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The spatially hierarchical stream hydrogeomorphology classification presented by Cox et al. ([3]), based on 42 Irish headwater streams, is simple to apply and may be applicable across northern and western Europe with similar climate - landscape conditions. It is clear from these papers and others presented at SEFS12 that the extensive length of the small stream network and high numbers of ponds poses challenges in terms of water quality and biodiversity monitoring. Small water bodies are increasingly recognised as important for biodiversity and in terms of their influence on downstream water quality and contributions to catchment ecosystem services (Riley et al., [12]). [Extracted from the article]

Monitoring the condition (water quality, biodiversity, hydromorphology) of small water bodies presents a challenge for the relevant authorities in terms of time and resources (labour and financial) due to the extensive length of the stream network or the sheer number of small standing water bodies. Citizen science can help address information gaps, but the effort required should not be underestimated if such projects are to generate reliable and sustained data collection. The overall aim of this paper is to propose a framework for operationalisation of citizen science targeting collection of data from small water bodies. We first consider the data gaps and the elements (water chemistry, ecology, hydromorphology) to be addressed, in order to define where citizen science could best make an impact. We review examples of tools and methods that are appropriate for small water bodies, based on experience from a selection of freshwater citizen science projects, and the support that is needed for effective and sustained small water body projects across Europe. [ABSTRACT FROM AUTHOR]

In species with complex life cycles, such as anuran amphibians, several traits are influenced by ecological factors during ontogeny. The anuran Physalaemus nattereri shows an aquatic spawning behavior, placing foam nests at the edges of a pond where the water contacts land, exposing tadpoles to dehydration once the pond dries. P. nattereri tadpoles are known to present an intermediate ability to survive out of water when compared to other species reproducing in permanent or temporary ponds. A decrease in size of tadpole tails has been suggested to represent a response to cope with dehydration stress, but might impair swimming performance. We investigated the effect of dehydration on morphological traits, focusing especially on tail proportions, as well as burst swimming speed. P. nattereri tadpoles were exposed to hydric stress on moist paper substrates and morphology and locomotor performance was compared within the same individuals before and after hydric stress. Our experiment showed that morphological changes induced by hydric stress were directly related to swimming performance. Individuals having smaller tails, due primarily to contractions of the medial to distal tail portions, exhibited reduced times to reach burst speed and reduced burst speeds. [ABSTRACT FROM AUTHOR]

In Europe, ponds are an exceptionally numerous and widely distributed landscape feature forming a major part of the continental freshwater resource and contributing significantly to freshwater biodiversity conservation. This has been reflected by a growing scientific concern over the first few years of the twenty-first century and is evidenced by an increasing number of academic publications on pond related topics, particularly those relating to biodiversity. It is essential, however, that this expanding scientific knowledge is widely disseminated to those involved with pond management and is then rapidly translated into action. Inevitably, the task of transferring science to practice remains a significant challenge. As a first step towards meeting this challenge the European Pond Conservation Network (EPCN), at its biennial meeting in 2008 in Valencia (Spain), made this the main theme of the conference together with two special workshops further encouraging exchanges between scientists, practitioners and policy makers. The papers selected for this special issue of Hydrobiologia (from over 120 communications presented) are all from the conference. They represent a diverse collection of themes from across the continent and North Africa and present new and original insights into topics as wide ranging as: pond biodiversity; human disturbance; landscape ecology; ecological assessment and monitoring; practical management measures; ecological restoration; hydrology and climate change; invasive species and threatened species. In all cases, the papers demonstrate an overriding need for the development of a tight link between scientific knowledge and management. Furthermore, scientific advances have to be beneficial for on the ground management and, vitally, have to be disseminated, communicated and implemented into local, national and international policy. As such, national and international networks (such as the EPCN) have a central role to play and have to develop a robust information and communication strategy which will enable the dissemination of best practice materials and advice across the continent and beyond. The work contained in this volume represents a step in the right direction and will help to ensure that ponds remain a characteristic and highly visible feature of the European landscape in the twenty-first century. [ABSTRACT FROM AUTHOR]

In contrast to pelagic and benthic realms of the aquatic ecosystems, studies on the metaphytic habitats remain underrepresented in the literature. However, this realm may have a potential impact on composition and diversity of the open water assemblages through metacommunity processes (source-sink dynamics, mass-effect) especially in small ponds with extended littoral zone. Using a limnocorral experiment we studied how metaphyton affects diversity and composition of open water phytoplankton in a small eutrophic pond in the vegetation period. The three habitats (metaphyton, isolated and non-isolated open water) showed considerable differences in their taxa and functional group composition. Abundance-based diversity measures did not reveal remarkable differences among the assemblages of the three habitats. However, taxonomic and functional richness of the metaphyton and the non-isolated part of the pelagial significantly exceeded that of the limnocorral. Incidence-based similarity index values also showed closer resemblance of the metaphyton and plankton samples compared to that of the limnocorral. In the case of several functional groups, their functional redundancy in the metaphyton exceeded that in the open water areas. These results suggest that the metaphyton provides a refuge for several euplanktic elements that survive in the littoral and occasionally enrich the phytoplankton of the open water areas, representing that a within–lake metacommunity processes shape the composition and functioning of the open water areas in standing waters. [ABSTRACT FROM AUTHOR]

