Limnologica最新文献

The structure and diversity of prokaryotic assemblages in inland waters are strongly related to their habitat. Yet, there is a lack of integrative studies surveying them in different compartments in tropical lakes. This study estimated the diversity and composition of prokaryotic assemblages in sediments, microbialites, and water column in the tropical warm monomictic Lake Alchichica and identified the most representative phylotypes while thermally stratified. The 16S rRNA gene survey showed a distinctive prokaryotic assemblage for each compartment, with 60–78 % of the phylotypes being unique to each one. Sediments accounted for the major prokaryotic diversity in the lake, with chemoorganotrophic bacteria and sulphate reducers as major biogeochemical components. Microbialites showed a high abundance of oxygenic and anoxygenic phototrophs, as well as organotrophs. The prokaryoplancton in the water column was mainly composed of picocyanobacteria and Flavobacteria in the epilimnion, shifting to a high diversity of anaerobic microorganisms in the hypolimnion. These water column assemblages were significantly correlated to pH, ORP, DO, and nutrient concentration. This study shows an integral view of the prokaryotic assemblages in a deep tropical lake related to physicochemical characteristics, from their diversity to their biogeochemical implications, suggesting the role of lake sediments as a possible microbial seed bank.

Siltation has been aggravated by climate changes due more frequent and intense rain events, resulting in greater amounts of sediment in water bodies. These changes have impacted drastically submerged macrophytes growth by light limitations. Despite biological invasions are among the major threats to freshwater biodiversity and invasive submerged aquatic plants also has been impacted by these changes. The main aim of this study was to investigate through an experimental study as two globally invasive freshwater macrophytes, Hydrilla verticillata and Egeria densa, respond to the changes in water transparency caused by siltation. We performed a factorial experiment to test the effect of turbidity increase caused by siltation on growth of these two species. For this, we included sand or mud sediment in containers to obtain without and with siltation treatments. Then both species were planted at the two treatments and grown for 30 days. The main results of our study were that there was a shift in the dominance at the performance of some biological traits between the species, where H. verticillata showed better development of these biological traits than E. densa at treatment with siltation, and the reverse was also true, where E. densa had better performance in without siltation treatment. In summary, our results demonstrated that if the increase in water siltation continues at the current rate, a greater performance of H. verticillata can also be expected and, consequently, the impacts on aquatic biodiversity will also increased. These results may be helpful in predicting the effects of siltation on the development of two globally invasive freshwater submerged macrophytes. Moreover, could increase the ability of managers environmental to predict the future development of ecosystems in relation to invasions by non-native species.

Four populations of freshwater pearl mussel Margaritifera margaritifera were studied at lower sections of three river basins of the eastern part of the Onega Peninsula, Northern European Russia: the Bol’shaya Syarta, the Ust’-Yaren’ga and the Lopshen’ga (including Kamenny Stream). One of the populations from the Lopshen’ga River was discovered for the first time. Here we present preliminary data on the population status of M. margaritifera, its host fishes and glochidia infestation in the studied river basins. Living juvenile mussels and fishes infested by glochidia were recorded only in two waterbodies, i.e., the Bol’shaya Syarta and Ust’-Yaren’ga rivers. The pearl mussel population from the Bol’shaya Syarta River seems to represent the most prosperous among studied ones. The average density of visible mussels was small in the lower section of the river, but the proportion of young mussels was rather high (33.1 %) and intensity of glochidia infection reached 865 glochidia per fish. The highest average density was recorded in the pearl mussel population from the Kamenny Stream, Lopshen’ga River basin. However, only one juvenile mussel and none of host fishes infested by glochidia were recorded in this watercourse that may indicate the population aging and decrease of reproduction. Morphological analyses revealed significant differences between four studied populations of M. margaritifera towards the shell convexity index (SCI) and shell elongation index (SEI). In all studied basins, salmonid fishes were also infested by other parasites, mainly flatworms and their cysts. This factor may negatively impact the salmonid host fish populations that require monitoring of the current situation. The data obtained and future studies will allow to develop a system for protecting and monitoring of populations of a rare species such as the freshwater pearl mussel M. margaritifera.

