Rotifer Community Research Articles

Diversity of Rotifera in Freshwaters of Bolivia: An Updated Checklist

Biodiversity records are of great importance, especially in light of the biodiversity crisis. Here, we present a study on the diversity of rotifers in Bolivia based on an extensive investigation of the literature published so far. Through this approach and an analysis of samples from 207 water bodies of the country, we updated the checklist of reported species. This study revealed a total of 195 species of rotifers previously reported; we identified 153 species in our samples, with 84 of them being reported for the first time in Bolivia. Thus, a total of 279 species are known at present in this country. Our findings suggest that Bolivia has a rich and diverse rotifer community, with many species likely to be unique to the region.

Evidence of Climate Change and the Conservation Needed to Halt the Further Deterioration of Small Glacial Lakes

Although somewhat debated, it is generally agreed in Europe that small water bodies comprise lentic ecosystems that are shallow (less than 20 m) and have a surface area of a few hectares (less than 10 ha). In Albania, 84 glacial lakes constitute a substantial portion of the aquatic ecosystems that sustain high levels of biodiversity, metabolic rates, and functionality. This paper discusses the integration of ecological sustainability into ecosystem services (i.e., cultural, regulatory, and sustaining services) and the national ecological networks of protected sites. This integration is particularly important in light of recent advancements regarding European integration. It is also important due to the catchment continuum, which addresses biodiversity values and gradients that, in this work, are considered using rotifer communities and aquatic plant species. The main causes of the stressors on small ecosystems are inappropriate land use, water pollution, altered habitats, non-native species introduction, resource mismanagement in basins, inadequate planning, and a lack of sector integration. The glacial lakes reflect climate change elements through: an increased number of dried glacial lakes, so only 84 remain functioning; the water level is slowly being reduced; the oscillation of the water level is steadily increasing; and the eutrophication process is rapidly advancing.

Rotifer functionality as a potentially useful indicator of lake browning

Lake browning is considered a severe water quality problem in lake ecosystems, but it has received considerably less attention in water protection than eutrophication. Current metrics used in lake surveillance monitoring programmes, including the European Union’s Water Framework Directive, do not reflect browning sufficiently. The aims of the study were to explore the potential role of the functionality of rotifers as browning indicators and to improve understanding of the environmental parameters driving the functionality and diversity of rotifers. Seasonal data on rotifer communities and water quality from seven lakes with differing water colour and trophic conditions were analysed. The feeding guilds of rotifers enabled differentiation between lakes in terms of their ecological conditions, and, in particular, eutrophic and brown-water lakes were clearly distinguished from other lakes. The guild ratio of rotifers was positively affected by water colour, but inversely related to total phosphorus concentration. Our results suggest that zooplankton functionality provides a potential tool to assess ecosystem dynamics, particularly when assessing lake browning. Thus, our results suggest that application of the guild ratio of rotifers is a promising method to estimate the general browning status of lakes and may complement the metrics used in Water Framework Directive.

Investigating the Plankton Diversity and Physicochemical Properties in a Temple Pond in Tamil Nadu, India: Taxonomic Composition, Seasonal Variations, and Ecological Implications

The present study explores the dynamics of phytoplankton and zooplankton in the Swetharanyeswarar temple pond located in the Mayiladuthurai district of Tamil Nadu, India. The study investigates species composition, diversity, and seasonal variations of these microscopic organisms, considering the ecological implications for the local food chain. Phytoplankton (Seven species), dominated by diatoms, cyanobacteria, and various other taxa, plays a fundamental role as primary producers, influencing nutrient cycling and climate patterns. The presence of Microcystis sp., associated with harmful algal blooms, emphasizes the need for monitoring and understanding its ecological implications. Zooplankton (13 species), including Rotifera, Copepods, and Calanoids, showcases a diverse community with distinct taxonomic members. The Rotifer community peaks in January, gradually declining, while Copepods exhibit notable diversity in April. Calanoids, represented by Macrocyclops albidus and Macrocyclops fuscus, display temporal fluctuations in diversity indices, indicating potential ecological changes influenced by environmental factors. The population of each zooplankton group is expressed as an average number of individuals per liter. Water quality parameters, crucial for understanding ecological dynamics, were meticulously measured in triplicates. Statistical analyses were conducted using Microsoft Excel to process and present the data as percentages.
 The study establishes a connection between zooplankton dynamics and physicochemical parameters, highlighting correlations with turbidity, pH, and organic pollution indicators, as per the methods of APHA. Monthly variations in zooplankton populations reveal dynamic ecological patterns influenced by temperature and organic matter. The species richness index reflects a well-balanced distribution within the planktonic community, suggesting a healthy and resilient ecosystem in the Swetharanyeswarar temple pond. Statistical analysis involves expressing the zooplankton population as an average number of individuals per liter and presenting water quality parameters as percentages using Microsoft Excel. These findings underscore the importance of continued monitoring to decipher long-term trends and implement targeted strategies for maintaining water quality and ecosystem health. Overall, this research contributes valuable insights into the intricate relationships between phytoplankton, zooplankton, and environmental factors in a freshwater ecosystem, providing a foundation for informed fisheries management strategies and conservation efforts.