Urbanisation is one of the greatest threats to freshwater biodiversity, with the area of land covered by towns and cities predicted to increase significantly in the future. Ponds are common features in the urban landscape and have been created for a variety of reasons ranging from ornamental/amenity purposes through to the detention of urban runoff and pollution. This paper aims to quantify the aquatic macroinvertebrate biodiversity associated with garden, ornamental and other urban ponds in Leicestershire, UK. We examined the macroinvertebrate biodiversity of 41 urban ponds (13 garden, 12 park and 16 other urban ponds) within the town of Loughborough, UK. Park ponds supported greater macroinvertebrate richness than garden or other urban ponds. Garden ponds were the most taxon poor. Pond size was strongly correlated with macroinvertebrate diversity. Collectively, urban ponds were found to be physically and biologically heterogeneous and were characterised by high community dissimilarity. Urban ponds provide a diverse range of habitats for a mixture of common and rare aquatic macroinvertebrate taxa and represent a valuable biodiversity resource within anthropogenically dominated landscapes. Recognition of the significant contribution of ponds to urban freshwater biodiversity is important for future aquatic conservation within anthropogenically dominated landscapes. [ABSTRACT FROM AUTHOR]

Large branchiopods are a key component of the fauna of temporary ponds and play an important role in the functioning of these vulnerable ecosystems. Owing to the establishment of new settlements and agricultural expansion, temporary ponds in Tanzania are disappearing at an alarming rate whilst little is known about their diversity and ecology. We contrasted temporary ponds from a protected area with those in communal lands to detect associations between land-use types and large branchiopod community structure. Six large branchiopod species were collected, five of which have been previously reported from Southern Africa, whilst one turned out to be new to science: Streptocephalus manyarensis n.sp. Kafula and Brendonck (2023). The clam shrimp Cyzicus sp., fairy shrimps Streptocephalus lamellifer Thiele (1900) and S. bourquinii Hamer and Appleton (1993) were the most abundant and widely occurring. Variation in large branchiopod community structure was explained by the presence of Nothobranchius killifish and orthophosphate concentration. The large branchiopod community structure was different in settlement and protected areas. Our study on the occurrence and structure of large branchiopod communities in relation to land-use types serves as a base for formulation of guidelines and management tools to regulate land-use practices adjacent to temporary pond ecosystems. [ABSTRACT FROM AUTHOR]

Ponds and "pondscapes" (networks of ponds) are crucial habitats for biodiversity and for delivering multiple benefits to humans, so-called "Nature's Contribution to People", such as climate mitigation and adaptation to climate change, creation, and maintenance of habitat for biodiversity, water purification, flood mitigation and cultural benefits (e.g., recreational possibilities). However, ponds are not often considered as Nature-based Solutions to provide all these benefits. In addition, there is insufficient knowledge on how to manage and restore ponds to maximise their role to increase the resilience of ecosystems and society to climate change. To facilitate improved implementation of ponds as Nature-based Solutions for the delivery of a wide range of Nature Contributions to People, it is important to generate and integrate biodiversity, ecosystems, societal, economic and policy knowledge. Hence, there is a need for evidence-based guidance to support the broader use of ponds. Here, we review the role of ponds and pondscapes in delivering Nature's Contributions to People and provide an overview of the challenges and opportunities for their broader implementation as Nature-based Solutions. Finally, we propose a conceptual framework that can help the implementation of pond Nature-based Solutions, and that outlines future research needs. [ABSTRACT FROM AUTHOR]

Ponds are aquatic habitats defined by their small size. Although small they are found on every continent, they are disproportionately rich in aquatic biodiversity, benefit terrestrial wildlife and have important ecosystem function benefits. One of these benefits might be carbon sequestration, a possibility suggested by (1) their abundance, (2) the intensity of their biogeochemical activity. Whilst greenhouse gas fluxes from ponds have been monitored widely, quantifying the stocks of organic carbon buried in sediment is a gap in our knowledge. Here we summarise measures of organic carbon in pond sediments cores from a diverse range of lowland ponds in England. We estimate a general measure of 9.38 kg OC in a 1 m2 × 20 cm block of pond sediment and scale this up to an overall estimate for Great Britain of 2.63 million tons of OC in pond sediment, with 95% CI of 1.41 to 3.84 million tons. The relationship between sediment carbon and gas fluxes remains a significant unknown. [ABSTRACT FROM AUTHOR]

Macrophytes are considered key components of aquatic ecosystems and they also provide multiple benefits for humans. In this review, I identified and exemplified 26 types of ecosystem services provided by macrophytes. The most important supporting services provided by these plants are related to nutrient cycling and provisioning of habitat, but macrophytes also participate in water cycling and gases production. The presence of macrophytes and their activity enhance water purification and disease control which are important regulating services. Provisioning services are provided in the form of food at the local and global scale (e.g., rice), fiber, biochemicals, natural medicine and ornamental resources. Cultural services are provided in the form of spiritual and religious artifacts and local knowledge systems of communities which depend on macrophytes for surviving. Other cultural services are associated with educational activities, art inspiration, esthetic values in aquatic gardens and ponds, uses for leisure, recreation and ecotourism. There is evidence that the efficiency of ecosystem functioning, the provision of ecosystem services and ecosystem stability is enhanced by macrophyte diversity. Because macrophyte communities provide important benefits for humans, their conservation and restoration, where necessary, are important for human well-being. [ABSTRACT FROM AUTHOR]

Freshwater ponds have long been an overlooked biodiversity store and changing types of land use and the land management practices has led to a steady decline in pond numbers. Establishing the regional extent of pond loss is the first step in identifying key areas for conservation action. This study calculated pond loss in the Severn Vale catchment UK since 1900. Identification of pond location and surrounding land use on historic and contemporary maps enabled a comparison of total number, density and distance between present day and historic ponds. 57.7% of ponds present in 1900 were lost and pond density declined from 7.3 to 4.5 ponds km−2 between 1900 and 2019. This resulted in a 24.6 m increase in the average distance between contemporary ponds. Land use was an important factor in determining pond loss. Although in 2019 the highest density of ponds are in rural areas, 62.3% of ponds lost were from agricultural settings (arable or pasture). Our results highlight the significant pond loss experienced in the Severn Vale since 1900 and provide a valuable baseline for pondscape restoration. The methods described are widely applicable to other regions either with a history of ponds or an environment that could sustain them. [ABSTRACT FROM AUTHOR]

