Long-term (30 years) dynamics of Chironomidae (Diptera) fauna in the Kuibyshev water reservoir associated with eutrophication processes

Benthos investigations were carried out in the channel and flood-plain of the Kuibyshev water reservoir during 1958–1985. Hydrobiological monitoring data obtained at 12–16 stations in all Deeps excluding littoral areas are discussed. In 1987–1900 benthofauna distribution was also studied at the Priplotinny Deep. An increase of the reservoir trophic state is reported. The observed trend was an increase of the total benthos biomass. Changes in both species and trophic structure of the chironomid community due to the eutrophication problem are discussed.     

Phytoplankton composition and pigment concentrations as indicators of water quality in the Rybinsk reservoir

Long-term changes in phytoplankton (1954–1981) and chlorophyll (1969–1984) and their spatial distribution in summer 1989 were studied in the Rybinsk reservoir (second largest reservoir of the Volga River, North-West Russia). Estimation of trophic status and saprobity of the reservoir was based on phytoplankton biomass and species composition and chlorophyll content. The most eutrophic waters were found to occupy the peripheral areas in littoral zone and river inflows of the reservoir, while the waters in the central part of the basin were less eutrophic. Long-term changes of the phytoplankton biomass, chlorophyll, chlorophyll/biomass-ratio and saprobity index observed in the central part of the reservoir were analyzed by statistical methods. An increase in saprobity and an inverse relationship between chlorophyll/biomass-ratio and water transparency demonstrate progressive eutrophication in the central part of the reservoir. Two distinct periods (1954–1970 and 1971–1984) could be discerned on the basis of annual mean phytoplankton biomass values. For the earlier period a relationship between biomass and climatic factors (solar radiation and wind velocity) could be established, but no such correlation could be found for the latter period. There was no significant increase in the phytoplankton biomass during the monitoring period, but a definite increase in the proportion of small-sized species of centric diatoms, cryptomonads and blue-greens. These forms are considered as r-strategists in the community, and their increase is interpreted as a sign of eutrophication.     

A large reservoir as a source of zooplankton for the river: structure of the populations and influence of fish predation

Within an extensive programme on the Seine river, including the large reservoirs in the upstream basin, zooplankton populations were investigated at the reservoir-river interface to find out their fate when released into the river. Zooplankton structure, abundance and biomass were analysed in the river upstream and downstream from the reservoir, in the release canal and in the reservoir. Whereas the river zooplankton are dominated by rotifers, microcrustaceans represent a large part of the population in the reservoir, because of the longer residence time (6 months). We have shown that the reservoir is a source of zooplankton; we calculated a biomass export of 30-60 tons C year^-1, which is, however, rapidly lost in the river. One of the main loss factors was found to be selective fish predation on larger zooplankton species developed in the reservoir.      

Taxonomic composition and abundance of macrozoobenthos in the Rybinsk Reservoir at the beginning of the 21st century

The structure of macrozoobenthos has been studied in the deep-water part of the Rybinsk Reservoir. A total of 73 species of bottom macroinvertebrates have been recorded, the majority of which are mollusks, oligochaetes, and chironomids. The macrozoobenthos on gray silts of channel parts of the reservoir was the richest in taxonomic composition and quantitative abundance. The maximum number of species has been recorded in the former mouth of the Mologa River, and the highest abundance of macrozoobenthos has been recorded near the village of Breitovo in June. Most of the macrozoobenthos is made up of oligochaetes and chironomid larvae; midge larvae dominate by biomass. Compared to the end of the 20th century, changes in the taxonomic composition and in dominating species of macrozoobenthos are observed.     

Species-specific phytoplankton responses to nutrients and zooplankton manipulations in enclosure experiments

1. In situ enclosure experiments were performed in the mesotrophic Bermejales reservoir to evaluate the algal response to changes in the nutrient supply and in the zooplankton size structure and density in a 2 × 2 factorial design. The experiments were conducted during the spring bloom of nanoplanktonic diatoms in 1989. 2. Nutrient enrichment promoted a great increase of phytoplankton biomass indicating a strong nutrient limitation on phytoplankton growth. Total phytoplankton biomass was significantly lower in the Daphina-added enclosures at a given nutrient level and strong direct an indirect effect of zooplankton on phytoplankton community structure and nutrient availability were observed. 3. Most of the nanoplanktonic species were effectively grazed but species with protective coverings and large size colonies were favoured by grazers and small chlorococcales were unaffected probably because of their compensatory high growth rates. The decrease in total biomass imposed by grazers is attributable mainly to the decrease of Cyclotella ocellata, the most abundant species. This taxon suffers two net effects of zooplankton: direct grazing and the indirect decrease of Si availability caused by the growth of C. ocellata which was promoted by P excretion by zooplankton. Indirect effects of grazers on Si availability should, therefore, be taken into account in explaining phytoplankton succession and community structure. 4. In this experiment grazers affected considerably the nanoplanktonic community in Bermejales reservoir. The extent which they were affected, however, depended not only on the algal size as a determinant of edibility but also greatly on the specific nutrient requirements and taxonomic features of the algal species.     

