How wide to cast the net? Cross‐taxon congruence of species richness,community similarity and indicator taxa in ponds

1. Broad‐scale assessments of biodiversity often rely on the use of surrogate taxa, whose reliability has rarely been tested, particularly in freshwater systems. Here we use data from 46 ponds in two regions of the U.K. to explore the performance of macroinvertebrate taxa as surrogates for the rapid assessment of pond biodiversity. For the four dominant taxonomic groups in these ponds (Chironomidae, Coleoptera, Gastropoda and Trichoptera) we explore cross‐taxon species richness relationships in each of the two regions, and also determine the degree of concordance between the different taxa in accurately representing the similarity relationships between pond assemblages. 2. Patterns of cross‐taxon congruence in species richness were highly variable among taxa and study sites, making the use of a single taxon as a predictor of overall macroinvertebrate species richness problematic. In contrast, all four taxa show >70% congruence with the pattern of community similarity between sites resulting from the entire macroinvertebrate dataset, this result being consistent within and between regions. Canonical correspondence analysis demonstrated that all taxa were related in a similar manner to measured environmental parameters, meaning that limited additional ecological information is gained by including a wider range of pond taxa in rapid site assessment. 3. Single taxonomic groups can, therefore, perform consistently as indicators of community similarity between ponds, and no one taxon dramatically outperforms any other in this respect. The relative merits of the four focal taxa as surrogates for pond invertebrate assemblage composition are discussed with reference to ease of survey, ease of identification and ecological range occupied. 4. It is suggested that Coleoptera have a number of advantages as a surrogate taxon, being diverse, easily sampled, readily identified, taxonomically stable, ecologically well understood and occurring across a wide spectrum of pond types. They are therefore recommended for use as a focal group in rapid pond biodiversity assessments, employing an approach such as ours, which examines patterns of assemblage similarity, rather than species richness alone.     

A proposal of framework to obtain an integrated biodiversity indicator for agricultural ponds incorporating the simultaneous effects of multiple pressures

One of the promising approaches to monitoring biodiversity is assessing the status of pressures driving the biodiversity state. To achieve this, we need to identify the principal pressures that cause simultaneous biodiversity loss across taxonomic groups and clarify how multiple pressures act synergistically or at least simultaneously to decrease biodiversity in the focal ecosystem. Here, we used a series of 64 ponds as a case study and we developed a framework for an integrated biodiversity indicator that took into consideration the estimated relative importance of multiple pressures. The indicator is defined as a function of the pressure(s) and is parameterized to explain a number of individual indicators of biodiversity, such as richness, abundance, and functional diversity of focal taxa. We selected aquatic macrophytes, Odonata, and benthic macroinvertebrates as the focal taxa. In addition, we focused on three types of pressure: eutrophication (represented by total phosphorus, total nitrogen, suspended solids, chlorophyll a, and density of cyanobacteria of pond water), habitat destruction (land-use type around the pond and pond bank protection), and invasive alien species (abundance of bluegill, largemouth bass, red swamp crayfish, and American bullfrog). We then evaluated the relationships among direct pressures and the individual biodiversity indicators and used a hierarchical Bayesian approach to calculate the integrated biodiversity indicator. Using this framework, we demonstrated that eutrophication had greater effects on the state of biodiversity of the agricultural ponds than did habitat destruction or the presence of invasive alien species. We also showed that the integrated indicator could well explain the behaviors of several individual biodiversity indicators, including total richness, endangered species richness, and functional diversity of focal taxa. These results demonstrate the advantages of the framework in providing a more practical method for assessing biodiversity, and quantifying the relative importance of the major threats to biodiversity to prioritize strategies in conservation planning and policy making.     

Effects of methoprene and Bti (Bacillus thuringiensis var. israelenis) on non-target insects

The effects of mosquito larvicides Bacillus thuringiensis israelensis (Bti) and methoprene, on non-target benthic invertebrates were studied in a divided pond experiment in south-central Minnesota, USA, during the spring and summer of 1989. Density and biomass of insects and other benthic macroinvertebrates were quite low in all sections of the three ponds studied, which may have been due to three consecutive years of drought, but richness appeared to be high and we observed no evidence of dominance by a particular group. We also saw no evidence of negative effects of larvicide treatment on density or biomass of any invertebrate group, nor was there a treatment-related decrease in richness of benthic invertebrate taxa under these drought conditions.     