Understanding biota distribution patterns is essential for ecosystem conservation and restoration. In addition to biogeography, the distribution patterns of aquatic organisms that inhabit rivers vary longitudinally along river networks. Although longitudinal changes in distribution patterns in aquatic organisms along river networks have been studied in single river basins, it is crucial to understand these patterns at a regional ecological scale for broad-scale ecosystem conservation. This study aimed to elucidate the longitudinal distribution patterns of fish fauna and their correlation with environmental factors in several watersheds within the East Setouchi Ecological Region, renowned for its rich freshwater fish diversity in the Japanese archipelago. Data were obtained for 118 species across 10 watersheds and 85 sites, and the surveyed sites were classified into four longitudinal groups based on the similarity of the fish fauna. The lowest group comprised river estuaries, abundant in brackish-water fish, comprising primarily Gobiidae species. In lower watershed areas with low agricultural land and forest cover but high urbanization, all fish species selected as indicators were non-native. Upstream areas with a high percentage of agricultural land featured a mix of native Cyprinidae and non-native species such as Micropterus salmoides and Rhodeus ocellatus ocellatus. The most upstream groups, marked by significantly greater elevations and bed slopes, exclusively comprised native species as indicator species. Analyzing the longitudinal distribution patterns of fish fauna at multiple sites within the same ecological region enabled us to choose endemic fish species as indicators and identify important species for conservation. Additionally, the selection of sites characterized by significant urbanization and strong anthropogenic influences, along with the selection of non-native species as indicators, underscores the urgency of conserving native organisms in these areas, calling for continuous monitoring.

When assessing microplastics (MPs) in freshwater ecosystems, previous studies have primarily focused on natural rivers and lakes, with limited attention to urban water source areas. Sediments, recording the steady process of MPs accumulation during a long period of time, can act as an important sink for MPs. In this study, we investigated the distribution, characteristics and pollution evaluation of MP contaminants in sediments of a water supply reservoir of Hefei City (the Dafangying Reservoir). Meanwhile, the differences of MP concentrations in sediments in rural and urban areas were also compared. Our results detected five shapes, seven colors and six polymer types of MPs in sediments of the Dafangying Reservoir. Polystyrene, polyethylene and polypropylene were the most abundance types of MPs identified. The average MPs abundance of sediments in rural areas was 83.20 ± 32.99 n/100 g dry weight (d.w.), and 182.67 ± 72.21 n/100 g (d.w.) in urban areas. The total MP concentrations were significantly higher in sediments of urban sites than that in rural sites, which can be ascribed to more complex and diverse MP sources triggered by intensive anthropogenic activity in cities. Specifically, we also demonstrated significantly higher microbead abundance in urban sites, which may result from the widespread use of microbead in personal care products. Given the complexity and diversity of MPs in urban areas, we exhibited a relatively higher abundance of MPs in the Dafangying Reservoir than that in other rural larger reservoirs. According to the index of geoaccumulation, the sedimentary MPs were assessed as moderately polluted. Our study enriches valuable data on the distribution of MPs contaminants in water supply reservoir, and provides theoretical references for MPs control and management in reservoir ecosystems.

Elevated geosmin concentrations in drinking water reservoirs can lead to customer complaints and increased treatment costs for utilities. Use of molecular approaches, like qPCR and targeted amplicon sequencing, can help with prediction and preventive measures, but many of the primers targeting the geosmin synthase gene suffer from limited coverage of taxa or poor specificity. Here, a set of primers (CGeo1F/R) were developed that had high specificity for geosmin synthase in cyanobacteria without the use of probes. When tested on samples from three drinking water reservoirs with elevated geosmin levels, these primers amplified the geosmin synthase gene in seven cyanobacterial genera, including Dolichospermum, Aphanizomenon, Cylindrospermum, Planktothrix, Nostoc, Coelosphaerium, and Tychonema. These primers exhibited acceptable amplification efficiency (∼ 90 %) and a linear amplification range of 6 × 10¹–6 × 10⁵ copies per ml in lake water. Within the limited set of samples used to evaluate these primers, a good correlation was observed (r = 0.8) between abundance of geosmin synthase and geosmin concentration. When compared to some existing, well-utilized primers in the literature, these new primers had better specificity and amplification properties, and thus may prove valuable to other researchers.

Environmental, spatial, and temporal factors play an important role in beta diversity in metacommunities. Most studies are based only on species identity, and little is known about how these factors affect multiple facets of diversity. Here, we assessed the effect of local (chemical, physical, and hydrological), spatial, and temporal variables on taxonomic, functional, and phylogenetic beta diversity in a zooplankton metacommunity in two urban rivers. The partition of the beta diversity into its components - replacement and abundance difference - was performed using the Bray-Curtis index. Distance-based redundancy analysis and variation partitioning were used to assess the importance of predictors for the beta diversity. We found that beta diversity was high and mostly influenced by environmental factors and, to a lesser extent, by spatial and temporal factors in all facets. The abundance difference was the dominant component of beta diversity in all facets and was mainly explained by the environment and space, while replacement had a low explanation, in general, and was more related to temporal factors. These results reflect anthropic pressures in these environments and suggest that a multifaceted approach to beta diversity provides complementary information about the processes structuring the metacommunity and about conservation strategies of these impacted environments.