Spring and autumn rotifer community structure differentiates shallow water bodies in two European ecoregions: Poland and Croatia

Rotifer structure may serve as predictor of environmental features, including temperate subclimates between water bodies. The difference in latitude between two temperate regions (Poland vs. Croatia) affects the identification of particular environmental factors that subsequently influence the taxon-related indices of rotifers. A study on 10 water bodies found that taxon-trait indices were sensitive in identifying latitude differences, even though extreme weather conditions were not considered, and only two seasons (spring and autumn) were examined. A variable rotifer community, with a high share of rare species, was obtained. We found a distinctiveness of abiotic factors between both countries, indicating a higher trophic state in Poland. Although habitat conditions were more similar in spring compared to the autumn, the percentage of rotifer common taxa was alike in both seasons but variation in distinct species community was clear. Trophic state increase in Poland was reflected in the structure of dominant and distinct species, with a wide range of eutrophy indicators. Comparing how rotifer species respond to environmental conditions is important for developing methods to assess trophic state changes due to climate change. Single species, distinct or rare species, are often the first sign of changes.

Evaluation of trophic state conditions in the three urban perennial lakes of the Coimbatore district, Tamil Nadu: Based on water quality parameters and rotifer composition

This study aims to examine the trophic state conditions in the three major urban perennial lakes of the Coimbatore district based on the physicochemical properties and rotifer community structure. The study was conducted for a period of three months, from January 2023 to March 2023. The water and plankton samples were collected twice a month. The measured physicochemical properties showed that pH, salinity, total hardness, nitrate, and phosphate were found to be higher in Kumarasamy lake, followed by Ukkadam and Valankulam lake ecosystems. The higher rotifer population density was observed in Valankulam lake (1820 Ind./L), and lower in Kumarasamy lake (1080 Ind./L). In this study, Brachionidae species were abundantly found in the three perennial lake water environments, followed by Asplanchnidae, Lecanidae, Trichocercidae, and Filiniidae. In addition, a total of 28 freshwater rotifer species were reported for the first time from the three perennial lakes of the Coimbatore district, respectively. The determined trophic state index (TSI) (47.57) and rotifer trophic state index (TSIROT) (51.25) values affirm that the three perennial lakes are under meso-eutrophic conditions. The examined diversity indices values revealed that species dominance (D) and species richness (SR) are higher in Valankulam lake, followed by Ukkadam and Kumaraswamy lake ecosystems. This difference may be due to the influence of human activities and the mixing of various points and non-point sources of pollutants. The present study concluded that the three perennial lakes were moderately polluted by various sources of pollutants; therefore, continuous monitoring is needed for the conservation of flora and fauna diversity in the three perennial lakes of the Coimbatore district.