The study investigated predation risk to pond-reared Nile Tilapia Oreochromis niloticus and African Catfish Clarias gariepinus by amphibians, whether this is driven by height of pond-side grass or pond proximity to surface-water source and how this varies with fish stocking options. Based on small-scale freshwater aquaculture farms in western Kenya, field surveys were conducted during three sampling seasons spread across 6 months. These involved the following: (1) a sociological survey of 29 fish farming households; (2) sampling of amphibians for density, species richness and encounter rates and (3) measuring grass height, pond dimensions and water-source proximity across 24 ponds. Overall, 131 individual frogs from three families were recorded in 78 encounters. Amphibian density increased with pond-side grass height, presumably increasing predation risk, but decreased with water-source proximity. Amphibian encounter rate also decreased with water-source proximity, but was unaffected by grass height, while species richness responded positively to pond-side grass height, but not to water-source proximity. Amphibian encounter likelihood was higher in tilapia-only than in catfish-only or tilapia and catfish ponds irrespective of habitat variables. We demonstrate here that management practices for mitigating fish loss to predatory amphibians should include trimming pond-side vegetation, siting ponds close-to-moderate distances from water-sources and including catfish in pond polycultures. [ABSTRACT FROM AUTHOR]

Ponds are among the world's most endangered freshwater ecosystems. A comprehensive knowledge of pond biodiversity is urgently required to inform effective pond management and conservation actions. Most studies about pond biodiversity focus on aquatic taxa, while the terrestrial biodiversity, especially of birds, has been little studied. Moreover, the few studies existing on pond biodiversity do not account for different detection rates of species, thus yielding biased results. Here, we apply a hierarchical Bayesian modelling technique to data obtained from visual censuses to estimate bird species richness associated with small ponds in a semiarid region, considering the imperfect detection of species. The model incorporates specific responses to site characteristics (pond typology), landscape (environmental heterogeneity) and at regional scale (mean annual precipitation). The studied ponds were used by two thirds of the terrestrial breeding bird community of the study region. Our modelling approach increased by an average of 7.5 species the observed site-specific richness. Drinking troughs supported a greater richness than other pond types. Environmental heterogeneity was positively related with species richness, whereas no clear relation was observed between richness and precipitation. In addition to ecosystem services provided by ponds to human welfare, our results suggest these small isolated habitats may act as key landscape elements for terrestrial birds in semiarid regions. [ABSTRACT FROM AUTHOR]

Organic matter processing controls the flow of carbon and nutrients through ecosystems. Heterotrophic metabolism within ponds is supported by both terrestrial leaf litter and autochthonous production. We investigated the potential for the priming of leaf litter decomposition in small ponds using microcosms. We incubated senescent tulip poplar (Liriodendron tulipifera) leaf discs in the dark for 130 days either in contact with eutrophic pond sediments or isolated from sediment contact. Leaves that had been in contact with the sediments were significantly less tough and lost more carbon mass following the incubation than leaves that were not in contact with the sediments, indicating that they were decomposing faster. We calculated a positive priming effect of the sediments of 42% and 77% based on the change in toughness and C mass loss, respectively. We further found that leaf discs that were in contact with the sediments had significantly less fungal biomass, measured as ergosterol mass, and less leaf-derived N in fungal biomass than the leaf discs isolated from the sediments. These results indicate that the presence of the more labile organic matter of the sediments alters the rate of organic matter mineralization and the cycling of nitrogen and carbon. [ABSTRACT FROM AUTHOR]

The great crested newt Triturus cristatus has declined across its range due to habitat loss, motivating research into biotic and abiotic species determinants. However, research has focused on populations in England and mainland Europe. We examined habitat and survey criteria for great crested newts in Scotland, with focus on a large, translocated population. Adult counts throughout the breeding season were obtained annually using torchlight surveys, and Habitat Suitability Index (HSI) assessed at created ponds (N = 24) in 2006 (immediately post-translocation) and 2015 (9 years post-translocation). In 2006, 'best case' HSI scores were calculated to predict habitat suitability should great crested newts have unrestricted access to terrestrial habitat. Abiotic criteria included in and omitted from current great crested newt survey guidelines were assessed using data recorded in 2015. Some ponds had improved HSI scores in 2015, but overall failure to meet predicted scores suggests management is needed to improve habitat suitability. Great crested newt activity was positively associated with moon visibility and phase, air temperature, and pH, but negatively correlated with water clarity. Importantly, our results indicate there are abiotic determinants specific to Scottish great crested newts. Principally, survey temperature thresholds should be lowered to enable accurate census of Scottish populations. [ABSTRACT FROM AUTHOR]

Lakes of the Andean páramo are critical water reservoirs for millions of people. Páramo ecosystems have experienced anthropogenic warming faster than the global average. Recent paleolimnological work from Cajas National Park (southern Ecuador) revealed striking shifts in diatoms and Cladocera linked to climate change. However, the impacts on shallow lakes (< 5 m deep), which are numerically dominant on the landscape, remain poorly understood. Here, we use paleolimnology to investigate cladoceran species changes and responses to climate change in three shallow waterbodies from Cajas. Each system supported abundant littoral Cladocera. The deepest site (~ 4 m) contained the highest proportion of pelagic taxa, while the shallowest (~ 0.3 m) contained almost exclusively littoral taxa. Cladoceran assemblages in these shallow lakes reflect littoral habitat, likely partly influenced by shifting precipitation, and in one site, construction of a small rock dam. The cladoceran assemblage shifts do not align with regional temperature increases and reduced wind speeds, contrasting the ecological responses previously recorded in nearby deeper lakes. Although these polymictic, ice-free shallow systems are not immune to climate-related change, algal and cladoceran assemblages in nearby deeper lakes are responding earlier and more sensitively to recent climate changes, largely through changes to lake thermal stratification regimes. [ABSTRACT FROM AUTHOR]