Features of the structure and spatial distribution of plankton in the Sheksna Reservoir

Based on the field studies conducted in August 2005 and 2007, the distributions of zooplankton structure and abundance, as well as chlorophyll content, in the Sheksna Reservoir are analyzed. A total of 107 zooplankton species have been found (46 Cladocera, 18 Copepoda, and 43 Rotifera), including 24 species (10 Cladocera, 2 Copepoda, and 12 Rotifera) new for the reservoir. In the surface layer of water, where blue-green algae concentrate, zooplankton abundance and biomass are 1.5–5 times lower and the zooplankton structure is simpler than in deeper layers. The highest zooplankton biomass (>3 g/m³) are observed in Lake Beloe and the upper area of the Sheksna section, while in the near-shore sites it did not exceed 1 g/m³. There are no significant changes in zooplankton abundance when compared to the abundance recorded at the end of the past century.     

Short Term Effects of Tucuruí Dam (Amazonia, Brazil) on the Trophic Organization of Fish Communities

A dam on a river course induces numerous changes in the aquatic environment both in the newly formed reservoir and in the river downstream. These changes modify the food resources available to fishes. As a consequence, fish communities undergo rapid transformations particularly in terms of trophic organization. Tucuruí Dam, closed on the Tocantins River, Brazil, in September 1984, formed a large reservoir of approximately 2200km². Analyses of fish stomach contents were performed before and after the completion of the dam in the downstream section of the river as well as in the reservoir. Resource availability was seen through the relative contribution of food items in supporting the biomass. Main changes caused by the dam consisted of an increase in fishes as a food resource and of a parallel decrease of sediment both in the reservoir and in the downstream part of the river. In addition, in the downstream section, the relative contribution of plankton as a food resource diminished after dam closure. We identified 8 feeding regimes before dam closure. From them the trophic structure of fish communities were established and compared. Most of the community biomass was from specialist feeders. Contribution of piscivores increased after closure; planktivores became unimportant after closure downstream. Some species were shown to change their diet in the transformed environments either downstream or in the reservoir. However, these changes in individual species diet did not seem to play a major role in the transformation of trophic structure of the fish communities.     

清远水利枢纽建设对库区鱼类群落结构影响

清远水利枢纽是北江干流与珠江河口之间第一座枢纽,为探究清远水利枢纽建坝筑库后库区鱼类群落结构特征及变化,于2017—2018年在清远水利枢纽至飞来峡水利枢纽库区进行渔业资源调查,共采集鱼类49种,隶属于6目16科44属,以鲤(Cyprinus carpio)、鲮(Cirrhina molitorella)、赤眼鳟(Sq...     

Long term changes of biodiversity of benthic macroalgae in the intertidal zone of the Nanji Islands

A long term observation on biodiversity and biomass of benthic macroalgae in Point 1 of the intertidal zone of the Nanji Islands, Zhejiang were carried out during 1959–2007, including three phases, i.e. 1959–1965, 1980–1985 and 2000–2007. The results show that the species of the benthic macroalgae there disappeared by 41.7%, and decreasing trend of the biodiversity has been getting quick; the community structure clearly shifted, i.e. the proportion of subtropical and warm-temperate species increased, and that of cold-temperate species decreased in the benthic macroalgae assemblage, particularly the calcareous nullipore became an absolutely dominant group. In comparison with the second phase (1980–1985), during the third phase the average annual biomass of the benthic macroalgae decreased by 52.5%; the average spring and winter biomass decreased by 54.1% and 87.2%; while the average summer and autumn biomass increased by 11.1% and 3.2%, respectively. The causes of the decrease in the biodiversity have been discussed, and the authors considered that the climate change and increase in CO₂ concentration have been the main reasons to lead berserk growth of the nullipore, resulting in desertification tendency of the intertidal zone of the Nanji Islands.     

