Current status and future tendency of lake eutrophication in China

Current trophic status and trend of Chinese freshwater lakes were investigated in this study. The results showed that all lakes studied were commonly undergoing the eutrophication process, water quality decreased and lake’s ecosystem is being declined. Most of the urban lakes are facing serious eutrophication. Many medium-sized lakes are in metrophic or eutrophic status, some local water are even approaching the hypertrophic level. The famous five freshwater lakes in China have entered into eutrophication in the condition of higher nutrient load. Lake Taihu, Hongze and Caohu are already in eutrophic state. Eutrophic lakes are mainly distributed in the middle and lower reaches of Yangtze River and Yungui plateau. Lake eutrophication developed rapidly. Among the 34 lakes studied in 1970’s, most of lakes were in the mesotrophic status, mesotrophic water area accounted for 91.8%. With the nine year of 1978–1987 the area percentage of oligotrophic lakes decreased from 3.2% to 0.53%, and that of eutrophic lakes increased from 5.0% to 55.01%. Recent data showed 57.5% lakes were in eutrophic and hypertrophic status of the 40 surveyed lakes.

Eutrophic trend of Lake Taihu, Chaohu and Xuanwu in the region of the middle and lower reaches of Yangtze River was predicated using the ecological stress model. The results showed that in 2008 Lake Taihu, Chaohu and Xuanwu might be of eutrophication, eutrophication and hypertrophication, respectively if no control measurement is taken. Provided the pollution water treatment rate is 60% in 2030, approximately 30 billion ton pollution water would still be discharged directly in the lakes. Therefore, in 2030 the urban lakes in China might be eutrophication or hypertrophication, and most of the medium-sized lakes at the urban-rural fringe might be in eutrophication or hypertrophication. The famous five biggest freshwater lakes in China might be eutrophication if control countermeasures are taken as now.

Lake eutrophication has become a serious environmental problem in China. Based on the domestic and foreign experiences of the eutrophic control technologies, both nutrient pollution control and lake ecological restoration should be carried out and this may be the guidance for the eutrophic control of lakes in China.

     

Molecular Existence and Diversity of Nitrite-Dependent Anaerobic Methane Oxidizing (n-Damo) Bacteria in the Lakes of Badain of the Gobi Desert

Nitrite-dependent anaerobic methane oxidation (n-damo) process, mediated by Candidatus Methylomirabilis oxyfera of the candidate phylum NC10, was discovered recently which plays an important role in coupling the global nitrogen and carbon cycles. However, the distribution and diversity of this new anaerobic methane-oxidizing microorganism have not been investigated in desert lakes yet. The present study successfully retrieved n-damo bacterial 16S rRNA and pmoA gene sequences using PCR technique from lakes in Badain Jaran Desert of China. Phylogenetic analyses showed that n-damo bacteria widely occurred in brine and freshwater lakes on the desert with high diversity, including both sediment and water samples. The results of quantitative PCR indicated that the abundance of the 16S rRNA gene in lake sediments varied from 1.12?±?0.68?×?10⁵ to 1.64?±?0.70?×?10⁵ copies g^?1 (dry weight), while that in water samples per milliliter was generally one order of magnitude lower than sediments. Correlation analyses suggested that n-damo bacterial abundance and diversity strongly depended on salinity. In lake sediments, the distribution, abundance, and diversity of n-damo bacteria were significantly associated with depth due to the concentration gradient of the NO_x^- and ammonium. This study provided new insights into both the n-damo community patterns and its interaction with ambient environmental factors in the desert lake ecosystem.     

Relation between nematode communities and trophic state in southern Swedish lakes

