Drivers of long‐term invertebrate community stability in changing Swedish lakes

Research on ecosystem stability has had a strong focus on local systems. However, environmental change often occurs slowly at broad spatial scales, which requires regional‐level assessments of long‐term stability. In this study, we assess the stability of macroinvertebrate communities across 105 lakes in the Swedish “lakescape.” Using a hierarchical mixed‐model approach, we first evaluate the environmental pressures affecting invertebrate communities in two ecoregions (north, south) using a 23 year time series (1995–2017) and then examine how a set of environmental and physical variables affect the stability of these communities. Results show that lake latitude, size, total phosphorus and alkalinity affect community composition in northern and southern lakes. We find that lake stability is affected by species richness and lake size in both ecoregions and alkalinity and total phosphorus in northern lakes. There is large heterogeneity in the patterns of community stability of individual lakes, but relationships between that stability and environmental drivers begin to emerge when the lakescape, composed of many discrete lakes, is the focal unit of study. The results of this study highlight that broad‐scale comparisons in combination with long time series are essential to understand the effects of environmental change on the stability of lake communities in space and time.     

Changes in community composition, carbon and nitrogen stable isotope signatures and feeding strategy in epilithic aquatic nematodes along a depth gradient

Periphyton is an important component within the littoral zones of lakes, but it is known to vary dramatically on small (cm–m) and large (km) spatial scales, showing differences in composition and abundance. Until relatively recently, changes in periphyton composition along depth gradients have not been studied sufficiently and the response of small meiobenthic invertebrates inhabiting the periphyton to vertically changing environmental conditions such as light are poorly understood. To investigate the changing community composition of epilithic (on stones) nematodes along a depth gradient, we conducted a field study at Lake Erken, Sweden, with the specific objective to investigate whether changes in periphyton composition (algae, bacteria) are reflected in changing nematode feeding types and what the consequences are for nematodes and their resource consumption. We analysed the abundance, species composition and feeding type distribution of epilithic nematodes along 11 depth levels, from 5 to 300?cm water depth. Our study resulted in the first measurements of carbon (¹³C) and nitrogen (¹⁵N) stable isotopes in free living nematodes in lakes. Nematode community composition and feeding type distribution exhibited dramatic changes along the depth gradient. Nematode feeding types changed from a dominance of algae-feeding species in the shallow littoral zone to one of bacteria-feeding species in the deep littoral zone. The ¹³C stable isotope signatures of nematodes and the small (<20?μm) periphyton fraction changed with increasing depth, with nematodes shown to feed on this small periphytic component. Nematodes were identified as primary consumers by means of trophic level calculations based on ¹⁵N stable isotopes.     

Associations and distribution of benthic nematodes in the Ethiopian Rift Valley lakes

The nematode associations in six Ethiopian rift lakes, one man-made lake, and three crater lakes were studied and related to water conductivity, lake depth and sediment particle size. The lakes investigated lie at moderate altitudes (1200–2000 m), are alkaline and vary in their conductivities. The rift lakes Abijata and Shala and the crater lakes Aranguadi, Kilotes and Chitu are soda lakes (K₂₅ > 6000 μS cm⁻¹), while the remaining five lakes and the man-made Lake Koka are within the freshwater range of conductivity (K₂₅ < 6000 μS cm⁻¹). A total of 16 species were identified including six new species. The nematode associations varied between lakes and were restricted to very few species in each lake. Most nematodes were restricted to non-saline lakes. The most dilute L. Zwai had a higher number of nematode species (12) and abundance than other lakes. The saline lakes Shala and Kilotes had nematode assemblages made up of only a single species (Mesodorylaimus macrospiculum). No nematodes were found in the hypersaline crater L. Chitu. Tobrilus africanus appeared more euryhaline than other nematodes occurring at conductivities as high as 15 000 μ S cm⁻¹ (L. Abijata). Five of the most common species (Dorylaimus sp., Monhystera stagnalis, Aphanolaimus tudoranceai, Tobrilus africanus and Actinolaimus perplexus) were associated with medium grained sand. A monthly variation in density of nematodes in L. Zwai is also shown.     