The quality and quantity of Mongolia’s water resources are being degraded by ineffective water-management. There is no widely accepted biomonitoring system for Mongolia, only hydrological and chemical monitoring, with limited relevance for living organisms. Therefore, this study has aimed to develop a Mongolian-specific multimetric index and biocriteria applicable to the biological assessment of Mongolian streams. A total of 66 stream sites in northern Mongolia were selected representing different gradients of land use. In total, 30 candidate metrics representing the following four categories of ecological condition were used: diversity/richness, composition/abundance, trophic status, and tolerance/sensitivity. The resulting candidate metrics were evaluated using a stepwise procedure for metric variability, redundancy, sensitivity, and responsiveness to environmental gradients. According to the Mann-Whitney U test, 21 metrics showed statistically significant differences between the reference and impaired groups (P < 0.05). A metric showed interquartile overlap and thirteen metrics were redundant based on Spearman’s correlation analysis (r > 0.8). Finally, five metrics were retained and included in the multimetric index system and all clearly distinguished reference and impaired sites. Then the range of the multimetric index score (numerical value 0–1) was subdivided into five categories (reference/excellent ≥ 0.8, good < 0.8 to ≥ 0.6, moderate < 0.6 to ≥ 0.4, poor < 0.4 to ≥ 0.2, severe < 0.2) related to level of impairment. Thus, this multimetric index successfully distinguished reference from impaired conditions, demonstrating its applicability for northern Mongolian stream assessment. Hence, the Mongolian-specific Macroinvertebrate Multimetric Index (MMI-MON) can be used as a principal assessment tool for assessing waterways in northern Mongolia and possibly throughout the country, detecting future changes and providing valuable information for land-use management and conservation of aquatic ecosystems of Mongolia.

Global warming has changed climate patterns worldwide causing an increase of extreme weather conditions that have altered annual seasonal hydrological regimes. These extreme climate-driven shifts modify habitat availability and can influence freshwater communities in disruptive ways. Our study investigates how changes in annual seasonal hydrological regimes affect the community structure and the Functional Feeding Groups (FFG) of benthic macroinvertebrates in two Brazilian biodiversity hotspots, the Brazilian Tropical Savannas (a.k.a., Cerrado) and Atlantic Forest biomes. We investigate whether annual variation in precipitation between biomes influence composition, richness, and abundance of benthic macroinvertebrates and their proportions of FFG. We demonstrate that differences in annual precipitation rates affect the composition and abundance, but not richness of benthic macroinvertebrates. Changes in community structure are related to changes in annual precipitation, which modify stream variables. Our findings suggest that annual seasonal changes in hydrological precipitation modify benthic macroinvertebrate communities, especially in Cerrado, where dry seasons are more pronounced. Therefore, annual changes in precipitation rates may disrupt the benthic macroinvertebrate communities in tropical savannas, potentially leading to biodiversity loss.

Habitat diversity plays a crucial role in shaping the structure and distribution of benthic macroinvertebrate communities. However, few studies have investigated the concurrent effects of such drivers operating at different spatial scales in mountain streams. Here, we assessed which environmental factors at different spatial scales, related to stream/river type and substrate, influence the diversity of benthic macroinvertebrate assemblages in mountain streams and rivers. Within the framework of the aquatic investigations of the Biodiversity Monitoring South Tyrol (BMS) – a newly-established, regional-based, long-term biodiversity monitoring program – benthic macroinvertebrates and a set of environmental factors describing water quality, stream/river hydromorphology and in-stream habitat characteristics were collected and analysed. The variation in total density, taxonomic richness, Shannon evenness and % Ephemeroptera–Plecoptera–Trichoptera taxa of stream benthic macroinvertebrates was assessed at multi-scale habitat levels, in 48 sampling sites across the mountainous region of the Autonomous Province of Bolzano/Bozen (Italy). The effects of stream/river type, substrates and different environmental factors on community composition of benthic macroinvertebrates were quantified, using a stepfoward Redundancy Analysis (RDA) and generalized additive models (GAMs). In addition, we performed an Indicator Value analysis to detect taxa that were significantly associated with a specific substrate and/or stream/river type. Overall, we observed significant differences in benthic biological metrics among both stream/river and substrate types. We also found at least one indicator taxa for each stream/river type, with environmental factors acting at reach and large-spatial scale – temperature, stream channel stability, elevation – being the key drivers in shaping macroinvertebrate distribution patterns in the analysed mountain rivers. While significant differences in macroinvertebrate community structures were found among substrates, the influence of stream/river type conditions was particularly evident. Apart from ranking environmental variables worth including in a long-term aquatic biodiversity monitoring program in mountain areas, our study provides a baseline for practical applications. For instance, depending on the desired outcome of habitat heterogeneity restoration, it can suggest the optimal scale (landscape vs. reach vs. patch) for prioritizing in-field interventions.