The aim of this study was to examine whether littoral nematode community patterns are shaped by lake trophic state. It was hypothesized that trophic level is associated negatively with the proportion of omnivores and positively with the percentages of bacterial feeders, but not at all with the diversity, abundance, and biomass of freshwater nematodes. Sediment samples were taken at littoral sites of eight southern Swedish lakes of different trophy in spring and autumn 2007. Trophic level was found to strongly influence species richness, as oligotrophic and mesotrophic lakes supported the greatest species numbers, whereas nematode abundance, biomass, and Shannon index were unaffected. Furthermore, our results indicated effects on the nematode community’s trophic structure, with a larger proportion of predatory nematodes in oligotrophic and mesotrophic lakes but no differences in the other feeding types (bacteria, algae and suction feeders, omnivorous species). Multivariate analysis indicated a shift in species compositions along the threshold from mesotrophic to eutrophic conditions, with the presence of Tobrilus gracilis, Monhystera paludicola, Brevitobrilus stefanskii, and Ethmolaimus pratensis related to the latter. Nematode communities in oligotrophic and mesotrophic lakes were characterized by a similar species composition, with pronounced occurrences of Eumonhystera longicaudatula, Semitobrilus cf. pellucidus, Prodesmodora circulata, and Rhabdolaimus terrestris. Overall, the results suggested that lake trophic state is a major factor structuring littoral nematode communities, although intra-lake variations might be of importance as well.     

Diatom community succession in the recent history of a eutrophic Yunnan Plateau lake, Lake Dianchi, in subtropical China

Fish introduction, eutrophication and disappearance of aquatic vegetation are important disturbances of aquatic ecosystems, especially in plateau lakes, which are generally considered to be very vulnerable. Fish were introduced to Lake Dianchi, a eutrophic plateau lake in southwest China, in the late 1950s and 1970s. After the introduction, invasive fish became the dominant species, and the total fish yield increased. Meanwhile, the trophic level of Lake Dianchi had a tendency to increase in the past decades because of the increases in human activities in the watershed area. In addition, the area of aquatic vegetation decreased from more than 90 to 1.8% of the lake area from the 1950s to 2000. This study investigated the effects of fish introduction, eutrophication and aquatic vegetation on the diatom community of Lake Dianchi by examining the changes of microfossil diatom assemblage and abundance. Results showed that the absolute abundance and diatom assemblages changed after fish were introduced. The endemic species, Cyclotella rohomboideo-elliptica, disappeared with the introduction of fish and increasing trophic levels after 1958. Fragilaria crotonensis entered into the lake with the introduction of fish and gradually thrived in the lake after 1958. Diatom species numbers also decreased gradually from 21 to 9 from the past to present. Epiphytic diatoms disappeared with the decrease of aquatic vegetation after 1985. Our study indicated that eutrophication was the most important process determining diatom abundance, and fish introduction was a secondary process determining diatom abundance, while aquatic vegetation had a more important role in structuring the diatom community in this eutrophic plateau lake.     

Bacterial Diversity and Geochemical Profiles in Sediments from Eutrophic Azorean Lakes

In the Azores, the advanced trophic state of the lakes requires a fast intervention to achieve the good ecological status prescribed by the Water Framework Directive. Despite the considerable effort made to describe the phytoplankton growing on the water column, the lack of information regarding the microbial processes in sediments is still high. Thus, for the successful implementation of internal management actions, the present work explored the relationships between geochemical profiles and dominant members of the bacterial community in sediments from eutrophic Azorean lakes. Lake Azul geochemical profiles were quite homogeneous for all parameters, while in lake Furnas the total iron profile presented a peak below the aerobic layer. For lake Verde, the concentrations of all studied parameters (20 ± 2% loss-on-ignition; 2.10 ± 0.08 mg g^?1 total phosphorus; 1.31 ± 0.50 mg g^?1 total nitrogen; 8.06 ± 0.13 mg g^?1 total iron) in the uppermost sediment layer were approximately two times higher than the ones in sediments from other lakes, decreasing with sediment depth. The higher amounts of phosphorus and organic matter in lake Verde suggested a higher internal contribution of phosphorus to eutrophication. The dominant members of the sediment bacterial community, investigated by denaturing gradient gel electrophoresis, were mostly affiliated to Proteobacteria phylum (Alpha-, Delta-, and Gamma-subclasses), group Bacteroidetes/Chlorobi and phylum Chloroflexi. The Cyanobacteria phylum was solely detected in sediments from lake Verde and lake Furnas that presented the highest amounts of nitrogen and phosphorus both in the water column and sediments, while the other phyla were detected in sediments from the three studied lakes. In conclusion, management measurers to achieve the good ecological status until 2015 should be distinct for the different lakes taking into account the relative magnitude of the nutrient sources and the bacterial diversity in sediments.     