Environmental heterogeneity among lakes promotes hyper β‐diversity across phytoplankton communities

相似文献   

Patterns in the distribution of freshwater fishes in rivers of Central Western Ghats, India and their associations with environmental gradients

The community ecology of freshwater fishes in four river systems (Sharavati, Aghanashini, Bedti and Kali) of the central Western Ghats (India) has been studied for the first time. Patterns of fish species distributions were analysed and important stream and environmental parameters determining the species richness and composition of this region were identified. Upstream--downstream trends in species richness and diversity as well as changes in stream characteristics were studied using univariate correlation analyses. Preliminary analyses on changes in species composition and feeding guilds showed the presence of a gradual species turnover along the stream gradient. There were associated changes in the major feeding guild compositions, with a higher proportion of insectivore and algivore/herbivore composition in the upper reaches shifting to a predominance of omnivores and carnivores downstream. Pearsons product--moment correlation analyses along with stepwise multiple regression analyses identified stream depth and altitude as the important parameters determining species richness. Canonical correspondence analysis was performed to study species associations with environmental parameters. The analysis showed a strong species environmental correlation to the CCA axes, a high significance for the CCA axis 1 as well as for the overall test. The plots of the species and site scores on the CCA axes showed a clear segregation of species based on their relations with environmental and stream properties. This study is an important step in our understanding of the community structure of fish species of these rivers and would be helpful in future efforts on the conservation of aquatic communities and their habitats.     

The phytoplankton of some gravel-pit lakes in Spain

The phytoplankton communities of thirteen adjacent gravel-pit lakes in the lower Jarama river watershed (Madrid, Spain), were studied during spring mixing and summer stratification.If different seasons, the phytoplankton responded to different environmental factors. During spring, the abundance of SRP (soluble reactive phosphorus) and existence of a certain thermal stability resulted in the development of a greater biomass in some lakes. During summer, however, excessively high temperatures adversely affected the communities of the warmer lakes. At the species level, the responses were diverse; ordination techniques enabled us to group them.Some similarities were observed in phytoplankton composition between lakes, possibly due to local dispersion between adjacent lakes (frequented by abundant waterfowl).     

宜春温泉水体与泉底沉积物细菌多样性分析

研究宜春富硒温泉水体与泉底沉积物的细菌群落多样性。利用高通量测序技术分析泉水与沉积物中细菌群落结构与多样性。温泉水中主要的细菌类群为变形菌门和拟杆菌门,而在沉积物样品中的主要优势菌群为OP1、蓝细菌、浮霉菌门和绿弯菌门。细菌在属分类水平上,温泉水中优势菌群为不动杆菌属、假单胞菌属、水栖菌属、Thermosynechococcus、鞘脂杆菌属和金黄杆菌属等。沉积物样品细菌中优势菌群属于未知物种,在数据库中并没有相关的注释信息;其中已知的优势菌属为Candidatus acetothermum、Thermosynechococcus、亚热栖菌属、不动杆菌属。宜春温汤富硒温泉水体与沉积物中存在着丰富的微生物群落且组成差异性很大,该研究为了解与发掘温泉微生物菌种资源具有重要价值。     

苏州工业园区水体浮游甲壳动物群落特征及其与环境因子的关系

于2012年6月至2013年5月,对苏州工业园区湖泊和河流水体的浮游甲壳动物组成及群落结构进行了研究,分析了浮游甲壳动物的密度和生物量的年度变化,探讨其分布与水体理化因子间的关系.结果表明：园区水体有枝角类6科12属24种,桡足类7科13属18种,其中短尾秀体溞、长额象鼻溞、汤匙华哲水蚤及近邻剑水蚤在不同水体中不同季节均为优势种.在湖泊水体和河流水体中,浮游甲壳动物的密度和生物量表现为夏、秋季较高,冬、春季较低,且在夏、秋季分别具有2个峰值.枝角类平均密度和生物量在河流水体中均高于湖泊水体,两者间均具有显著差异;桡足类的平均密度在河流水体和湖泊水体间差异不显著,而平均生物量要显著高于湖泊水体.湖泊水体和河流水体在溶解氧、pH、透明度、总溶解固体、盐度、总磷、总氮及铵氮含量上均存在显著差异;冗余分析表明无论是湖泊水体还是河流水体,多数浮游甲壳动物的分布与水温、盐度、化学需氧量(COD_Mn)和总磷等指数呈正相关,只有枝角类中的溞属、船卵溞属种类的分布与水体溶解氧、pH值及透明度呈正相关.     