Combined effects of microplastics and temperature on the competition between Brachionus havanaensis and Brachionus calyciflorus (Rotifera)

Aquatic organisms are constantly exposed to effluents which often contain microplastics. Microplastics adversely affect aquatic organisms as a result of mechanical damage during ingestion or intoxication by chemicals adsorbed on the microplastics. Sub-optimal temperatures may acerbate the adverse effects of microplastics on aquatic biota. Brachionid rotifers, such as Brachionus havanaensis and Brachionus calyciflorus, are common in tropical freshwaters. They are generalist filter feeders capable of consuming microplastic particles of a wide size range 0.05 to 40 µm, which can eventually affect growth and competitive interactions among species. Here, we evaluated the effect of 30 µm beads of polystyrene microplastics at 10 and 20 mg l−1 on the population growth and competition of B. havanaensis and B. calyciflorus at 20 and 25 °C using 0.5 × 106 cells ml−1Chlorella vulgaris as food. Population growth decreased in treatments with microplastics at both temperatures as compared to the controls. The population growth rates ranged between 0.21 and 0.38 d−1 for B. calyciflorus, and between 0.27 and 0.48 d−1 for B. havanaensis. The presence of the competing species significantly lowered the population growth rate for B. calyciflorus but not for B. havanaensis. On the other hand, while the presence of the microplastics had little impact on the population growth rate of B. calyciflorus in the presence of the competitor, the reverse was true for B. havanaensis, especially at 20 °C. Our results show that the presence of microplastics may affect rotifer community structure in natural water bodies.

The influence of locks on zooplankton in canals (the Bydgoszcz Canal and the Noteć Canal, Poland)

Artificial waterways are characterized by dams and locks that slow water flow. Such conditions can influence the environment of freshwater organisms, including the zooplankton community. Our research aimed to assess the impact of environmental and hydrological conditions on the zooplankton of sites upstream and downstream of canal locks. The study was carried out in 2021 and 2022. Water samples were collected monthly from two canals during the growing season. We evaluated how water flow velocity and selected environmental parameters (i.e., water temperature, Secchi disk visibility, conductivity, oxygen concentration, saturation, pH and chl-a concentrations) influence the zooplankton diversity (T) density (N) and biomass (B). Our study showed that the zooplankton of the canals was highly diverse. Rotifers dominated over crustaceans in diversity and density at all sites of canals. The statistical analysis revealed differences in environmental and biological conditions between habitats located upstream and downstream of locks. Rotifers density and biomass changed approximately proportionally to changes in chlorophyll at sites upstream of locks. It supports the hypothesis that rotifer communities are defined by the bottom-up effect linked to food supply (phytoplankton). The growth of crustaceans (density and biomass), as well as total zooplankton biomass, was affected by water temperature at sites downstream of the lock.

Homogenization of Functional Diversity of Rotifer Communities in Relation to Eutrophication in an Urban River of North China.

Rapid urbanization has triggered nutrient loading, which will inevitably lead to the eutrophication of water bodies and further affect the structure of aquatic populations. At present, eutrophication is a significant challenge for urban aquatic ecosystems. However, we still know little about the correlation between eutrophication in urban rivers and the composition of aquatic functional groups. The effects of urban river eutrophication on rotifer communities were investigated using an annual field survey of the Jinan section of the Xiaoqing River, a typical urban river in northern China. Using functional diversity (FD) and beta diversity, the spatiotemporal variation of the aquatic biological functional groups regime along stretches subject to different eutrophication was investigated. The functional evenness (FEve) and functional divergence (FDiv) decreased significantly with the increment of the trophic level index. Functional diversity exhibits an extremely low level across functional groups, with the richness difference (RichDiff) being an important component. The results indicate that eutrophication led to the homogenization of rotifer communities. This can be attributed to the functional homogenization of the rotifer community in the Jinan section of the Xiaoqing River. The observed homogenization may be due to widely distributed species complementing the ecological niche space. Our findings provide valuable information on the conservation of the urban river under the threat of eutrophication caused by high-intensity human activities.

Functional diversity and redundancy of rotifer communities affected synergistically by top-down and bottom-up effects in tropical urban reservoirs