Carbon dioxide released in the atmosphere and dissolved in water leads to acidification. Relatively few studies have focused on fresh waters, where biocalcifying species are more readily impacted by changes in pH. Sensitivity to pH of an endangered calcium-demanding organism, the crayfish Austropotamobius pallipes, was investigated in the Pinail nature reserve, a natural system with 3000 permanent ponds, some inhabited by the crayfish and others not, originally due to human introduction. From the 14 chemical parameters measured in this study, the main limiting factor preventing crayfish establishment appears to be water acidity (pH < 6.8), which affects calcification, molting, growth and reproduction. We predict that 20% of the Pinail populations will disappear by 2060 due to freshwater acidification with the present level of fossil fuel consumption. Ongoing and future restoration projects for conservation of this heritage crustacean must select hard water with the highest water pH (> 7). [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) is a powerful method for assessing the presence and distribution of invasive aquatic species. We used this tool to detect and monitor several invasive crayfishes Procambarus clarkii, Orconectes limosus and Pacifastacus leniusculus present in, or likely to invade, the ponds of the Brenne Regional Natural Park. A previous study showed that the eDNA method was not very efficient in detecting P. clarkii. In the present study, we explored new improvements in the detection of invasive crayfish. We designed specific primers for each crayfish species, and set up an experimental mesocosm approach to confirm the specificity of the primers and the sampling protocol. We analysed samples taken from ponds in 2014 and 2015. We compared two qPCR protocols involving either SybrGreen or TaqMan assays. Using these same primers, we were able to detect crayfish eDNA with both assays during the mesocosm experiment. However, crayfish from field samples could only be detected by performing qPCR with a SybrGreen assay. We successfully monitored the presence of three invasive species of crayfish using eDNA. This method is a powerful tool for establishing the presence or absence of invasive species in various freshwater environments. [ABSTRACT FROM AUTHOR]

The production of diapausing eggs is an ecological strategy commonly used by zooplanktonic organisms to cope with adverse conditions in time-varying habitats. Traits related to diapause (e.g., the time spent in diapause, the hatching fraction of diapausing eggs, or the amount of reserves allocated to them) should be combined by natural selection to favor adaptation to particular habitat conditions, especially in relation to their hydrology. Indeed, trade-offs between these traits are likely to occur due to resource allocation. Here, we studied population differentiation in survival, hatching propensity, and the amount of lipid reserves stored in diapausing eggs of the rotifer Brachionus plicatilis. We studied populations from ponds varying in hydrological conditions and used pond area as a proxy of water permanence. We found differences among B. plicatilis populations in the three traits studied, but no relationship with pond area. A significant negative relationship between diapausing egg survival in the sediment and hatching fraction was observed. We also found a negative relationship between lipid content and survival. These trade-offs are discussed in relation to the risks experienced by the rotifers in a given habitat, their ability for long-term survival, and the potential to disperse and recolonize new habitats. [ABSTRACT FROM AUTHOR]

Ephemeral ponds are often dominated by species with both terrestrial and aquatic life phases. Such species have the potential to strongly alter the food web structure of ponds, particularly if they are predators. Here we experimentally tested the effects of salamander larvae ( Salamandra salamandra) on invertebrate communities in ephemeral forest ponds. We repeatedly split two ponds into salamander enclosure- and exclosure-segments, and compared the diversity and biomass of potential prey organisms. We used stable isotopes of carbon (δC) and nitrogen (δN) of resources and consumers to characterise the food web structure. The presence of salamander larvae did not affect abundances of culicid larvae, their preferred prey. The population dynamics of most insect larvae was independent of the presence of salamander larvae, and was instead driven by the timing of hatching and emergence. However, a significant reduction resulting from salamander predation could be detected in the less abundant chironomid larvae. There was no substantial alteration of the food web structure as indicated by stable isotopes. However, the stable isotope results suggest a strong trophic subsidisation from the terrestrial system, which is probably the reason for the weak top-down effects of the salamander larvae on the invertebrate food web. [ABSTRACT FROM AUTHOR]

The landscape of northern Poland is characterised by a very large number of ponds. Traditionally it has been assumed that their hydrology is determined by precipitation and evaporation, and that they are isolated from the adjacent river network. Recent studies, however, have shown that ponds contribute to river runoff for at least part of the year. Their existence is therefore additionally based on fluvial and underground water sources. In order to establish the principles of water circulation in typical ponds, we selected 14 ponds with seasonally intermittent streams. We measured water levels in these ponds and flows in the river segments that connect them. We also determined subsurface exchange fluxes from the water balance equation. Our results demonstrated that the hydrological functions of the ponds varied throughout the year and depended on the level of water storage in the pond's catchment. When the level of retention in the pond's catchment is low, the pond becomes a water body without surface outflow and a drainage base for groundwater. As the level of retention in the catchment rises, ponds develop surface outflows and reconnect with the river network. At this point, their main function becomes retention of water originating from subsurface and surface inflows. Any surplus water may be fed to underground or surface waters. [ABSTRACT FROM AUTHOR]