Zooplankton of the Argazi reservoir (Southern Urals, Russia) and its long-term changes

The Argazi reservoir on the Miass River, the oldest reservoir in the Southern Urals, has been investigated. In total 49 species and forms of zooplankton are identified, including new and rare species for the fauna of the Urals. Throughout the reservoir zooplankton has high species diversity and considerable biomass (up to 11 g/m³). Rotifers are the leading group in the plankton of the reservoir. Compared to the early 1960s, the abundance and biomass of zooplankton has increased by 5–10 times. The disappearance of some plankton forms and the emergence of new ones, as well as an increased number of rotifers and some crustaceans by 1–2 orders of magnitude, are noted. The influence of three main factors that could lead to long-term changes in zooplankton—eutrophication, heavy metals pollution, and global warming—are considered. The last factor seems to be the most important.     

Monitoring of the chitinolytic microbial complex of the phylloplane

A comprehensive study of chitinolytic microbial complexes of the phylloplane from cultured and forest plants has been conducted. An increase of the number and biomass of metabolically active cells of the representatives of the domain Bacteria and a decrease in fungal biomass in the experimental microcosms have been shown to occur after the introduction of chitin. The characteristic features of the taxonomic structure of metabolically active chitinolytic complexes of the phylloplane of the plants studied have been elucidated. Representatives of the phyla Proteobacteria, Bacteroidetes, and Verrucomicrobia have been shown to play important roles in the chitinolytic complexes of green leaf samples, while mycelial actinobacteria of the phylum Actinobacyteria played a similar role in needles of coniferous trees. A collection of chitinolytic microorganism cultures isolated from the phylloplane of different plant species has been created.     

Structure and functioning of the microbial loop in a boreal reservoir

The abundance and biomass of the main components of the microbial plankton food web (“microbial loop”)—heterotrophic bacteria, phototrophic picoplankton and nanoplankton, heterotrophic nanoflagellates, ciliates and viruses, production of phytoplankton and bacterioplankton, bacterivory of nanoflagellates, bacterial lysis by viruses, and the species composition of protists—have been determined in summer time in the Sheksna Reservoir (the Upper Volga basin). A total of 34 species of heterotrophic nanoflagellates from 15 taxa and 15 species of ciliates from 4 classes are identified. In different parts of the reservoir, the biomass of the microbial community varies from 26.2 to 64.3% (on average 45.5%) of the total plankton biomass. Heterotrophic bacteria are the main component of the microbial community, averaging 63.9% of the total microbial biomass. They are the second (after the phytoplankton) component of the plankton and contribute on average 28.6% to the plankton biomass. The high ratio of the production of heterotrophic bacteria to the production of phytoplankton indicates the important role of bacteria, which transfer carbon of allochthonous dissolved organic substances to a food web of the reservoir.     

Do the effects of piscivorous largemouth bass cascade to the plankton?

Ecologists have hypothesized that an increase in the biomass of piscivorous fish in lakes will cause a decrease in populations of planktivorous fish, an increase in the size of herbivorous zooplankton and a decrease in the biomass of phytoplankton. Here we present an experimental test of whether the effects of largemouth bass (Micropterus salmoides) cascade to the planktivorous fish, zooplankton and phytoplankton of a 15-ha water storage reservoir. A pilot study indicated that the reservoir was eutrophic with dense populations of planktivorous fish dominated by threadfin shad (Dorosoma petenense). No piscovorous fish were present in the reservoir. We conducted a one-month mesocosm experiment using water and plankton from the reservoir showing that the presence of threadfin shad reduced large-sized zooplankton and increased the productivity and biomass of phytoplankton. To test whether the effects of piscivorous fish could cascade to the plankton, we assessed the effects of the addition of piscivorous largemouth bass on the planktivorous fish, zooplankton and biomass of phytoplankton of the reservoir by monitoring the reservoir during the year before and the two years after largemouth bass were stocked. In the second year after the addition of largemouth bass, the number of planktivorous fish decreased and the relative abundance of threadfin shad declined. Although the abundance of cladocerans increased after the addition of largemouth bass, the average size of zooplankton did not change. We did not detect changes in chlorophyll a, Secchi depth, or concentrations of total phosphorus and total nitrogen as a result of the addition of largemouth bass.     