Rotifers are one of the most important functional groups in lentic freshwaters, and mainly structured by predation or competition from crustaceans and food availability from phytoplankton. Their functional traits involving in defense and food utilization provides insights into the functional diversity and assembly of their communities. Tropical urban reservoirs are commonly subjected to intense fish culture and strong eutrophication, and rotifers become the dominant component of the zooplankton communities and play an important role in ecosystem functioning. Knowledge about the functional diversity and functional redundancy of rotifers is therefore of relevance for effective ecosystem management. In tropical reservoirs, we hypothesized that functional diversity and redundancy of rotifer communities are synergistically affected by top-down and bottom-up effects, and that they strongly change seasonally with environmental conditions at local scale as well as with connectivity between reservoirs at regional scale. To test these hypotheses, we investigated the seasonal dynamics of taxonomic and functional diversities in twenty-five tropical urban reservoirs. Traits of rotifers mainly associated with body size, feeding behavior, and defensive strategies were used to explore the drivers of functional diversity and functional redundancy. We found that, at the local scale, both taxonomic alpha and functional alpha diversities of rotifers increased from the wet to the dry season, whereas the functional alpha redundancy showed no significant change. Crustacean abundance (top-down effect) and phytoplankton biomass (bottom-up effect) were the dominant variables explaining the variation of taxonomic and functional alpha diversities. At the regional scale, both the taxonomic and the functional beta diversities of rotifer communities decreased from the wet to the dry season. However, functional beta redundancy increased, accompanied by a reduction in environmental distance, i.e., biological and physicochemical distance. Thus, weakened environmental heterogeneity and strengthened homogenization of biological selection resulted in a more similar functional trait composition than a more similar taxonomic composition between reservoirs.

Temporal and spatial dynamics of rotifer communities in the Pearl River Delta (China) with emphasis on DNA metabarcoding versus morphology to assess rotifer diversity

Temporal and spatial dynamics of rotifer communities in the Pearl River Delta (China) with emphasis on DNA metabarcoding versus morphology to assess rotifer diversity

Benefits of combined environmental DNA and microscopy for diversity monitoring in rotifer community: A mesocosm experiment

Rotifers are crucial for the monitoring of aquatic ecosystems because of the sensitive response of rotifer community structure to environmental changes. Comparisons and combinations of meta-barcoding (sequence analysis) and traditional morphological identification for rotifer community responses are rare. To better understand the differences between the two approaches, we conducted a study using 48 mesocosms (2500 L) and a combination of warming, nutrient loading, and pesticide to evaluate the applicability of both methods to rotifer communities in order to better understand how rotifer communities respond to multiple environmental stressors. The findings demonstrated that the degree of matching between both techniques was limited, despite the fact that there was a substantial positive association between the morphology abundance determined by morphological identification and the sequence abundances determined by eDNA metabarcoding. Although the two methods had similar responses to various environmental stresses, sequence analysis can identify rotifers that are difficult to identify with traditional methods such as Bdelloidea, while classical morphological methods were more suitable for assessing the effects of various environmental changes on rotifer communities. This study provided valuable implications for monitoring and managing aquatic ecosystems since it enables us to spot changes in the rotifer community structure early on and take the necessary precautions to safeguard these sensitive ecosystems.

Appearance of the rotifer community as a potential indicator of stable paleohydrological conditions in peatlands since the Late Glacial: a case study of three wetlands in Poland

In paleolimnological studies, rotifers are usually a very rare component in multiproxy research. These small invertebrates are identified from sediments by their loricas. Analysis of subfossil rotifers was conducted for sediment cores collected from three peatlands in within Poland: the Grel raised bog (S Poland, Carpathians, Orawa-Nowy Targ Basin), the Imszar raised bog (NE Poland, Podlasie Region), and the Podemszczyzna peatland (SE Poland, Sandomierz Basin). Results were compared with multiproxy analyses of peat deposits: pollen of aquatic and mire plants, non-pollen palynomorphs (NPPs), and geochemical analyses. Analysis of the rotifers indicated the occurrence of the bdelloid species Habrotrocha angusticollis (Murray, 1905). In all profiles of the studied peatlands, the occurrence of rotifers was not correlated with pollen of aquatic or mire plants or NPPs; they seem to be more related to geochemical indices. The highest densities of rotifers were found in profile sections without significant fluctuations of geochemical variables, i.e. those with higher Na/K (chemical denudation) ratios and stable redox conditions (Fe/Mn ratio). The study of subfossil rotifers supported by multiproxy analysis of peat deposits could be a useful tool for indication of periods with stable palaeohydrological conditions during the Late Glacial and Holocene.