Small waterbodies, including ponds and small lakes, low-order streams, ditches and springs, are the most numerous freshwater environments globally, are critical for freshwater biodiversity and are increasingly recognised for their role in ecosystem service delivery. Small waters often represent the best remaining examples of intact freshwater habitats and are the most likely to remain unpolluted, often being a refuge for species which have disappeared from larger, more damaged, waterbodies. Practically all water-related ecosystem services are initially mediated by small waters and some, such as carbon cycling, may be dominated by them. Small waters are exposed to all the threats affecting larger waters, and some experienced only by small waters. Despite this, small waters remain the least investigated part of the water environment and are largely excluded from water management planning. We identify the priorities for research to underpin better protection of small waters and recommend policy actions needed to better integrate small waters into the management of catchments and landscapes. The primary requirements are to identify reliable monitoring programmes for small waters, develop effective measures to protect the biodiversity and ecosystem services they provide and ensure that regulators take full account of this critical part of the water environment. [ABSTRACT FROM AUTHOR]

In this investigation, hydrological time series of three ponds located in the province of Córdoba (southern Spain) at a daily scale has been analyzed. For the first time, a detailed evolution of the water level of Jarales, Conde, and Amarga ponds has been acquired by means of the installation of level loggers in the deepest point of each of the ponds. We have modeled the water level evolution using a simple one-dimensional model. Calibration of the model was very satisfactory in two of the ponds. The model was then setup and simulated for two future Scenarios: A (IPCC climate change scenario) and B (climate change + groundwater withdrawal within the basin). Two ponds were classified as discharge ponds, which are the hydrological regime of the majority of southern Spain's continental ponds. One was classified as a recharge pond. With regard to the results obtained in the simulations for Scenarios A and B, our results showed that IPCC scenario will reduce hydroperiod significantly in the three ponds, with a reduction of approximately 500 cm in the water level. With respect to groundwater withdrawal within the basins, results show a very high impact in the hydroperiod in Amarga and Conde ponds. [ABSTRACT FROM AUTHOR]

Considerable progress has been made using experimental approaches and spatial surveys to better understand and manage shallow lake ecosystems. Meanwhile, research on the environmental histories of shallow lakes has lagged behind paleolimnological studies conducted on deeper systems, with most studies on shallow systems being completed over the last decade or so. Although shallow lakes may pose additional challenges to paleoenvironmental assessments, these potential shortcomings can often be identified and addressed. Due to their size, shallow lakes may act as amplifiers for a variety of environmental stressors, while dampening others. This overview summarizes a few recent studies assessing the long-term effects of multiple stressors on shallow lake ecosystems, with a particular focus on Arctic and Sub-Arctic ponds. Issues related to climatic change (e.g., the rapid transformation of shallow ponds in polar regions), as well as recent paleolimnological studies using shallow lake sediments to track past flooding frequencies, assessing the effects of seabirds and other biovectors on terrestrial ecosystems, blending archaeology and paleolimnology, and investigating the paths and trajectories of different pollutants (e.g., contaminants from the burgeoning petroleum industry) are highlighted. Some potential avenues for future research are also discussed. [ABSTRACT FROM AUTHOR]

Trophic interaction between contiguous habitats is an understudied area despite their ecological importance. We tested four hypotheses related to the visit of foraging birds in temporary ponds inhabited by fish: the local characteristics of ponds influence the (1) abundance and (2) composition of foraging birds; (3) the number of foraging bird visits increases in higher fish abundance; and (4) pond characteristics lead to a non-random spatial structure of fish assemblage. We studied 18 temporary ponds in the floodplain area of Pantanal (center-west Brazil), where we measured environmental variables (pond size, depth, macrophyte coverage, and forest canopy coverage), recorded the number of foraging birds and sampled fish. Foraging birds' abundance and composition were mainly influenced by forest canopy coverage and pond size, corroborating our first and second hypotheses. The hypotheses 3 and 4 were rejected. Fish abundance was not correlated with higher number of visits of foraging birds and fish distribution was random. Local environmental variables did not affect significantly fish richness and composition. Our results suggest that the abundance of foraging birds and fish presence are determined by different assembly processes (deterministic vs. random), which may limit ponds selection by birds due to the uncertainty in fish distribution and ephemeral nature of temporary ponds. [ABSTRACT FROM AUTHOR]

Ponds are biodiversity hotspots, but pond conservation is hampered by problems auditing these small, often temporary, habitats. Data on temporal changes to the number of ponds in response to weather variations are lacking. Annual and seasonal changes to the numbers and area of wetted ponds in a lowland farm in England were surveyed by field walks between November 2010 and November 2013. Plant communities were recorded to identify variations in pond type between land-uses. The study period coincided with severe drought up until April 2012 followed by record breaking precipitation. The wetted areas of ponds in wetlands and dune slacks showed the strongest relationship with rainfall over the preceding 4-6 months, whilst the areas of ponds in arable or pasture fields varied more with rainfall in the previous month. Ponds from different land-uses supported different plant communities and all types added to the overall total site biodiversity. Plant communities of ponds in arable fields benefitted from the extreme wet summer of 2012. The results show that the number and area of ponds varied significantly between years and seasons and that different pond types in different land-uses may vary in their response to extreme weather. [ABSTRACT FROM AUTHOR]