Assessing microbial diversity using recent lake sediments and estimations of spatio‐temporal diversity

Aim Recent papers have used large palaeolimnological datasets to reveal the biodiversity patterns of aquatic microorganisms. However, scant attention has been paid to the influence of time on these patterns. Where lake surficial sediment samples are used as integrals of diversity, the time interval of each sample varies according to differences in sediment accumulation rates. This paper aims to test the reliability of using lake surface sediments to measure and to compare microbial diversity when the potential influences of the species–time relationships are taken into account. Location Alpine lakes in Europe. Methods We analysed microorganism (siliceous microalgae) assemblages in three European Alpine lakes using short sediment cores (²¹⁰Pb‐dated) and annual sediment trap samples from 12 UK lakes. The same number of individuals was pooled for each sample 500 times to avoid sampling effort effects and to standardize species diversity estimation. The influence of time on the diversity score was assessed by simulating an increase of time span for surface sediment samples by cumulatively adding in successive sediment core samples (from the most recent to the oldest). We used species richness (S) and the exponential of the bias‐corrected Shannon entropy index (exp(H_b‐c)) to estimate diversity. Results Increasing the time interval represented by a surficial sediment sample did not affect the diversity results. The estimation of diversity was similar for cumulative and non‐cumulative samples. Diversity estimation was only altered in lakes experiencing high community turnover due to strong environmental forcing during the time period spanned by the cumulative sample. Main conclusions The use of surface lake sediments is suitable for estimating the average site diversity of free‐living microorganisms. Diversity is integrated in a single sample and species assemblage composition is derived from microbial communities living in distinct lake microhabitats. Species remains, accumulated in a single sample over several years of environmental variability, represent a diversity integral that captures a spatio‐temporal component equivalent to the γ‐diversity measure.     

Predicting diversity versus community composition of aquatic plants at the river scale

We tested the relative importance of physical versus chemical factors in explaining aquatic plant species diversity and community composition within a temperate lowland river. A total of 38 macrophyte species were identified at 33 sites along the 104 km length of the Rideau River, a National Heritage River of Canada. Species richness ranged from 0 to 15 species per site, and Shannon diversity from 0 to 2.98. Macrophyte species richness and Shannon diversity were significantly related to the physical characteristics of sites. For Shannon diversity, 77% of the increase was explained by an increase in sediment organic content and a decrease in water velocity. For species richness, 70% of the increase was explained by the latter factors in addition to an increase in the littoral zone (0–2 m depth contour) width and planktonic chlorophyll concentrations. River water chemistry did not explain any observed variation in either Shannon diversity or species richness in this moderately enriched system. In contrast to species richness, the physical and chemical variables measured failed to explain variation in community composition. Cluster analysis did not reveal any grouping of species into distinct communities. Canonical correlation analysis showed that environmental variables had minimal effect on the distribution of most species, with only floating-leaved species responding to water velocity. We conclude that physical factors can predict species diversity at the within river scale but not the species composition at a given site, underlying the need to preserve the geomorphological diversity of rivers to maintain plant diversity.     

The contribution of epipelon to total sediment microalgae in a shallow temperate eutrophic loch (Loch Leven, Scotland)

Benthic microalgae are known to perform important ecosystem functions in shallow lakes. As such it is important to understand the environmental variables responsible for regulating community structure, positioning and biomass. We tested the hypothesis that the positioning (across a depth gradient of 2–22 m overlying water depth) and relative biomass (determined using bulk and lens tissue harvested chlorophyll (Chl) a concentrations) of the epipelon community would vary independently with season (12 monthly samples) and across natural gradients of light and habitat disturbance relative to the total benthic algal community (i.e. all viable microalgae in the surface sediments) in a shallow eutrophic loch. Total sediment microalgal Chl a concentrations (TS-Chl; range: 5–874 μg Chl a g⁻¹ dw) were highest in winter and in the deepest site (20 m overlying water depth), apparently as a result of phytoplanktonic settling and sediment focussing processes. Epipelic Chl a concentrations (Epi-Chl; range: <0.10–6.0 μg Chl a g⁻¹ dw) were highest in winter/spring, a period when water clarity was highest and TS-Chl lowest. Principal components analysis highlighted strong associations between Epi-Chl and sites of intermediate depths (2.5–5.5 m) in all seasons except autumn/winter. Autumn/winter represented the season with the highest average wind speeds preceding sampling, during which the highest Epi-Chl concentrations were associated with the deepest sites. Epi-Chl was associated with intermediate light and habitat disturbance during spring/summer and summer/autumn and varied positively with habitat disturbance, only, in autumn/winter and winter/spring. The epipelon community structure also varied with depth; diatoms dominated shallow water sediments, cyanobacteria dominated deep water sediments, and sediments at sites of intermediate depth returned the highest biovolume estimates and the most diverse communities. This study has strengthened the hypothesis that the structure and biomass of benthic microalgal communities in lakes are regulated by habitat disturbance and water clarity, both of which are expected to respond to climate change and eutrophication. The degree to which these structural responses reflect functional performance requires clarification.     