Biodiversity patterns of nutrient-rich fish ponds and implications for conservation

Nutrient-rich water bodies are usually expected to host low species richness at the local scale (water body). Nevertheless, they can support a diverse and sometimes unique biodiversity when diversity is considered at a regional scale. This discrepancy between the two scales is well documented for natural water bodies, but little is known about biodiversity of artificial water bodies, like fish ponds. We hypothesise that nutrient-rich water bodies can collectively host high species richness at the regional scale. Thus, these are important ecosystems for the regional conservation of biodiversity. We investigated 84 fish ponds in the Dombes region, France, with five taxonomic groups: macrophytes, phytoplankton, macroinvertebrates, dragonflies, and amphibians. Species richness patterns were determined for α- (single pond), β- (between ponds), and γ- (regional pond network) levels. For most studied species groups, richness per fish pond and at the regional level proved to be relatively high in comparison with natural ponds in other landscapes. Contribution of α-diversity to regional diversity was highest for dragonflies with 41 %, and lowest for amphibians and macrophytes with 16 and 18 %, respectively. For macroinvertebrate families and phytoplankton genera it was intermediate. Contribution of β-diversity to regional diversity was similar for all species groups with 22–25 %. Furthermore, some ponds hosted a large number of less frequent species and some endangered species, indicating that the conservation of biodiversity of fish ponds must be established at a regional scale.     

Garden pond diversity: Opportunities for urban freshwater conservation

Urbanisation is increasing globally, degrading terrestrial and freshwater habitats and reducing faunal and floral richness. Whilst the potential for garden ponds to serve as important biodiversity resources in urban areas has been documented in a limited number of studies, quantifying the contribution of garden ponds to urban freshwater diversity has been largely neglected. This study aims to quantify the taxonomic richness, community composition and conservation value of aquatic macroinvertebrates in domestic garden and non-urban ponds. Taxonomic richness was significantly lower in garden ponds than non-urban ponds at an alpha and gamma scale. A greater richness of Odonata, Coleoptera, Gastropoda and Hemiptera were recorded in non-urban ponds. Garden ponds were found to support compositionally different macroinvertebrate communities compared to non-urban ponds, influenced by variation in water depth and conductivity. A total of 23 taxa were recorded from garden ponds only. Non-urban ponds had a significantly higher conservation value compared to garden ponds (87% of garden ponds were of low or moderate conservation value, while only 35% of non-urban ponds were in these categories). Although garden ponds currently support limited macroinvertebrate diversity and have lower conservation value, they contribute to the regional species pool and their potential to limit future urban biodiversity loss is significant. Given their high abundance and popularity within the urban landscape, clear guidance is required for pond-owners on how to best manage garden ponds to support and sustain biodiversity. For this to be achieved, research is required to increase fundamental understanding of urban pond ecology, and the development of evidence led garden pond management practices.     

Unravelling the correlates of species richness and ecological uniqueness in a metacommunity of urban pond insects

City ponds have the potential to harbour a rich biodiversity of aquatic insects despite being located in an urban landscape. However, our current knowledge on the correlates of pond biodiversity is limited and even less is known about the factors that influence the ecological uniqueness of urban ponds. The multiple environmental gradients, at different spatial scales, that may affect biodiversity and ecological uniqueness of urban ponds can thus be seen both as an opportunity and as a challenge for a study. In this study, we aimed to fill this gap by focusing on aquatic insect assemblages in 51 ponds in the Swedish city of Stockholm, using a metacommunity perspective. We found that species richness was primarily determined by the density of aquatic insects, water depth and proportion of buildings around the pond. The uniqueness of ponds was estimated as local contributions to beta diversity (LCBD), and it was primarily related to the proportion of arable land and industry around the ponds. With regard to the metacommunity we found two interesting patterns. First, there was a negative relationship between richness and LCBD. Second, biodiversity was spatially independent, suggesting that spatially-patterned dispersal did not structure species richness or LCBD. These last two patterns are important when considering conservation efforts of biodiversity in city ponds. We hence suggest that the conservation of insect biodiversity in urban pond should consider the surroundings of the ponds, and that high-richness ponds are not necessarily those that require most attention because they are not ecologically the most unique.     

