algae and bacterioplankton) were limiting for crustacean and rotifer zooplankton during much of the year. Myxotrophic ciliates were a dominant component of the planktonic food web. Stentor niger , an uncommon species in the plankton of lakes, dominated the ciliate assemblage and usually comprised >90% of total ciliate biomass. Stentor niger always contained high densities of photosynthetic zoochlorellae and contributed an estimated 30% to the total autotrophic biomass.     

Contribution of the water-sediment interface to the transformation of biogenic substances: application to nitrogen compounds

Up to now the water-sediment interface (WSI) has not been considered by limnologists and oceanographers as a theoretical frontier between two phases, but as a variable layer comprising the overlying bottom water, the superficial sediment, and the bioturbed sediment. This heterogeneous benthic boundary layer forms a non-equilibrated assemblage of an aqueous phase, a mineral phase influencing the exchanges, and a dissolved gaseous phase regulating biological activity, detrital organic matter present as dissolved or adsorbed compounds and particles, and a living benthic community dominated by microorganisms. Biological activity and the equilibrium between these components are linked to depth, bottom currents, primary production and allochtonous inputs of organic matter. The settling rate of particulate matter in the water column, which depends on both the size and density of particles, is also an important factor. Settled organic matter is broken down mainly by heterotrophic microorganisms. In the first stage, dissolved or particulate matter is depolymerized by exoenzymes linked to the bacterial membrane. Other heterotrophic organisms, like flagellates and ciliates, contribute to the activity of bacterial populations or to a modification of the physical and chemical characteristics of organic matter like macrofauna. Bacterial activity in the WSI is one to two orders of magnitude higher than in overlying bottom water, depending on the density of the bacterial population, on the amount of available organic matter, and on the presence of predators grazing on bacteria and macrofauna and increasing oxygen and dissolved substrates. The WSI is now considered as a sink for particulate matter and biopolymers, and/or as a sink or source for organic monomers and NH₄ ⁺ depending on their concentrations. As a result of its contribution to mineral and organic cycles, the WSI is a crossroad for exchanges between aqueous and sediment layer. During the last decade, intensive work has been performed in this field, but progress has been slow due to the heterogeneity of the layer and the adsorptive properties of the mineral fraction.     

The Contribution of Gastropod Biomass in Macrobenthic Communities of a Karstic River

This study evaluated the standing crop biomass of freshwater snails and its spatial distribution according to four substrate types (boulders, cobbles, gravel covered with periphyton and gravel covered with macrophytes). The study site, in the Kupa River of the NW Dinarid area of Croatia, is in a karstic region. Depending on habitat, the gastropod wet biomass varied from 6.4% to 43.8% of the total macroinvertebrate biomass per unit area. The gastropods are the dominant component of biomass on boulder substrates in the upper region of the river, and on gravel substrates covered with macrophytes, in the lower course. It was found that gastropods are also the dominant component of the functional group of scrapers. The average annual gastropod biomass constitutes more than 80% of scrapers at sampling sites in the upper and lower regions of the river.     

The Effects of Hydrology on Plankton Biomass in Shallow Lakes of the Pampa Plain

Climatic and hydrological variability is usually high in the Pampa Plain (Argentina). However it has not studied yet how this variability may affect the phytoplankton and zooplankton biomass and community structure in aquatic systems of this region. The main purpose of this study was to assess flushing effects on nutrient and plankton dynamics in two interconnected very shallow lakes of the Pampa Plain. In order to study the impact of hydrology on the plankton biomass and community structure, we compared the summer plankton community among three consecutive years with contrasting hydrological characteristics. Water residence time varied an order of magnitude among years and this variability was correlated to strong changes in physicochemical and biological lake characteristics. Depending on the water discharge level, the hydrological regime within the lakes ranged from lentic to more lotic conditions. Nutrient and phytoplankton biomass were positively related to water discharges. During high flushing periods, nutrients import from intensive agriculture lands leads to a dramatic increase in trophic conditions. On the other hand, macrozooplankton biomass was positively related to water residence time and showed a dramatic decrease during high flushing years. Rotifers biomass was not affected by interannual water discharge variability during the study period. Our results support that in case of lakes with high flushing rates, zooplankton development is dependent on water residence time and that hydrology may have stronger effects on macrozooplankton biomass than top-down control by planktivores.     