Kinetics of zooplankton in an aquatic continuum: from the Marne River and reservoir to the Seine estuary

A study was carried out within a 700-km river sector, including three types of ecosystems (a reservoir, a river and its estuary) to characterise the major features of zooplankton communities in the Seine Basin. In rivers, zooplankton biomass becomes significant only when the growth rate of the organisms is higher than the dilution rate (4-5th orders rivers, according to River Continuum Concept). Upstream, short residence times favour the development of small species (Rotifers) with low individual body weight and biomass. Conversely, larger species (microcrustaceans) develop more downstream, where increased residence time leads to autochthonous production (Riverine Productivity Model). Such a pattern is greatly modified by human impact. Zooplankton input from the Marne reservoir represents one type of disruption in the general upstream-downstream trend (according to the Serial Discontinuity Concept). This reservoir is a source of microcrustaceans; they rapidly disappear mainly through fish predation, and therefore have little impact on the river phytoplankton. Discontinuities, such as confluences, have a relatively small effect on the stock of zooplankton with regard to the water release from the reservoir, but they persist more downstream, because they have the same lotic origin. A few microhabitats with macrophytes play a small role for this canalised river, but they can modify locally the plankton community structure and composition. As a whole, the flux of zooplankton rises exponentially, whereas discharge increases linearly from upstream (4th order) to downstream (8th order). In the canalised sectors, Dreissena larvae build up an important biomass, adding to that of the zooplankton sensu stricto. Especially abundant in the downstream sector of the Marne and Seine Rivers, the larvae show a widespread colonisation of the benthic substrates by the adult Dreissena. One of the largest mussel colonies in the middle estuary can contribute to a rapid decrease of zooplankton. Estuary ecosystems form a transitional zone between freshwater and seawater, with zooplankton dynamics closely linked to the particular conditions on this part of the river system.     

The effect of different fish communities on the cladoceran plankton assemblages of the Kis-Balaton Reservoir,Hungary

In 1995 the authors studied the effect of differentfish communities on the structure of the cladoceranplankton in a shallow hypertrophic lake. After a fishkill of 1991, different fish communities developedin the Kazetta and the outer area of the Kis-Balatonreservoir. In the outer area of the reservoir, thedensities of plankton feeding fish species wereconsiderably higher than in the Kazetta. Thesedifferences induced changes in the structure anddynamics of the cladoceran plankton. The biomass ofsmall-bodied cladocerans (mainly Bosmina longispina)was higher and the biomass of the large-bodiedcladocerans (D. hyalina, D. magna) was lower in thewestern and eastern part of Kis-Balaton reservoir thanin the Kazetta. A peak in cladoceran biomass in theKis-Balaton reservoir was observed during the summer,close or during a bloom of filamentous cyanobacteria,whereas in the Kazetta a peak was observed during thespring, before the bloom of cyanobacteria. The adultfemales of D. hyalina were larger and produced moreeggs in the Kazetta than in the outer area of thereservoir.     

Spatial and temporal variation in phytoplankton community structure in a southeastern U.S. reservoir determined by HPLC and light microscopy

Spatial and temporal variation in phytoplankton community structure within a large flood-control reservoir (Sardis Reservoir, MS, USA) was investigated in relation to variation in physicochemical properties, location within the reservoir, hydraulic residence time (HRT), nutrient concentrations, temperature, and light conditions over a 14-month period. During periods of short HRT, phytoplankton communities throughout the reservoir were homogeneous in biomass, composition, and production. With a gradual increase in HRT from spring to summer, spatially heterogeneous phytoplankton communities developed along the longitudinal axis of the reservoir. During this period of longer HRT, diatoms and chlorophytes were a larger proportion of total phytoplankton biomass at shallow and more turbid locations near the head of the reservoir, whereas cyanobacteria were a larger proportion of the community at deeper and less turbid locations closer to the outflow. Seasonal succession of the phytoplankton community was represented by high abundance of diatoms in spring, increasing biomass of cyanobacteria through summer, and a secondary bloom of diatoms in fall. Species of Cyclotella, Asterionella, Nitzschia, and Ankistrodesmus were among the first colonizers in the early growing season, closely followed by Aulacoseira, whereas species of Staurastrum and Tetraedron appeared later in the spring. Species of Synedra, Crucigenia, Selenastrum, Scenedesmus, and Merismopedia occurred throughout the sampling period. As the diatoms started to decrease during mid-spring, cryptophytes increased, prior to dominance of species of Pseudanabaena in summer. Reservoir management of HRT, in combination with spatial variation in reservoir morphology and seasonal variation in temperature and riverine nutrient inputs, creates seasonally variable yet distinct spatial patterns in phytoplankton community biomass, composition, and production. Handling editor: L. Naselli-Flores     

Non-native prey species supporting fish assemblage biomass in a Neotropical reservoir