Copepod communities in karstic mediterranean lakes along the eastern Adriatic coast

The copepod communities of karstic lakes along the eastern Adriatic coast were studied. Lakes were divided in several groups according to their morphology (deep, shallow, barrage and reservoirs), production (oligotrophic, mesotophic and eutrophic), and salinity of water: freshwater and brackish. Copidodiaptomus steueri, Eucyclops serrulatusand Macrocyclops albidus belong to the group that inhabited most of the lakes under the study, regardless of lake type. The shallow karstic lakes are usually inhabited by Thermocyclops dybowskii, T. oithonoides, Cyclops vicinus and Eudiaptomus padanus etruscus in freshwater biotopes, and Calanipedia aquaedulcis and Copidodiaptomus steueri in brackish biotopes. The last two species can also be found in deep karstic lakes with brackish water (Bacina lakes in the Neretva River delta). Species like Cyclops abyssorumcan be found in most deep freshwater lakes. Some Calanoida were recorded in only one lake, like Eudiaptomus transsylvanicusin the deep Lake Vrana on the island of Cres, or Eudiaptomus hadzici in the barrage Lake Visovac. Production of the lakes, expressed as copepod biomass, depends on lake trophy, and in some lakes also on hydrology and salinity. Most of the meso-eutrophic lakes in the study area had Calanoida dominating, while Cyclopoida dominated in some oligotrophic and eutrophic lakes as well.     

Eutrophication as a driver of r‐selection traits in a freshwater fish

This study tested whether eutrophication could influence life‐history traits of a cyprinid, Chanodichthys erythropterus, in 10 Chinese lakes. Using the von Bertalanffy growth model, the asymptotic length (L_∞) and the growth performance index (I_GRO) were significantly affected by eutrophication. The gonado‐somatic index (I_G) and relative fecundity (F_R) were significantly lower in mesotrophic lakes than in eutrophic and hypertrophic lakes. These results indicate that increasing eutrophication affects the life‐history tactics of a freshwater fish.     

Differences in food webs and trophic states of Brazilian tropical humid and semi-arid shallow lakes: implications of climate change

Global warming may intensify eutrophication of shallow lakes by affecting nutrient loading, evaporation rates, and water level and thus produce major changes in food webs. We investigated to what degree food webs in tropical humid lakes differed from those in more eutrophic semi-arid lakes of the same latitude. Our results indicate that the catchment area-to-lake area ratio, nutrients, chlorophyll a, suspended solids, abundances of phytoplankton, zooplankton, and omnivorous fish as well as total fish catch per unit effort were all higher in the semi-arid lakes, whereas inlet water-to-evaporation ratio (proxy for water balance), water transparency, percentage macrophytes cover, and the piscivores:omnivores ratio were higher in the humid lakes. Our results suggest that reduced inlet water-to-evaporation ratio will increase lake eutrophication, which, in turn, as in temperate regions, will alter trophic structure of the freshwater community.

     

Functional shifts in lake zooplankton communities with hypereutrophication

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Ecological sensitivity of marl lakes to nutrient enrichment: evidence from Hawes Water,UK

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Comparing Alkaline Phosphatase PhoX-Encoding Genes in Two Contrasting Habitats of the Large Eutrophic Lake Taihu,China

River mouth areas of eutrophic lakes have frequent cyanobacterial blooms and high organophosphate mineralization rates. To determine the genetic background of the high organophosphate mineralization rate in river mouth areas of eutrophic lakes, we compared the diversity and abundance of bacterial alkaline phosphatase PhoX-encoding genes in the river mouth areas and the lake center within the large eutrophic Lake Taihu, China. Results showed that the seasonal average values of phosphorus content, bacterial alkaline phosphatase activity, diversity, and abundance of bacterial phoX in the river mouths were significantly higher than those in the lake center, and 47% of all identified genotypes were present only in the river mouths. The genotypes most similar to alphaproteobacterial phoX dominated in both regions, with 72% and 64% of the total genotypes in the lake center and river mouths, respectively. More than 40% of the total phoX genotypes were only found in the river mouths, however, indicating the special microbial nature in this hypereutrophic habitat. The differences in contents of dissolved organic carbon and phosphorus were related to the divergences of bacterial phoX genotypes in these two contrasting habitats. Because some dominant genotypes most similar to phoX genes of alphaproteobacterial genus were observed only in the river mouth areas, such as Microvirga sp. WSM3557, and because the hydraulic retention time of Lake Taihu is insufficient to shape the special bacterial groups in the river mouths, allochthonous inputs of nutrients and bacterial species could make contributions to explain the different organophosphate mineralization rates in these two contrasting habitats of the large eutrophic lake.     