In small shallow lakes and ponds, the clear-water state can generally be maintained at higher nutrient concentrations compared to larger shallow lakes. The main objective of this study was to identify thresholds for total phosphorus (TP), submerged vegetation cover and zooplankton size that determine biomanipulation success in peri-urban eutrophic ponds. Additionally, the relationship between transparency and TP is discussed with regard to similar relationships and thresholds reported for shallow lakes. Using classification trees, a threshold TP concentration of 0.300 mg P L was determined below which a clear-water state was generally maintained after biomanipulation. When the average TP concentration was >0.300 mg P L, the stability of the clear-water state largely depended on the presence of sufficiently large zooplankton (>0.87 mm) or a submerged vegetation cover of >82% at some point during the year. This threshold TP concentration is considerably higher than the threshold of 0.1 mg L which is generally suggested for longer-term success of biomanipulation in shallow lakes. Such threshold nutrient concentration is important when restoring ecological quality in eutrophic small lakes and ponds. Extended follow-up of biomanipulation success in eutrophic ponds could provide more insight into the feasibility of these thresholds on the longer term. [ABSTRACT FROM AUTHOR]

It has been proposed that communities change from r to K strategies during primary succession. However, because strong-flying organisms are expected to arrive first in newly created habitats and they show trait characteristics associated more often with K strategies, we hypothesized that the r to K trajectories would be more closely followed by flightless and poorly-flying organisms. Moreover, we expected that macroinvertebrate communities would converge in their functional composition due to deterministic forces while diverging as taxonomic assemblages due to stochastic drift and biotic interactions. However, we also expected that dispersal abilities of the organisms would affect these tendencies. To address these issues, macroinvertebrates were sampled from isolated manmade ponds of different ages (1-22 years old) constructed at reclaimed opencast coal mines. In accordance with our expectations, only flightless and poorly-flying organisms exhibited a slight shift from r to K strategies, the community taxonomically diverged along the primary succession gradient, and stochastic drift showed greater effects on strong-flying organisms. In contrast, the community did not converge in its functional composition. The weak differences observed among the macroinvertebrates from ponds of different ages suggested that limiting environmental conditions prevented the organisms from evolving to a more structured community. [ABSTRACT FROM AUTHOR]

The interlocking leaves of tank-forming bromeliads (Bromeliaceae) collect rainwater and detritus, thus creating a freshwater habitat for specialized organisms. Their abundance and the possibility of quantifying communities with accuracy give us unparalleled insight into how changes in local to regional environments influence community diversity in small water bodies. We sampled 365 bromeliads (365 invertebrate communities) along a southeastern to northwestern range in French Guiana. Geographic locality determined the species pool for bromeliad invertebrates, and local environments determined the abundance patterns through the selection of traits that are best adapted to the bromeliad habitats. Patterns in community structure mostly emerged from patterns of predator species occurrence and abundance across local–regional environments, while the set of detritivores remained constant. Water volume had a strong positive correlation with invertebrate diversity, making it a biologically relevant measure of the pools’ carrying capacity. The significant effects of incoming detritus and incident light show that changes in local environments (e.g., the conversion of forest to cropping systems) strongly influence freshwater communities. Because changes in local environments do not affect detritivores and predators equally, one may expect functional shifts as sets of invertebrates with particular traits are replaced or complemented by other sets with different traits. [ABSTRACT FROM AUTHOR]

The fifth conference of the European Pond Conservation Network (Luxembourg, June 2012) brought together researchers, environmental managers, and other stakeholders with the aim to share state-of-the-art knowledge on the ecology, management, and conservation of ponds in the context of the many challenges facing the wider water environment. Although well-known ecological patterns apply to most ponds in Europe and elsewhere, recent data highlight that part of the environmental variables governing pond biodiversity remain specific to climatic/biogeographic regions and to elevation ranges, suggesting that, in addition to common practice, management plans should include range-specific measures. Beyond the contribution of individual ponds to the aquatic and terrestrial life, connected networks of ponds are vital in the provision of new climate space as a response to global climate change, by allowing the observed northward and/or upward movements of species. In terms of services, ponds offer sustainable solutions to key issues of water management and climate change such as nutrient retention, rainfall interception, or carbon sequestration. While the ecological role of ponds is now well-established, authoritative research-based advice remains needed to inform future direction in the conservation of small water bodies and to further bridge the gap between science and practice. [ABSTRACT FROM AUTHOR]

Freshwater predatory insects can exert strong effects on prey, although how multiple similar predators may coexist is not well understood. Larval predaceous diving beetles are often numerically and taxonomically abundant predators in lentic systems, but the proximate mechanisms that explain their high abundance remain unknown. Field surveys were conducted twice in June in ponds in Alberta, Canada to assess the associations between larvae of two genera ( Graphoderus, Rhantus), their spatial locations, and correlations with potential prey. Both larvae were common and positively correlated within wetlands although neither varied with pond depth nor distance from edge. Laboratory trials indicated that Graphoderus consumed more prey (corixids) at the surface, whereas Rhantus killed benthic prey (chironomids) and corixids at an equal rate; damselflies were the least consumed prey. Predation also varied with depth, with both larvae feeding at higher rates in the shallowest environments compared to Graphoderus at an intermediate depth. Predator-prey correlations from ponds were mostly congruent with predation trials; Graphoderus was positively correlated with corixids, Rhantus was positively correlated with corixids and chironomids; beetles were uncorrelated with damselflies. Reliance on different prey in different microhabitats may be an important mechanism for the maintenance of high abundance of dytiscid larvae. [ABSTRACT FROM AUTHOR]