The present study aimed to investigate the role of four non-native invertebrates in supporting fish biomass as well as their influence on the carbon flow into the Volta Grande reservoir food web. The fish samples were carried out quarterly between October 2015 and July 2016 using gillnets. At the sampled sites, four non-native invertebrates (golden mussel, Asian clam, trumpet snail and Amazonian prawn), which are potential prey for fish in the Volta Grande reservoir, were collected by targeted sampling using a Petersen-type bottom dredger and semi-circular sieves. The gut contents of the fish were collected and analyzed under stereoscope, and samples of muscle tissue of these fish, as well as the four non-native invertebrate species sampled, were submitted for isotopic analysis. Results obtained by the present study, by both gut content and stable isotopic analyses, pointed to a trophic structure where non-native species represent not only a strong component of the fish community, but also their main carbon source. Based on gut contents and isotopic mixing models, we found that together, non-native prey are essential carbon sources for the fish fauna, fuelling more than 40.0% of the biomass in four dominant fish species. The consumption rate of non-native bivalves by the native omnivorous fish Leporinus friderici suggested these filter-feeding organisms potentially constitute an important trophic connection between littoral consumers and pelagic energy sources. In addition, non-native prey were also prominent carbon sources for non-native fish, fuelling more than half of the biomass in peacock bass and silver croaker, suggesting these prey have a fundamental role in maintaining non-native fish populations in this system. Our results may help to understand fundamental ecological issues bringing to light the extent to which these new combinations of species influence the energy flow and ecosystem properties of the Volta Grande reservoir.

     

Heterotrophic nanoflagellates in water column and bottom sediments of the Rybinsk Reservoir: Species composition,abundance, biomass and their grazing impact on bacteria

Abundance, biomass, and taxonomic composition of heterotrophic nanoflagellates (HNFs) have been determined in the water column and bottom sediments of the large lowland meso-eutrophic reservoir (Rybinsk Reservoir, Upper Volga) in summer. The role of HNFs in the consumption of the bacterial production is estimated. In the reservoir, 55 species from 15 large taxa, including 35 species from the plankton, are identified and 45 species are from benthos samples. The orders Kinetoplastida, Choanomonada, and Chrysomonadida are distinguished by the highest species diversity. Abundance and biomass of HNFs in the water column average 991 ± 326 cells/mL and 41.4 ± 14.1 mg/m³, while in the bottom sediments they are (236 ± 61) × 10³ cells/mL and 10.7 ± 4.0 μg/mL, respectively. The biomass of HNFs average 11.2% of the bacterial biomass in the water column and only 0.8% of that in the sediments. Flagellates are found to be a major factor which control the development of bacterioplankton grazing, on average, 32.3% of its daily production, whereas their impact on bacteriobenthos is insignificant, as they consume, on average, only 2.0% of its production.     

Population structure and spatial distribution of <Emphasis Type="Italic">Gmelinoides fasciatus</Emphasis> (Stebb.) in the cooling reservoir of the Belovo Thermal Power Plant

The sex ratio and size-age structure of the Gmelinoides fasciatus (Stebb.) population in different areas of the cooling reservoir of the Belovo Thermal Power Plant (Kemerovo oblast) has been analyzed. The highest values of abundance and biomass of the species were recorded in areas with the lowest heating and lowest temperatures of the natural thermal regime. The invasion of G. fasciatus in the Belovo Reservoir has not caused the extinction of the indigenous species Gammarus lacustris Sars.     

洋河水库浮游植物组成及优势种演替规律研究

在洋河水库设置6个采样点, 对浮游植物进行了周年研究, 并在夏季进行了每周一次的加密采样, 以揭示水华期间藻类优势种演替规律。结果表明洋河水库全年共检测到浮游植物8门41属49种, 群落季节变化与温度密切相关。春季隐藻门的啮齿隐藻(Cryptomonas erosa)为优势, 夏季初期表层水温在25℃以下时, 绿藻门的波吉卵囊藻(Oocystis borgei)占主要优势; 当表层水温升至25℃以上, 微囊藻(Microcystis spp.)迅速取代其成为绝对优势。秋季硅藻门的克洛脆杆藻(Fragiaria crotomensis)和隐藻门的啮齿隐藻(C. erosa)为优势。空间分布上水库北部浅水区域隐藻和硅藻生物量普遍高于南部; 受东南风影响, 蓝藻生物量在西洋河口S2点位最大。CCA分析表明夏季水华主体微囊藻的生物量与氮浓度正相关, 螺旋鱼腥藻在夏季仅作为第二优势种短暂出现于西洋河口处, 其出现与否受到磷营养盐的限制。