Application of calcium peroxide for efficient treatment of surface water turbidity: Mechanisms and microbial community responses

In this study, calcium peroxide (CaO2) was added to two types of water to remove turbidity. The effects of CaO2 on water quality, Ca content and microbial communities were also examined. The results showed that CaO2 significantly improved the transparency of highly turbid water induced by algae. Compared with the control group, 5, 10, and 20 mg/L CaO2 reduced the turbidity by 56.80%, 81.66%, and 82.54%, respectively. Considering the actual effect and cost, 10 mg/L CaO2 was the recommended dosage. Furthermore, the addition of CaO2 increased the degree of humification in the water and Ca content in the sediment. However, the addition of CaO2 did not significantly increase the concentration of Ca2+ in the water. Additionally, CaO2 first decreased the richness and diversity of the bacterial and fungal communities. However, this effect gradually disappeared over time. The abundance of cyanobacteria decreased to 0 after 168 h. Actinobacteria and Compilobacteria were also inhibited by CaO2. At the genus level, Flavobacterium, Sphingomonas, Pseudomonas, and Limnohabitans, which occupied key nodes, were tolerant to CaO2, and CaO2 had only a minor impact on the microbial ecological networks. Moreover, the eukaryotic rotifer community was destroyed. CaO2 increased the abundance of chemotrophic heterotrophic functional groups but decreased that of the functional groups. These findings provide guidance for the use of CaO2 to improve water turbidity and water ecological restoration.

Discordant spatiotemporal dynamics of functional and phylogenetic diversity of rotiferan communities exposed to aquaculture effluent.

The growth of the human population brought about the global intensification of aquacultural production, and aquaculture became the fastest growing animal husbandry sector. Effluent from aquaculture is an anthropogenic environmental burden, containing organic matter, nutrients and suspended solids that affect water quality especially in the water bodies of high biodiversity and conservation value. Water quality assessment often relies on bioindicators, analysing changes in taxonomic diversity of various freshwater organismal groups. Stepping beyond taxon diversity, we used functional and phylogenetic diversities of rotifers to identify factors affecting their community organization in response to an aquaculture effluent gradient in the largest oxbow lake in the Carpathian Basin, Hungary. Sampling was carried out three times per season at five points along a 3.5 km section of the oxbow lake, including the point of effluent inflow. We used eight traits to evaluate functional diversity: body size, trophi type, feeding mode, protection type, body wall type, corona type, habitat preference and tolerance level. Functional and phylogenetic distances among the 24 species identified indicated trait conservatism. Rotiferan diversity increased with increasing distance from the point of influx in spring and summer. Among the factors affecting community organization in spring and summer, we find examples of environmental filtering, while in autumn the role of biotic interaction is more frequent. Under nutrient-rich conditions in spring and summer, organisms belonging to the same functional group were dominant, whereas under oligotrophic conditions, more diverse but less abundant groups were present. Considering functional and phylogenetic traits allowed us to identify organising forces of rotifer communities in the largest oxbow lake of the Hungarian Lowland.

Rotifer distribution patterns in relation to dissolved organic matter in the middle reaches of Huai River Basin during the dry season.

Increased dissolved organic matter (DOM) may induce water browning and affect zooplankton communities by changing photochemical environment, microbial food web, and bioavailability of organic carbon supply. However, little is known about the relationship between DOM components and rotifers in natural rivers, relative to the cladocerans and copepods. Here, we investigated the spatial patterns of rotifer distribution in relation to DOM by collecting forty-four water samples from four areas in the middle reaches of Huai River Basin. Results revealed that DOM was described by two humic-like and two protein-like components. There were significant differences in the composition and diversity of rotifer communities among areas, which might be related to autochthonous and allochthonous DOM as well as geographical distances. Specifically, rotifer communities were mainly related to molecular weight, substituents on the aromatic ring, humification level, and protein-like materials. Autochthonous and fresh DOM was positively associated with rotifer abundance and richness, and terrigenous humic-like substances were positively associated with rotifer diversity and evenness. There was a reciprocal effect between rotifer and DOM. Our findings will contribute to the understanding of the possible effects of water browning on rotifer communities, providing new insights into the key role of DOM and rotifer in the energy transfer of aquatic systems.