Summer zooplankton in small rivers in relation to selected conditions

The abundance and the biodiversity of summer zooplankton in the waters of the Drawa drainage (NW Poland) were studied, as was their relation to selected environmental conditions. The conditions upstream, especially in the outlets of lakes, did not affect the zooplankton communities downstream. This was also true of tributaries which had no influence on the shape of the zooplankton communities in the main river. The number of zooplankton in the outlets of eutrophic lakes was greater than in those of mesotrophic lakes. Increased vegetation cover significantly affected mainly the crustacean communities of zooplankton. Larger amounts of zooplankton were observed in rivers where the riparian zone was not covered with vegetation, but this difference was not significant. The hydrological conditions of the rivers and the Secchi depth visibility strongly impacted the composition of the zooplankton. The influence of abiotic factors was most pronounced on the abundance of cladocerans, and least pronounced on the abundance of rotifers.     

Cladocera assemblages from the surface sediments of south-central Ontario (Canada) lakes and their relationships to measured environmental variables

Fossil cladoceran remains preserved in surface sediment samples from 44 oligotrophic lakes in south-central Ontario were examined to evaluate the relationships between species assemblages and measured environmental variables. Differences in cladoceran assemblages were related to physical and chemical variables using multivariate techniques. Redundancy Analysis (RDA) identified five environmental variables as significantly influencing assemblage composition: sulphate (SO₄²⁻), calcium (Ca²⁺), pH, maximum lake depth (Z _max) and dissolved organic carbon (DOC). There was a distinct separation of lakes and taxa along the ion gradient based on SO₄, Ca and pH. Additionally, cladoceran communities in coloured, shallow lakes had relatively higher abundances of littoral chydorid species and the pelagic taxa Holopedium spp., and the Daphnia pulex complex. Deep, clear lakes had relatively higher abundances of other pelagic taxa. Predation by fish (measured as presence–absence) and Chaoborus (measured as density) were less significant than some of the physico-chemical variables in influencing cladoceran assemblage structure. However, this could be due to the limited resolution of the predation data that was available at the time of this study. The distribution of cladocerans in the surface sediment, and their relation to these important environmental variables, suggests that there is considerable potential for the use of sedimentary cladoceran remains as environmental indicators in south-central Ontario lakes. Handling editor: J. Saros     

pH Influences the Importance of Niche-Related and Neutral Processes in Lacustrine Bacterioplankton Assembly

pH is an important factor that shapes the structure of bacterial communities. However, we have very limited information about the patterns and processes by which overall bacterioplankton communities assemble across wide pH gradients in natural freshwater lakes. Here, we used pyrosequencing to analyze the bacterioplankton communities in 25 discrete freshwater lakes in Denmark with pH levels ranging from 3.8 to 8.8. We found that pH was the key factor impacting lacustrine bacterioplankton community assembly. More acidic lakes imposed stronger environmental filtering, which decreased the richness and evenness of bacterioplankton operational taxonomic units (OTUs) and largely shifted community composition. Although environmental filtering was determined to be the most important determinant of bacterioplankton community assembly, the importance of neutral assembly processes must also be considered, notably in acidic lakes, where the species (OTU) diversity was low. We observed that the strong effect of environmental filtering in more acidic lakes was weakened by the enhanced relative importance of neutral community assembly, and bacterioplankton communities tended to be less phylogenetically clustered in more acidic lakes. In summary, we propose that pH is a major environmental determinant in freshwater lakes, regulating the relative importance and interplay between niche-related and neutral processes and shaping the patterns of freshwater lake bacterioplankton biodiversity.     

Cladocera paleocommunity to disentangle the impact of anthropogenic and climatic stressors on a deep subalpine lake ecosystem (Lake Iseo,Italy)

In big lakes with strong anthropogenic pressure, it is usually difficult to disentangle the impacts of climate variability from those driven by eutrophication. The present work aimed at the reconstruction of change in the species distribution and density of subfossil Cladocera in Lake Iseo (Italy) in relation to climate and anthropogenic pressure. We related subfossil Cladocera species composition and density in an 80-cm sediment core collected in the pelagic zone of Lake Iseo to long-term temperature trends and phosphorus concentration inferred by diatoms frustules. The Cladocera remains detected in Lake Iseo sediment reflected the species composition and density of modern pelagic Cladocera assemblages. Cladocera rapidly respond to environmental change, and that climate change combined with eutrophication can induce changes in community composition and species density. At the beginning of twentieth century, when global warming was not yet so accentuated, the nutrient increase in water resulted as the principal driver in determining the long-term development of plankton communities and pelagic food web structure. Moreover, catchment-related processes may decisively affect both species composition and density of the lake planktonic communities due to the decrease of lake water transparency induced by input of inorganic material from the catchment area to the lake. The paleolimnological investigation, through the combined study of biotic and abiotic factor, allowed clarifying the synergic effects of the most important drivers of change in lake ecosystems, suggesting that climatic factors should be considered with nutrient availability as determinant element in controlling the temporal development of plankton communities and pelagic food web structure.