Lotic dispersal of lentic macroinvertebrates

Little is known on dispersal of lentic macroinvertebrates. We quantified dispersal of lentic macroinvertebrates through pond connections in a highly connected pond system, and investigated how dispersal rates were affected by connection properties and time of the day (day, night). Furthermore, by comparing the composition of assemblages of dispersing macroinvertebrates with the macroinvertebrate assemblages of source ponds, we tested whether dispersal was neutral or a taxon-specific process. We found that many taxa dispersed through the pond connections. Taxa richness of the dispersing macroinvertebrate assemblage was proportional to taxa richness in the source ponds. The number of individuals that dispersed, however, was not related to source pond densities, possibly because of the highly patchy distribution of lentic macroinvertebrates within ponds. Elevated dispersal rates were recorded for Baetidae, Chironomidae and Physidae, indicating a taxon-specific use of pond connections as dispersal pathway. None of the physical properties of the connections affected dispersal. Macroinvertebrates dispersed more during the night than during daytime. Of seven tested families, Chaoboridae and Chironomidae showed higher dispersal during the night, probably resulting from diel vertical migration, since pond connections mainly transported near-surface water. Flying and non-flying invertebrates dispersed equally frequent through pond connections. For non-flying invertebrates that disperse infrequently over land, dispersal through pond connections may provide an important additional means of dispersal.     

Freshwater diatom and macroinvertebrate diversity of coastal permanent ponds along a gradient of human impact in a Mediterranean eco-region

Mediterranean coastal areas are characterised by heavily transformed landscapes and an ever-increasing number of ponds are subjected to strong alterations. Although benthic diatoms and macroinvertebrates are widely used as indicators in freshwater ecosystems, little is still known about the diatom communities of lowland freshwater ponds in the Mediterranean region, and, furthermore, there are few macroinvertebrate-based methods to assess their ecological quality, especially in Italy. This article undertakes an analysis of benthic diatom and macroinvertebrate communities of permanent freshwater ponds, selected along a gradient of anthropogenic pressures, to identify community indicators (taxa and/or metrics) useful to evaluate the effect of human impacts. A series of 21 ponds were sampled along Tyrrhenian coast in central Italy. Five of these ponds, in a good conservations status and surrounded by woodland were selected as ‘reference sites’ for macroinvertebrates and epipelic diatoms. The remaining sixteen ponds were located in an agricultural landscape subject to different levels of human impact. The total number of macroinvertebrate taxa found in each pond was significantly higher in reference sites than in both the intermediate and heavily degraded ones, whereas the diatom species richness did not result in a good community variable to evaluate the pond ecological quality. The analysis revealed a substantial difference among the compositions of diatom communities between reference ponds and degraded ponds. The former were characterised by the presence of several species belonging to genera, such as Pinnularia sp., Eunotia sp., Stauroneis sp., Neidium sp., all of which were mostly absent from degraded ponds. Furthermore, the taxonomic richnesses of some macroinvetebrate groups (Odonata, Ephemeroptera, Trichoptera, Coleoptera), and taxa composition attributes of macroinvertebrate communities (total abundance, percentages of top three dominant taxa, percentages of Pleidae, Ancylidae, Hirudinea, Hydracarina) significantly correlated with variables linked with anthropogenic pressures. The results of the investigation suggested that diatoms tended more to reflect water chemistry through changes in community structure, whereas invertebrates responded to physical habitat changes primarily through changes in taxonomic richness. The methodologies developed for the analysis of freshwater benthic diatom and macroinvertebrate communities may have a considerable potential as a tool for assessing the ecological status of this type of water body, complying with the European Union Water Framework Directive 2000/60/EC. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16 May 2008     