Rotifers (Rotifera: Monogononta) Associated with Littoral Macrophyte Habitats in Flooded Neotropical Ponds: A Qualitative Study

Rotifers represent an important component of freshwater zooplankton. The high richness of taxa, particularly in littoral macrophyte zones of water bodies in tropical and subtropical flood-prone areas, is a repeatedly reported fact. However, studies on the composition of periphytic rotifers in the Neotropics are reduced and almost non-existent in some regions. A qualitative study on rotifers (Monogononta) associated with littoral aquatic vegetation and their seasonal variation was carried out in three flood-prone ponds in the “Esteros de Camaguán Fauna Reserve” in the Venezuelan plains. For the selection of the collection sites, the two-stage stratified method with proportional affixation was used. Samples of macrophytes and the water associated with them were taken in littoral zones. The percentages of occurrence and numerical frequency were calculated for each rotifer taxa. The faunal similarities and correlations within and between ponds in the same and different climatic seasons were estimated using the Jaccard and Spearman coefficients (α = 0.05), respectively. In total, 102 rotifer taxa associated with 11 species of aquatic macrophytes were identified. The genus Taphrocampa with two taxa plus ten other taxa, are new records for Venezuela and one of them for South America. The taxocenosis and the geographic distribution of the reported taxa reflect a typical composition of the littoral zones of tropical regions. The total richness of both planktonic associated with aquatic vegetation and periphytic assemblages were similar. The highest richness of rotifer taxa coincided with the rainy season and the lowest with the early rainy season. The rotifer fauna presented low similarity values within and between ponds according to seasonality and, with some exceptions, between planktonic and periphytic environments. The importance of sampling periphytic rotifers and the influence of the flood cycle, and the degree of macrophyte development in the structuring of periphytic rotifer communities, were confirmed.

How do rotifer communities respond to floating photovoltaic systems in the subsidence wetlands created by underground coal mining in China?

Along with the increasing demand for energy and pressure to reduce carbon emissions, floating photovoltaic (FPV) systems are increasingly built on the surface of water bodies with the aim to produce clean energy. However, little is known about how FPV systems influence freshwater ecosystems, e.g., their zooplankton communities. We investigated how rotifer communities responded to FPV systems in subsidence wetlands created by underground coal mining in the North China Plain. Diversity metrics of the rotifer communities were compared between wetlands with and without FPV systems. The density of rotifers was higher in wetlands without FPV systems. In contrast, rotifer diversity as represented by Shannon-Weiner and Pielou evenness indices was higher in the FPV-covered wetlands, while there was no difference in species richness between the two types of wetlands. Furthermore, community structures differed between the two types of wetlands, in large part reflecting differences in the relative abundance of five dominant species found in both types of wetlands. These differences in rotifer assemblages were in large part explainable from environmental changes caused by the FPV panels, notably reduced light availability and water temperature, leading to reduced phytoplankton production. These findings show that FPV systems cause major changes to rotifer communities in these subsidence wetlands and likely in wetlands more generally, and monitoring of the longer-term effects is recommended given the fundamental role of zooplankton in freshwater ecosystems.

Multivariate Analysis of Rotifer Community and Environmental Factors Using the Decomposed Components Extracted from a Time Series

Zooplankton abundance patterns exhibit apparent seasonality depending on seasonal variations in water temperature. To analyze the abundance patterns of zooplankton communities, it is necessary to consider the environmental factors that are essential for zooplankton community succession. However, this approach is challenging due to the seasonal variability of environmental factors. In this study, all rotifer species inhabiting a water body were classified into three groups based on their abundance and frequency of occurrence, and decomposition method was used to classify them into groups that exhibit seasonal vs. non-seasonal variability. Multivariate analysis was performed on the seasonal, trend, and random components derived from the classical decomposition method of zooplankton abundance and related environmental factors. This approach provided more precise results and higher explanatory power for the correlations between rotifer communities and environmental factors, which cannot be clarified with a simple abundance-based approach. Using this approach, we analyzed the seasonality-based patterns of the abundance of rotifer species by dividing the environmental factors into those associated with seasonal and non-seasonal variabilities. Overall, the results demonstrated that the explanatory power of redundancy analysis was higher when using the three time series components than when using undecomposed abundance data.

Specific diversity and abundance of communities of microcrustaceans and rotifers in two ponds, Mokolo and Mopa in the city of (Bertoua, Cameroon)

Specific diversity and abundance of communities of microcrustaceans and rotifers in two ponds, Mokolo and Mopa in the city of (Bertoua, Cameroon)