Two beaver ponds in central New York State, one in a forested and one in an agricultural setting, were studied to determine the influence of nutrient enrichment on metabolic activity in small, shallow north temperate lentic systems with extensive littoral zones. Metabolic activity was determined from every 15-min oxygen measurements during the growing season utilizing a sonde and wind, temperature, and depth data. The agricultural Timmerman Pond was more enriched in phosphorus and nitrogen than the forested Hoxie Gorge Pond, a factor likely driving the greater gross primary production (GPP) and more positive net ecosystem production (NEP) measured in Timmerman. Average daily GPP was over 3X greater for the more enriched pond and seasonal average NEP was positive in the enriched pond while negative for the forested pond. Daily GPP and NEP were positively correlated ( P < 0.001) with daily solar radiation at both ponds. The active metabolism of small ponds, the most abundant size class of lentic systems, further confirms the important role of inland waters in the transformation of carbon on a global scale. [ABSTRACT FROM AUTHOR]

Each year hundreds of salt-encrusted waterbirds, mainly Eared Grebes ( Podiceps nigricollis Brehm) die at evaporation ponds of the trona (soda ash) industry in southwestern Wyoming. Clinical investigations attributed the mortality to sodium toxicity because high levels of sodium were found in brains of grebes salvaged from the ponds. This was puzzling because natural history information shows that this species resides in saline and hypersaline environments for most of the year. In addition, field observations gave no indication that grebes at the ponds were ingesting salt or salt crystals. Further, the salt glands were not hypertrophied and gavage experiments showed that healthy birds were able to ingest trona pond water without ill effect. Carcasses immersed in pond water, however, attained brain sodium levels far exceeding those considered toxic within a few hours, indicating that the high levels considered as causal probably resulted from post-mortem events. We attribute the mortality to complications of salt encrustation, notably impaired thermoregulation. Other purported cases of sodium toxicity involving encrusted birds at industrial ponds or hypersaline situations may have a similar etiology. [ABSTRACT FROM AUTHOR]

Zooplankton grazing can potentially affect the biomass and composition of phytoplankton communities directly and indirectly. Low chlorophyll a concentration for a given TP concentration and simplified fishless food webs lead to the expectation that zooplankton community grazing rates are high in Subarctic regions; however, zooplankton community grazing rates have not been determined for Subarctic lakes/ponds. We estimated zooplankton community grazing rates on phytoplankton in 12 lakes and ponds in Wapusk National Park, Canada using a microcosm grazing experiment. Lakes and ponds differed in zooplankton taxonomic composition, Chl- a concentration, and zooplankton biomass. We found that the grazing rates on the total chlorophyll a (GR) ranged 0-13.7% grazed per day and the grazing rates on the edible (<30 μm, GR) chlorophyll a was 0 to 16.7% per day. GR increased with lake Daphnia and cladoceran biomass, as did GR, which also had a negative relationship with the total in-lake Chl- a. The calculated zooplankton grazing rates were within the range found for larger, temperate lakes. [ABSTRACT FROM AUTHOR]

Integrated Constructed Wetlands (ICWs) constitute an alternative way of cleansing water in agricultural areas to conventional water treatment plants. These pond systems integrate their water treatment capabilities with other functions such as biodiversity enhancement, carbon sequestration and landscape fit, by virtue of mimicking natural wetlands. ICWs have shown to have potential to enhance macroinvertebrate diversity in agricultural areas due to their unique design flexibility. We suggest that ICWs characterised by adequate shore sloping and presence of complex habitat mosaics, as well as other design considerations, would maximise the potential of these systems to enhance macroinvertebrate diversity. In addition, it would be highly beneficial to increase the total ICW area and to increase the total number of ponds in a system accordingly from a minimum of four to at least five. This article also highlights the need not only to develop policies that focus on the creation of ICWs but also to foster a number of management practices that rely on the active involvement of farmers. The inclusion of additional ponds in selected ICW systems could be the means to inform local communities as to the importance, attractiveness and conservation value of ponds. [ABSTRACT FROM AUTHOR]

An increasing focus of interest in ponds over the last two decades arose largely because of concerns at the loss of ponds in intensively developed landscapes. In the UK, pond numbers declined from approximately 800,000 in the nineteenth century to 200,000 by the 1980s. Since then pond numbers have started to increase. The focus on overall pond numbers overlooks the importance of the history and origins of different pond types. This study combines a detailed map based audit of pond numbers in south-east Northumberland, UK, recorded at seven time intervals since the mid-nineteenth century with a survey of contemporary plant communities in ponds with known and distinct histories to examine changes to numbers of ponds and communities associated with ponds with different origins. 222 ponds were recorded in the study area in the mid-nineteenth century, 257 in 2005/08. However, only 23 of the original ponds had survived with substantial losses and gains at all the map survey dates linked to changed land use from agriculture to coal mining then development of nature reserves and golf courses. Contemporary ponds on nature reserves, golf courses and subsidence ponds supported rather different plant communities to each other, with non-native invasives in golf and nature reserve sites, whilst individual reserves differed from one another perhaps due to intentional planting. Surviving old farm ponds were usually degraded. The results show that the history of ponds in a region can create an important cultural biodiversity which pond conservation strategies should incorporate. [ABSTRACT FROM AUTHOR]

Biomanipulation through fish removal is a tool commonly used to restore a clear-water state in lakes. Biomanipulation of ponds is, however, less well documented, although their importance for biodiversity conservation and public amenities is undisputed. In ponds, a more complete fish removal can be carried out as compared to lakes and therefore a stronger response is expected. Fish recolonization can, however, potentially compromise the longer term success of biomanipulation. Therefore, we investigated the impact of fish recolonization on zooplankton, phytoplankton, and nutrients for several years after complete drawdown and fish removal in function of submerged vegetation cover in 12 peri-urban eutrophic ponds situated in Brussels (Belgium). Fish recolonization after biomanipulation had a considerable impact on zooplankton grazers, reducing their size and density substantially, independent of the extent of submerged vegetation cover. Only ponds with <30% cover of submerged vegetation shifted back to a turbid state after fish recolonization, coinciding with an increase in density of small cladocerans, rotifers, and cyclopoid copepods. In ponds with >30% submerged vegetation cover, macrophytes prevented an increase in phytoplankton growth despite the disappearance of large zooplankton grazers. Our results suggest that macrophytes, rather than by providing a refuge for zooplankton grazers, control phytoplankton through other associated mechanisms and confirm that the recovery of submerged macrophytes is essential for biomanipulation success. Although the longer term effect of biomanipulation is disputable, increased ecological quality could be maintained for several years, which is particularly interesting in an urban area where nutrient loading reduction is often not feasible. [ABSTRACT FROM AUTHOR]