Insect diversity in Gonggeom‐ji,the first protected paddy field wetland in Korea

Gonggeom‐ji pond is the first protected paddy field wetland area, designated by the Ministry of Environment of Korea in 2011, because of its high biodiversity and historic value. It contains reservoirs, paddy fields, and a forest site that provides diverse niches for insects. Quantitative methods were used in this study to estimate the insect diversity of this region. A transect of 50 m was designated in each site (reservoirs, paddy fields, and a forest site). Data were collected using sweeping and pitfall traps along each transect in May, August, and November 2017, representative of the seasons—spring, summer, and autumn, respectively. As a result, a total of 1079 individual insects representing 170 species from 60 families within nine orders were collected. Diversity, richness, and evenness indices were the highest in the forest site in May (4.77, 8.6, and 0.91, respectively). The dominance index was the highest in the forest site in November (0.64). Similarity index was the highest in the reservoir in May and August (0.519). These results would help compare different sites and their vegetation to assess relationships between insects and habitats.     

Are cladoceran diversity and community structure linked to spatial heterogeneity in urban landscapes and pond environments?

Biodiversity patterns in cladoceran communities were investigated in urban waterbodies in relation with residential land use, pond management, and waterbody environments. We evaluated species richness in the pelagic and littoral zones of eighteen waterbodies of a large Canadian city. Gamma diversity (26 species) observed at a small scale in the urban survey was important comparatively to large-scale surveys of lakes. Beta diversity ranged from 1 to 8 species among waterbodies. We tested if littoral species greatly contributed to regional diversity in urban waterbodies. Littoral species (Chydoridae, Ilyocryptidae, Macrothricidae, Polyphemidae) accounted for 58% of the total species pool. We distinguished five cladoceran assemblages associated to different waterbodies (temporary ponds, permanent lakes, and wetlands). Cladoceran communities were more diverse and variable in permanent lakes than in temporary ponds. Changes in cladoceran species assemblages among waterbodies were driven by variations in waterbody size and phosphorus enrichment, macrophyte and algal biomass, urban density, pond management practices, and the presence of potential predators as fish and macroinvertebrates. Our study indicates that both artificial ponds and lakes and natural wetlands are valuable habitats for the conservation of cladoceran biodiversity and rare endemic species in urban regions. Further research on pond management strategies promoting urban aquatic biodiversity should be undertaken.     

Urban ponds as an aquatic biodiversity resource in modified landscapes

Urbanization is a global process contributing to the loss and fragmentation of natural habitats. Many studies have focused on the biological response of terrestrial taxa and habitats to urbanization. However, little is known regarding the consequences of urbanization on freshwater habitats, especially small lentic systems. In this study, we examined aquatic macro‐invertebrate diversity (family and species level) and variation in community composition between 240 urban and 782 nonurban ponds distributed across the United Kingdom. Contrary to predictions, urban ponds supported similar numbers of invertebrate species and families compared to nonurban ponds. Similar gamma diversity was found between the two groups at both family and species taxonomic levels. The biological communities of urban ponds were markedly different to those of nonurban ponds, and the variability in urban pond community composition was greater than that in nonurban ponds, contrary to previous work showing homogenization of communities in urban areas. Positive spatial autocorrelation was recorded for urban and nonurban ponds at 0–50 km (distance between pond study sites) and negative spatial autocorrelation was observed at 100–150 km and was stronger in urban ponds in both cases. Ponds do not follow the same ecological patterns as terrestrial and lotic habitats (reduced taxonomic richness) in urban environments; in contrast, they support high taxonomic richness and contribute significantly to regional faunal diversity. Individual cities are complex structural mosaics which evolve over long periods of time and are managed in diverse ways. This facilitates the development of a wide range of environmental conditions and habitat niches in urban ponds which can promote greater heterogeneity between pond communities at larger scales. Ponds provide an opportunity for managers and environmental regulators to conserve and enhance freshwater biodiversity in urbanized landscapes whilst also facilitating key ecosystem services including storm water storage and water treatment.     