     

Diversity of extremophilic bacteria in the sediment of high-altitude lakes located in the mountain desert of Ojos del Salado volcano,Dry-Andes

Ojos del Salado, the highest volcano on Earth is surrounded by a special mountain desert with extreme aridity, great daily temperature range, intense solar radiation, and permafrost from 5000 meters above sea level. Several saline lakes and permafrost derived high-altitude lakes can be found in this area, often surrounded by fumaroles and hot springs. The aim of this study was to gain information about the bacterial communities inhabiting the sediment of high-altitude lakes of the Ojos del Salado region located between 3770 and 6500 m. Altogether 11 sediment samples from 4 different altitudes were examined with 16S rRNA gene based denaturing gradient gel electrophoresis and clone libraries. Members of 17 phyla or candidate divisions were detected with the dominance of Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes. The bacterial community composition was determined mainly by the altitude of the sampling sites; nevertheless, the extreme aridity and the active volcanism had a strong influence on it. Most of the sequences showed the highest relation to bacterial species or uncultured clones from similar extreme environments.     

Factors determining the spatial structure of benthic communities of a shallow bay

The species composition and the spatial structure of benthos were studied along a transect running at a depth of 1–18 m on the soft bottom substrates of Zapadnaya Bight of Furugelm Island (Peter the Great Bay, Sea of Japan). This area has been proposed as a major site for long-term monitoring of the Far Eastern State Marine Reserve. Hydrobiological samples of different sizes (16 cm², 0.025, and 1 m²) were taken by a diving method at 5-m intervals from the shore. Benthic communities were distinguished using principal component analysis (PCA), Sørensen's similarity indices, and similarity dendrograms. The grain size composition of bottom sediment was determined. Three benthic communities at depths of 1–3, 4–8, and 14–18 m and two transitional zones were distinguished in Zapadnaya Bight. The benthic communities are characterized by a relative constancy of species composition within their boundaries, and by stable ratios of quantitative characteristics of other species from different ecological groups. The transitional zones, which are comparable in extension with the communities themselves, are characterized by changes in species composition and the presence of characteristic species; here, the substrate type changes and sediment grain sorting is decreased.     

Environmental filtering governs consistent vertical zonation in sedimentary microbial communities across disconnected mountain lakes

Subsurface microorganisms make up the majority of Earth's microbial biomass, but ecological processes governing surface communities may not explain community patterns at depth because of burial. Depth constrains dispersal and energy availability, and when combined with geographic isolation across landscapes, may influence community assembly. We sequenced the 16S rRNA gene of bacteria and archaea from 48 sediment cores across 36 lakes in four disconnected mountain ranges in Wyoming, USA and used null models to infer assembly processes across depth, spatial isolation, and varying environments. Although we expected strong dispersal limitations across these isolated settings, community composition was primarily shaped by environmental selection. Communities consistently shifted from domination by organisms that degrade organic matter at the surface to methanogenic, low-energy adapted taxa in deeper zones. Stochastic processes—like dispersal limitation—contributed to differences among lakes, but because these effects weakened with depth, selection processes ultimately governed subsurface microbial biogeography.     

Vertical distribution of bacterial community structure in the sediments of two eutrophic lakes revealed by denaturing gradient gel electrophoresis (DGGE) and multivariate analysis techniques

Vertical distribution of bacterial community structure was investigated in the sediments of two eutrophic lakes of China, Lake Taihu and Lake Xuanwu. Profiles of bacterial communities were generated using a molecular fingerprinting technique, denaturing gradient gel electrophoresis (DGGE) followed by DNA sequence analysis, and the results were interpreted with multivariate statistical analysis. To assess changes in the genetic diversity of bacterial communities with changing depth, DGGE banding patterns were analysed by cluster analysis. Distinct clusters were recognized in different sampling stations of Lake Taihu. Canonical correspondence analysis (CCA) was carried out to infer the relationship between environmental variables and bacterial community structure. DGGE samples collected at the same sampling site clustered together in both lakes. Total phosphorus, organic matter and pH were considered to be the key factors driving the changes in bacterial community composition.     

Homogenization of fish assemblages in different lake depth strata at local and regional scales

相似文献