Phototrophic Picoplankton in Temperate Lakes: Seasonal Abundance and Importance along a Trophic Gradient

The seasonal development of autotrophic picoplankton was investigated in seven Danish lakes representing a eutrophication gradient. Highest cell abundance between 1.5 to 6 × 10⁵ cells ml⁻¹ were found in mid-summer. Minor peaks were observed in spring. In winter, densities were below 10³ ml⁻¹. The highest relative picoplankton contribution to total autotrophic biomass also occurred in mid-summer. In the eutrophic lakes and one humic lake the average seasonal contribution of picoplankton to total chlorophyll was below 1% increasing to 5-8% in the meso- and oligotrophic clear water lakes. During short periods the proportion of picoplankton did reach 25%. The higher relative importance of picoplankton in less productive lakes was not due to higher actual chlorophyll concentrations, but due to a much more pronounced response by larger algae at higher nutrient loading. Both cyanobacteria and eukaryote organisms were present as picoplankton. Only eukaryotes were found in one eutrophic lake and an acidic, humic lake. In the eutrophic lakes eukaryote picoplankton was dominant; both with respect to cell densities and biovolume, whereas cyanobacteria dominated the two meso-oligotrophic lakes. Autotrophic picoplankton were present in all lake types, however their importance seemed to be less in most eutrophic lakes than in less productive, meso-oligotrophic lakes.     

Quantitative analysis of freshwater ostracode assemblages in southwestern Yukon Territory,Canada

Relations between modern ostracode assemblages and environmental variables from lakes in the southwest Yukon and northern British Columbia were explored. A total of 29 freshwater species representing 8 genera were identified from the sediments of 36 lakes, with the number of species ranging between 3 and 8 per lake. Species widespread throughout the study area include Cyclocypris ampla, Candona candida, Cypria turneri, Cypria ophtalmica, and Candona protzi. The Mg/Ca ratio is an important factor determining the ostracode species composition of a lake. Species richness is at a maximum when the lake water has intermediate values of conductivity. Lakes in which one species clearly dominates the assemblage (‰>‰70% relative abundance) have water saturated with respect to CaCO₃. Mg/Ca ratio, depth and Sr are the environmental factors that are most highly correlated with species distributions in this region.     

Analysis of the community structure of planktonic ciliated protozoa relative to trophic state in Florida lakes

The planktonic ciliate populations of 30 Florida lakes constituting a broad trophic gradient were examined to determine the response of protozoan community structure to increasing eutrophication. Both ciliate abundance and biomass were strongly related to lake trophic state. Comparison of the Florida data base with a comparable north temperate lake group indicated that subtropical lakes generally possess higher ciliate abundance and biomass at a given trophic state than temperate lakes. However the equations derived for each data base were not significantly different. Community diversity and species richness increased with increasing lake productivity. Highly acidic lakes displayed significantly reduced diversity and numbers of species when contrasted with nonacidic oligotrophic lakes. Small-bodied (< 30 um) ciliates dominated all lakes but were proportionally less important in oligotrophic lakes. Presence-absence data produced three assemblages: an ubiquitous association of primarily small ciliate taxa, a group of large ciliates mainly restricted to eutrophic-hypereutrophic lakes, and a very large ciliate,Stentor niger, which dominated the protozoan communities of acidic oligotrophic lakes.     