Patterns in the organization of Cerrado pond biodiversity in Brazilian pasture landscapes

There is a worldwide concern on the loss of pond biodiversity in human dominated landscapes. Nevertheless, agricultural activities appear to increase pond number in the Brazilian Cerrado through damming streams for cattle raising. These man-made ponds may represent important landscape features, but their importance to regional biodiversity has not yet been studied. Here, we evaluated differences in alpha and beta diversity under a multi-taxonomic approach, as well as tested pond size as the main driver of local species richness. We also assessed the importance of environmental heterogeneity through the analysis of the regional species accumulation curves (SAC). The overall result suggests that species turnover was the major component of regional biodiversity for all groups. Major physical and chemical water conditions had no effects on algae, macrophytes, water bugs, and birds species richness. Pond size had a significant effect on Odonata and fish species richness, while water beetles and amphibians were influenced by trophic conditions. Results from regional SAC show variations among different taxonomic groups regarding landscape heterogeneity: only algae, fish, and birds do not reached to an asymptote and had higher z-values. Our results highlight the importance of ponds for biodiversity conservation in increasingly agricultural landscapes in central Brazil.     

Elevational patterns and hierarchical determinants of biodiversity across microbial taxonomic scales

Microbial biogeography is gaining increasing attention due to recent molecular methodological advance. However, the diversity patterns and their environmental determinants across taxonomic scales are still poorly studied. By sampling along an extensive elevational gradient in subarctic ponds of Finland and Norway, we examined the diversity patterns of aquatic bacteria and fungi from whole community to individual taxa across taxonomic coverage and taxonomic resolutions. We further quantified cross‐phylum congruence in multiple biodiversity metrics and evaluated the relative importance of climate, catchment and local pond variables as the hierarchical drivers of biodiversity across taxonomic scales. Bacterial community showed significantly decreasing elevational patterns in species richness and evenness, and U‐shaped patterns in local contribution to beta diversity (LCBD). Conversely, no significant species richness and evenness patterns were found for fungal community. Elevational patterns in species richness and LCBD, but not in evenness, were congruent across bacterial phyla. When narrowing down the taxonomic scope towards higher resolutions, bacterial diversity showed weaker and more complex elevational patterns. Taxonomic downscaling also indicated a notable change in the relative importance of biodiversity determinants with stronger local environmental filtering, but decreased importance of climatic variables. This suggested that niche conservatism of temperature preference was phylogenetically deeper than that of water chemistry variables. Our results provide novel perspectives for microbial biogeography and highlight the importance of taxonomic scale dependency and hierarchical drivers when modelling biodiversity and species distribution responses to future climatic scenarios.     

Patterns of composition and species richness of crustaceans and aquatic insects along environmental gradients in Mediterranean water bodies

Differences in the dynamics of ecological processes between Mediterranean and colder temperate aquatic systems could imply different patterns in faunal communities in terms of composition and biodiversity (i.e. species richness and rarity). In order to identify some of these patterns the crustacean and aquatic insect composition and biodiversity of four water body types, classified according to their salinity and water permanence, were compared. Moreover, the relationships between species richness and water, pond and landscape variables were analysed. A total number of 91 water bodies located throughout Catalunya (NE Iberian Peninsula) were sampled. Three species assemblages were observed: one for permanent freshwaters, another for temporary freshwaters, and a third one for saline waters (SW), since permanent and temporary saline water bodies had similar composition. Differences in salinity were associated with proportion of crustaceans versus insects and with singularity. Thus, saline ponds had a higher proportion of crustaceans, and lower values of singularity. Conductivity was significantly related to total (crustaceans plus insects) richness, and also related to insect richness. The main difference between the models obtained for crustacean species richness and insect species richness is the significance of landscape variables in the latter, and this fact could be related to the different dispersion types of these two faunal groups: active for insects versus passive for crustaceans. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) alters its feeding niche in response to changing food resources: direct observations in simulated ponds