PCR‐DGGE Fingerprinting Analysis of Plankton Communities and Its Relationship to Lake Trophic Status

Plankton communities in eight lakes of different trophic status near Yangtze, China were charac‐terized by using denatured gradient gel electrophoresis (DGGE). Various water quality parameters were also measured at each collection site. Following extraction of DNA from plankton communi‐ties, 16S rRNA and 18S rRNA genes were amplified with specific primers for prokaryotes and eu‐karyotes, respectively; DNA profiles were developed by DGGE. The plankton community of each lake had its own distinct DNA profile. The total number of bands identified at 34 sampling stations ranged from 37 to 111. Both prokaryotes and eukaryotes displayed complex fingerprints composed of a large number of bands: 16 to 59 bands were obtained with the prokaryotic primer set; 21 to 52 bands for the eukaryotic primer set. The DGGE‐patterns were analyzed in relation to water quality parameters by canonical correspondence analysis (CCA). Temperature, pH, alkalinity, and the con‐centration of COD, TP and TN were strongly correlated with the DGGE patterns. The parameters that demonstrated a strong correlation to the DGGE fingerprints of the plankton community differed among lakes, suggesting that differences in the DGGE fingerprints were due mainly to lake trophic status. Results of the present study suggest that PCR‐DGGE fingerprinting is an effective and precise method of identifying changes to plankton community composition, and therefore could be a useful ecological tool for monitoring the response of aquatic ecosystems to environmental perturbations. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Contribution of Urban Water Supply to Greenhouse Gas Emissions in China

Greenhouse gas (GHG) emissions from energy use in the water sector in China have not received the same attention as emissions from other sectors, but interest in this area is growing. This study uses 2011 data to investigate GHG emissions from electricity use for urban water supply in China. The objective is to measure the climate cobenefit of water conservation, compare China with other areas on a number of emissions indicators, and assist in development of policy that promotes low‐emission water supply. Per capita and per unit GHG emissions for water supplied to urban areas in China in 2011 were 24.5 kilograms carbon dioxide equivalent (kg CO₂‐eq) per capita per year and 0.213 kg CO₂‐eq per cubic meter, respectively. Comparison of provinces within China revealed that GHG emissions for urban water supply as a percentage of total province‐wide emissions from electricity use correlate directly with the rate of leakage and water loss within the water distribution system. This highlights controlling leakage as a possible means of reducing the contribution of urban water supply to GHG emissions. An inverse correlation was established between GHG emissions per unit water and average per capita daily water use, which implies that water demand tends to be higher when per unit emissions are lower. China's high emission factor for electricity generation inflates emissions for urban water supply. Shifting from emissions‐intensive electricity sources is crucial to reducing emissions in the water supply sector.     

The temporal and spatial patterns of protozooplankton abundance in a eutrophic temperate lake

The temporal and spatial distribution of planktonic protozoa of Esthwaite, a eutrophic lake, was investigated at 7–10 day intervals between February to October 1988. Sarcodine protozoa were of little significance, the plankton was dominated by ciliates and flagellates. Ciliate density peaked in late May to early June with densities reaching 9.2 × 10³ 1^-1. There was considerable variation in spatial distribution and greatest species diversity occurred in March/April. After the establishment of summer stratification the planktonic ciliates were confined to water of >25% oxygen saturation in the water column. Oligotrichs, particularly the genus Strombidium and tintinnids, and peritrichs dominated the ciliate assemblages. There was no correlation between chlorophyll a concentrations and ciliate numbers, but a correlation was apparent between ciliate numbers and flagellate density. There were significant differences between the protozooplankton communities at the different sampling sites in the lake.     

The Structure of a Macroinvertebrate Community in a Northern German Lake Outlet (Lake Belau,Schleswig-Holstein) with Special Emphasis on Abundance,Biomass and Secondary Production

The structure of macroinvertebrate communities was studied at I I sampling sites of the outlet of Lake Belau in the lowlands of northern Germany. To describe the structures of macrobenthic animal communities three different units were examined: abundance, biomass, and secondary production. 112 taxa were collected from the entire stream. The numbers of species ranged from 31 (fine sand) to 70 (submerged macrophytes). For the stream, average macroinvertebrate density was 18.400 ind. M⁻¹. Density was highest at the macrophytes amounting to 35,630 individuals per m², and lowest in the pure sand with only 3,900 ind. M⁻². Average biomass (dry mass) was 194 g DM m⁻² varying from 9.8 (peat) to 381 g DM m⁻² (gravel with mollusk shells near the upstream lake). For the stream, average annual production was 129 g DM m⁻² varying from 15 (peat) to 286 g DM m⁻² (macrophytes). The highest values for each unit were found in stream sections with gravel and submerged macrophytes. Lower values occured in sections that contained peat and sand. Usually, a single structure of the macroinvertebrate community was dominated by less than ten taxa, which varied at each sampling site depending on the units observed.     