Surface sediment diatom assemblages and epilimnetic total phosphorus in large, shallow lakes of the Yangtze floodplain: their relationships and implications for assessing long-term eutrophication

1. The Yangtze floodplain (SE China) is characterized by a number of large shallow lakes, many of which have undergone eutrophication due to the intensification of agriculture and urban growth over recent decades. As monitoring data are limited and in order to determine lake baseline nutrient concentrations, 49 lakes were sampled, covering a total phosphorus (TP) gradient (c. 30–550 μg L⁻¹) to develop a diatom-based inference model. 2. There are three dominant diatom assemblages in these shallow lakes with a marked change in assemblage structure near the boundary between eutrophic and hypereutrophic nutrient levels (as indicated by their TP value). Canonical correspondence analysis indicated that TP was the most important and significant variable in explaining the diatom distributions, independently accounting for 9.5% variance of diatoms. 3. Forty-three lakes were used to generate a transfer function using weighted averaging (WA) with inverse deshrinking. This model had low predictive error (root mean squared error of prediction; RMSEP_jack = 0.12) and a high coefficient of prediction (R²_jack = 0.82), comparable with regional TP models elsewhere. The good performance of this TP model may reflect the low abundance of benthic diatom species which are commonly regarded as the main error source in European shallow lake WA models. 4. The WA model was used to reconstruct the past-TP concentrations for Taibai Lake, a shallow hypereutrophic lake in Hubei province. The results showed that TP concentration varied slightly (43–62 μg L⁻¹) prior to the 1920s, indicating an eutrophic state since the 1800s. A period of sustained eutrophication occurred after 1950, because of the development of agriculture, reflecting by maximum values of Aulacoseira alpigena and increased abundance of Cyclotella meneghiniana, C. atomus and Cyclostephanos dubius. The steep increase in nutrient concentration after 1970 was related to the overuse of chemical fertilizer and fish farming in the catchment. 5. The shift in fossil diatoms from epiphytic to planktonic forms in the lake sediment core during 1950–70 provides useful information on the transformation from macrophyte-dominated to alga-dominated states. It is plausible that the TP concentration of 80–110 μg L⁻¹ observed in this study is the critical range for switching between the two stable states in the lake. 6. The regional diatom-TP model developed in this study allows, therefore, the possibility of reconstructing historical background nutrient concentrations in lakes. It will provide an indication of the onset and development of eutrophication at any site. This is particularly important for the many lakes in the Yangtze floodplain where information about historical changes in water quality is lacking.     

Differentiation of Nitrogen and Microbial Community in the Sediments from Lake Erhai,Yunnan–Kweichow Plateau,China

Abstract

As a famous plateau lake and a place rich in biodiversity located at the Hengduan Mountains, there is little research on microbial diversity and community composition in Erhai. In this study, 770,425 16S rRNA sequences had obtained at different depth samples. The abundance‐based coverage estimates (ACE), Chao1, and Shannon indices indicated the high abundance and diversity of Erhai sediment microorganisms. And they were obviously affected by human disturbance. Gammaproteobacteria, Deltaproteobacteria, Bacteroidia, Anaerolineae, Phycisphaerae, and Methanomicrobia were dominant bacteria and existed in almost all samples. The content of total nitrogen (TN) in sediments had a significant positive correlation between Syntrophus, Deltaproteobacteria, Desulfatiglans, Oxyphotobacteria, Clostridiales, Burkholderiaceae, Geobacter, Crenothrix species richness. Desulfobacca, Syntrophus, Deltaproteobacteria, Desulfatiglans, Gammaproteobacteria, Oxyphotobacteria, and Clostridiales were positively correlated with the nitrates in sediments. And the species richness of Desulfatiglans was correlated with NO₂ ^-. The RDA analysis was shown that dbRDA1 was affected mainly by the depth of lake, while the content of TN, NO₃ ^?, NO₂ ^?, and NH₄ ⁺ had the largest effect on dbRDA2. The results indicated the great relations between the diversity and composition of microbial communities and different forms of sediment nitrogen in Erhai lake sediments.     

Paleolimnological reconstruction of the trophic state in Lake Balaton (Hungary) using Cladocera remains