We used customized fish tanks as model fish ponds to observe grazing, swimming, and conspecific social behavior of common carp (Cyprinus carpio) under variable food-resource conditions to assess alterations in feeding niche. Different food and feeding situations were created by using only pond water or pond water plus pond bottom sediment or pond water plus pond bottom sediment and artificial feeding. All tanks were fertilized twice, prior to stocking and 2 weeks later after starting the experiment to stimulate natural food production. Common carp preferred artificial feed over benthic macroinvertebrates, followed by zooplankton. Common carp did not prefer any group of phytoplankton in any treatment. Common carp was mainly benthic in habitat choice, feeding on benthic macroinvertebrates when only plankton and benthic macroinvertebrates were available in the system. In the absence of benthic macroinvertebrates, their feeding niche shifted from near the bottom of the tanks to the water column where they spent 85% of the total time and fed principally on zooplankton. Common carp readily switched to artificial feed when available, which led to better growth. Common carp preferred to graze individually. Behavioral observations of common carp in tanks yielded new information that assists our understanding of their ecological niche. This knowledge could be potentially used to further the development of common carp aquaculture.     

Are distribution patterns linked to dispersal mechanism? An investigation using pond invertebrate assemblages

1. Dispersal ability influences the distribution and abundance of organisms, but empirical investigations of the relationship between dispersal ability and the composition of ecological assemblages are scarce. Here, we compare between-site variation in the species richness and community composition of actively and passively dispersing pond invertebrates.
2. Coleoptera (active dispersers) and microcrustacea (passive dispersers) were sampled over a season from 16 ponds within a 4-km radius in south-west England. Species richness and community composition were related to environmental variables using regression and Canonical Correspondence Analysis (CCA), respectively.
3. Coleopteran species richness was significantly and positively correlated with pond permanence and maximum area, whereas microcrustacean species richness was relatively equal across sites and did not correlate with environmental variables. The frequency of species' occurrence between sites was the same for both groups, which suggests that active and passive dispersers exhibited the same degree of dispersal.
4. Between-site variation in community composition was non-random for both groups, with pond permanence and area, together, explaining similar proportions of between-site variation for Coleoptera. Permanence was correlated most strongly with microcrustacean community composition and a high proportion (25%) of microcrustacean species were more numerous in smaller, more ephemeral ponds.
5. These data suggest that, at small spatial scales, Coleoptera which can undertake multiple dispersal events, are more likely to colonise large, more permanent ponds than passively dispersing microcrustacea. For microcrustacea, other traits (in this case those permitting existence in ephemeral habitats) may over-ride the influences of dispersal in driving between-site variation in species composition.     

Geometry of biodiversity patterning: assemblages of benthic macroinvertebrates at tributary confluences

We assessed whether tributaries in upland catchments (=watersheds) affected assemblages of benthic macroinvertebrates in mainstems, as has been reported in northern hemisphere systems. Eight confluences of small to medium streams (stream orders 1–4, 2.2–10.8 m wide) were studied in the Acheron River basin in Victoria, Australia. For each confluence, two transects were sampled at each of five zones relative to the confluence: two zones upstream in the mainstem, one zone upstream in the tributary, one zone at the confluence and one zone downstream in the mainstem. Surveys were conducted in both high-flow and low-flow conditions. In mainstems, there was no change in macroinvertebrate density, taxonomic richness or functional feeding group composition downstream relative to upstream of the confluences. While tributaries statistically had distinctive benthic macroinvertebrate assemblages compared to mainstems, these distinctions were small. In low flows, densities in tributaries were substantially lower than in mainstems, but densities during high flows were more similar (albeit only about one-third as high as in low flow) in tributaries and mainstems. An inverse pattern was evident for taxonomic richness, where richness in tributaries and mainstems was similar in low flows but was greater in mainstems than in tributaries in high flows. We found little evidence of tributary effects in macroinvertebrate assemblages in this basin, which is at odds with some previous results from other continents. To explain this divergence, we suggest a conceptual model outlining factors that control variation in effects of tributaries on assemblages of benthic macroinvertebrates in mainstems.     