Using fuzzy‐coded traits to elucidate the non‐random role of anthropogenic stress in the functional homogenisation of invertebrate assemblages

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嘉陵江浮游生物群落结构研究

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Ultraviolet Insights: Attempting to Resolve Enigmatic Patterns in Pelagic Freshwaters – The Historical Context and a View to the Future

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Structure and diversity of fishes in a freshwater and coastal subtropical lagoon

This study examined the fish communities of Peri Lagoon in southern Brazil to aid in the development of an effective management plan because the area is under threat from human activities. Sampling of fish fauna, ichthyoplankton and limnological data were compared between sites, differing by habitat type and characteristics such as depth, substratum composition and vegetation type. Results were significantly related to site, with the highest diversity and abundance recorded at shallow vegetated sites. A total of 14 fish species were recorded throughout the lagoon, with the most abundant being Hyphessobrycon luetkenii. Of the 14 species, half were sampled at their larval stage, suggesting a healthy and protected system. Significantly more larvae and eggs were collected during colder months (autumn to winter) and at sites closer to stream flow, possibly owing to increased food sources and habitat protection. This study highlights the importance of Peri Lagoon as a nursery ground for a wide range of fish species, providing essential information for incorporation into the future protection of fish stocks throughout Brazil.     

景观水体周丛生纤毛虫群落结构及其与环境因子的关系

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Marine Benthos in Relation to Pore Water Chemistry and Sediment Geochemistry of Simulated Dredged Material

During the course of study on vertical migration and mortality of benthos in simulated dredged material, changes in pore water chemistry and sediment geochemistry were also examined. Dissolved oxygen, ammonia, and sulfide showed significant changes between overlying water and pore water over the two week experimental period. Chemical effects in dredging operations can be important on infaunal organisms.     

Recent sedimentation in a freshwater reservoir in SW-Finland: The diatomological and chemical evidence of sediments on the development of the water body

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Morphological Description and Molecular Phylogeny of Two Species of Levicoleps (Ciliophora,Prostomatida), L. taehwae nov. spec. and L. biwae jejuensis nov. subspec., collected in Korea

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The morphology, ontogeny, and small subunit rRNA gene sequence analysis of Diophrys parappendiculata n. sp. (Protozoa, Ciliophora, Euplotida), a new marine ciliate from coastal waters of southern China

The morphology, morphogenesis, and phylogeny of Diophrys parappendiculata n. sp., a large marine ciliate isolated from the coastal waters of Daya Bay, southern China, were investigated. This new species is characterized by a combination of its large size, appendiculata-pattern of ciliature, and bipartite adoral zone of membranelles. The main stages of morphogenesis during binary fission were also recorded and described. Comparisons of morphological characteristics with similar congeners support the validity of the new species. The small subunit rRNA gene sequence of D. parappendiculata is 96.3-99.94% similar to those of four other congeners; it differs in four nucleotides from that of Diophrys appendiculata (i.e. structural similarity was 99.94%). Phylogenetic analysis indicates that D. parappendiculata n. sp. falls into the Diophrys clade and is most closely related to the well-known D. appendiculata.     

Number and Distribution of Superficial Neuromasts in Twelve Common European Cypriniform Fishes and Their Relationship to Habitat Occurrence

This paper gives the first detailed data on the number and body part related distribution of superficial neuromasts in twelve common European Cypriniform species and examines whether such anatomical variables can be related to rough scale habitat occurrence. The fishes (Barbatula barbatula, Barbus barbus, Chondrostoma nasus, Cobitis taenia, Leuciscus cephalus, Leuciscus leuciscus, Phoxinus phoxinus, Rutilus rutilus, Rhodeus sericeus, Scardinius erythrophthalmus, Tinca tinca, Vimba vimba) were classified in two generalized ‘ecological guilds’, 1) rheophilic and 2) limnophilic or indifferent, based on literature data. The total number of superficial neuromasts was consistent within each species, but differed considerably between species. Lowest numbers of superficial neuromasts were found in Barbatula barbatula (21 ± 4.9 superficial neuromasts per cm body length) (mean ± SD), highest numbers in Vimba vimba (233 ± 36.1). Both species can be classified as rheophilic. Over all no relationship was found between the total number of superficial neuromasts and large scale habitat occurrence. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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The Reference Index Method for the Macrophyte‐BasedAssessment of Rivers – a Contribution to the Implementationof the European Water Framework Directive in Germany

The European Water Framework Directive requires ecological status classification and monitoring of surface and ground waters using biological indicators. To act as a component of the “Macrophytes and Phytobenthos” biological quality element, as demanded by the Directive, a macrophyte‐based assessment system was developed for application in river site types in Germany. Macrophyte abundance data were collected from 262 sites in 202 rivers. Seven biocoenotic river site types were established using differences in characteristic macrophyte communities reflecting ecoregion, channel width, water depth, current velocity, water hardness, and ground water influence. For four of these river site types, a macrophyte assessment system was developed, for the remaining three river site types data were insufficient for developing an assessment system. Ecological status classification of river sites is based on the calculation of a Reference Index value, in some cases supplemented by additional vegetation criteria. The Reference Index quantifies the deviation of species composition and abundance from reference conditions and classifies sites as one of the five possible ecological quality classes specified in the Directive. The assessment of long river stretches with changing river site types along its course is discussed based on an example from the Forstinninger Sempt River, southeast Germany. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)