The sediment of Lake Balaton (Hungary) provides important information about the lake’s history, particularly with regard to eutrophication. In this study, we used fossil pigment analysis and subfossil Cladocera remains preserved in a dated sediment core to identify trophic stages from ~250 bc to present. Dates of the most recent eutrophic events are in good agreement with previously published data. In general, the abundance and diversity of the Cladocera community increased with eutrophication and decreased with oligotrophication. The sediments of Lake Balaton were characterised by Chydoridae remains, of which Alona species were the most abundant. Of these, Alona quadrangularis and Alona affinis accounted for 40 and 20% of the total Cladocera remains, respectively. The trophic state of Lake Balaton varied between mesotrophic and eutrophic regimes. Seven different trophic periods were identified in Lake Balaton on the basis of Sedimentary Pigment Degradation Unit (SPDU) content of the sediment. Eutrophic states were (1) from ~250 to ~30 bc, (3) between ~300 and ~590 ad, (5) between 1834 and 1944 and (7) from the 1960s until present. Mesotrophic states were (2) ~30 bc to ~300 ad, (4) 590–1834, (6) 1944–1960s. Discriminant analysis of the cladoceran data confirmed these historic events, except for the short mesotrophic episode between 1944 and 1960. The first stage of eutrophication of Lake Balaton (~250 to ~30 bc) was characterised by extensive macrophyte vegetation, as indicated by the increasing abundance of vegetation-associated Cladocera species (Eurycercus lamellatus, Sida crystallina, Pleuroxus sp.). Intensification of eutrophication was identified since the 1980s, reflected by a high abundance of Bosmina species. The most significant planktivorous fish of Lake Balaton was the Sabre carp (Pelecus cultratus), and when its number decreased, the abundance of Bosmina species increased. This study shows that Cladocera are responsive to trophic state changes, underlining their importance as a tool for the assessment of lake eutrophication.     

Current status and future tendency of lake eutrophication in China

Current trophic status and trend of Chinese freshwater lakes were investigated in this study. The results showed that all lakes studied were commonly undergoing the eutrophication process, water quality decreased and lake's ecosystem is being declined. Most of the urban lakes are facing serious eutrophication. Many medium-sized lakes are in metrophic or eutrophic status, some local water are even approaching the hypertrophic level. The famous five freshwater lakes in China have entered into eutrophication in the condition of higher nutrient load. Lake Taihu, Hongze and Caohu are already in eutrophic state. Eutrophic lakes are mainly distributed in the middle and lower reaches of Yangtze River and Yungui plateau. Lake eutrophication developed rapidly. Among the 34 lakes studied in 1970's, most of lakes were in the mesotrophic status,mesotrophic water area accounted for 91.8%. With the nine year of 1978-1987 the area percentage of oligotrophic lakes decreased from 3.2% to 0.53%, and that of eutrophic lakes increased from 5.0% to 55.01%. Recent data showed 57.5% lakes were in eutrophic and hypertrophic status of the 40 surveyed lakes.Eutrophic trend of Lake Taihu, Chaohu and Xuanwu in the region of the middle and lower reaches of Yangtze River was predicated using the ecological stress model. The results showed that in 2008 Lake Taihu, Chaohu and Xuanwu might be of eutrophication, eutrophication and hypertrophication, respectively if no control measurement is taken. Provided the pollution water treatment rate is 60% in 2030, approximately 30 billion ton pollution water would still be discharged directly in the lakes. Therefore, in 2030 the urban lakes in China might be eutrophication or hypertrophication, and most of the medium-sized lakes at the urban-rural fringe might be in eutrophication or hypertrophication. The famous five biggest freshwater lakes in China might be eutrophication if control countermeasures are taken as now.Lake eutrophication has become a serious environmental problem in China. Based on the domestic and foreign experiences of the eutrophic control technologies, both nutrient pollution control and lake ecological restoration should be carried out and this may be the guidance for the eutrophic control of lakes in China.     

Diversity of the major capsid genes (g23) of T4-like bacteriophages in the eutrophic Lake Kotokel in East Siberia, Russia

Numerous studies revealed high diversity of T4-like bacteriophages in various environments, but so far, little is known about T4-like virus diversity in freshwater bodies, particularly in eutrophic lakes. The present study was aimed at elucidating molecular diversity of T4-like bacteriophages in eutrophic Lake Kotokel located near Lake Baikal by partial sequencing of the major capsid genes (g23) of T4-like bacteriophages. The majority of g23 fragments from Lake Kotokel were most similar to those from freshwater lakes and paddy fields. Despite the proximity and direct water connection between Lake Kotokel and Lake Baikal, g23 sequence assemblages from two lakes were different. UniFrac analysis showed that uncultured T4-like viruses from Lake Kotokel tended to cluster with those from the distant lake of the same trophic status. This fact suggested that the trophic conditions affected the formation of viral populations, particularly of T4-like viruses, in freshwater environments.