Effects of land use on aquatic macrophyte diversity and water quality of ponds

1. Aquatic macrophyte diversity and water quality of 55 ponds in western Japan were related to land use and morphometric variables to identify the environmental factors that sustain biodiversity and the spatial extent at which these factors operate. 2. The relevant spatial extent for floating‐leaved macrophyte richness (500 m from pond edge) was larger than that for submerged macrophyte occurrence (10, 75 and 100 m), whereas emergent macrophyte richness was best explained at much larger extents (1000 m). Total macrophyte richness was explained at the extent of 500, 750 and 1000 m. The extents relevant for explaining the physicochemical condition of pond water (100 and 250 m) were similar to those for submerged and floating‐leaved macrophytes, suggesting that these two growth forms are more sensitive to water quality compared to emergent macrophytes. 3. Diversity of all three growth forms and that of total macrophytes collectively were inversely related to turbidity and nutrient concentration; among the three growth forms, submerged macrophytes were most affected by water quality. 4. Negative relationships were found between the proportion of urban area and the diversity of the three growth forms and that of total macrophytes and water quality. Species richness of emergent, floating‐leaved and total macrophytes decreased with depth and increased with surface area up to about 5000 m², above which it declined. 5. Urbanisation and enlargement of ponds were the two main factors that decreased aquatic macrophyte diversity in irrigation ponds. To alleviate the adverse effects of urban areas on aquatic macrophyte diversity, our results suggest that management efforts should focus on the creation of buffer zones within the relevant spatial extent from the pond edge.     

Effects of environmental factors on the species composition of aquatic insects in irrigation ponds

Although irrigation ponds contribute to the conservation of aquatic biodiversity, they have experienced declines in recent years. We therefore examined the relationships between various environmental factors and the community composition of aquatic insects, specifically insect predators, in irrigation ponds to gain knowledge that would aid in the conservation and restoration of biodiversity. We selected Odonata, Hemiptera and Coleoptera as target taxonomic groups and conducted censuses of these groups in 21 ponds in Shiga, central Japan. In total, we collected 30 and 10 species (or species groups) of Odonata and Hemiptera, respectively, and 17 species of Coleoptera. A partial canonical correspondence analysis revealed that the following four environmental factors significantly affected the species composition of aquatic insect communities: the number of emergent plant species, percent concrete revetment, presence of litter and peripheral length. Among these variables, the number of emergent plant species was the most potent factor, perhaps because emergent plants serve as sites for oviposition and emergence, and provide refugia for aquatic insects (odonate nymphs in particular). In contrast, some species specifically inhabited sites poor in emergent plants. This study shows that reductions in concrete revetments are necessary for the conservation of biodiversity. This would lead to increases in the number of aquatic plant species, which provide habitats and oviposition sites for many aquatic insects. Furthermore, to enrich the local biodiversity of aquatic insects, groups of irrigation ponds with different environments are needed.     

Diversity assessment of benthic macroinvertebrates, yeasts, and microbiological indicators along a longitudinal gradient in Serra do Cipó, Brazil.

The main goals of this study were: 1) to evaluate the structure, diversity, and functional trophic group composition of benthic macroinvertebrate communities; 2) to characterize water quality in the headwaters of the Doce river watershed, based on physical, chemical, and biological parameters (benthic macroinvertebrates, fecal coliforms, heterotrophic bacteria, and yeasts); and 3) to contribute to the knowledge of the structure and function of longitudinal gradients in lotic ecosystems in Brazil. A total of 60 benthic macroinvertebrate taxa were identified, the dominant group being the aquatic insects, with 50 families distributed in 8 orders. The dry period presented higher values of taxonomic richness and total density of benthic macroinvertebrates. A decreasing gradient was observed in these variable values from the 3rd order stretch down to the 6th order stretch. The highest Shannon-Wiener diversity values were found in the rainy period in the 3rd order stretches, which presented well-developed riparian forest. Besides the 3rd order stretches, the Pielou evenness index values were also high in the 6th order stretch. The collectors, together with the scrapers, predominated in the benthic macroinvertebrate communities in all river stretches, except in the 2nd, 4th, and 5th order stretches in the rainy period, where communities were dominated by filterers. The shredders and predators presented low densities for all river stretches. All microbiological variables presented low levels. Due to the high counts of heterotrophic bacteria and coliforms, the studied river stretches presented inadequate potability but adequate balneability levels. The results suggest that the structure, diversity, and composition of the benthic macroinvertebrate communities are influenced by the trophic resource availability, seasonality, and sediment heterogeneity. The microbiological results of this study allow inferring that the waters from Serra do Cipó have excellent potential for recreational use and as future sources of water for human consumption.