Differences among lake morphologies often explain variation in characteristics of lentic ecosystems. Although beaver ponds also vary in morphology, previous studies have not examined the effects of such variation on downstream ecosystems. This study evaluated downstream effects of multiple beaver ponds in the Colorado Rocky Mountains during one low and one high-flow year. Beaver pond morphology was described as the natural log transformed ratio of beaver dam height (which determines hydraulic head) to pond surface area and related to pond spillover phytoplankton and characteristics of the ecosystem downstream (nutrient concentrations, limiting nutrients, periphyton, benthic organic matter (BOM), and benthic invertebrate consumers). Nitrate concentration increased systematically downstream of beaver ponds, but only in the low flow year when groundwater influences predominated. Effects of beaver ponds on soluble reactive phosphorus concentration depended on pond morphology, increasing downstream of small ponds with high dams, but only during the low-flow year. In situ experiments showed that neither beaver activity nor pond morphology predicted periphyton-limiting nutrients downstream. Both periphyton biomass and BOM decreased downstream of small ponds with high dams but pond morphology did not predict abundance of invertebrate grazers or detritus-feeding consumers. While suspension feeding invertebrates increased downstream from small ponds with high dams, variation in chlorophyll a from water spilling over beaver dams did not follow a similar pattern. We conclude that the effects of beaver ponds on downstream nutrients, resources and consumers are rarely systematic, but instead depend on variation in pond morphology and on annual hydrologic variation. [ABSTRACT FROM AUTHOR]

A crucial component for developing insect management strategies is the understanding of the ecological parameters involved in habitat selection by proliferating species. The key ecological drivers underlying habitat selection in the mosquito Coquillettidia sp. have been investigated in natura. Vegetation analysis suggested that the most suitable habitats were ponds with a high vegetation cover maintaining a high degree of humidity in the air. The optimal biotope for Coquillettidia was associated with the presence of larval host plants such as Typha sp., Phragmites sp., and Juncus sp. Water quality was also found to be a key factor in larval habitat distribution. The presence of larvae was significantly correlated with physico-chemical factors and the optimal water characteristics were neutral pH, low salt concentration, and a relatively low level of suspended particulate matter. A significant correlation was observed between chemical cues and the Coquillettidia distribution pattern. For instance, 2,6-di- tert-butyl- p-cresol was positively correlated to larval habitat, whereas high lauric acid and heptadecanoic acid concentrations may be limiting factors. This study underlines the fact that mosquito habitat selection is driven by a complex process based on discriminating levels of several ecological factors. Multivariate analysis helps understand such processes, which is this case will assist in managing expanding populations of a species that threatens human health. [ABSTRACT FROM AUTHOR]

This study explores the past, present and future ecological changes in the highest Mediterranean temporary pond (Omalos pond) in western Crete, Greece. Data from downcore pollen analysis (including pollen and spores from both aquatic vegetation, and terrestrial herbaceous, arboreal and shrub vegetation), modern vegetation monitoring and existing climate scenarios have been combined to provide a picture of the ecological changes in the pond over the last 13,600 years. Downcore pollen analysis throughout the last 13,600 years indicated the presence of species typical of Mediterranean Temporary Pond (MTP) habitats and suggested relatively drier conditions towards the present. The low number of non-native, cultivated species (such as herbaceous Trifolium and Plantago species) observed over this period suggested relatively low impact from crop agriculture, despite the increasing grazing pressure in the area. In the absence of independent proxies, we cannot reliably distinguish between natural and human-induced changes. The presence of aquatic Isoetes in the palaeo-record indicates the existence of an ephemeral pond in the area as early as the beginning of the Holocene suggesting resilience of the ecosystem over time. However, the degraded state of pollen in depths over 55 cm (i.e. 3600 year BP) increases the uncertainty of the interpretation. Currently, the pond holds 76 plant species belonging to 25 families. Therophytes and chamaephytes were the most frequent, suggesting a typical ephemeral habitat life form spectrum. Species richness was found to increase during spring surveys whereas the highest turnover was observed between summer surveys of consecutive years. Cluster analysis demonstrated a distinct zonation in four vegetation belts from the periphery to the centre of the pond which is typical of these environments. Modelling, based on two IPPC scenarios (A2 and B2), predicted relatively low climate change impacts on the pond’s hydroperiod for the next 100 years (i.e. a decrease of 16 and 24 days, respectively). This reduction in the hydroperiod of the pond will have an effect on the physiognomy and spatial extent of vegetation, particularly for the transitional belts between the core and its outer area, while it will exert more pressure on the pond as a water resource for sheep in the region. However, cumulative effects and complex interactions of climate-driven environmental changes and other anthropogenic disturbances might act synergistically to accelerate impacts in the future. [ABSTRACT FROM AUTHOR]

Ponds support a rich biodiversity because the heterogeneity of individual ponds creates, at the landscape scale, a diversity of habitats for wildlife. The distribution of pond animals and plants will be influenced by both the local conditions within a pond and the spatial distribution of ponds across the landscape. Separating out the local from the spatial is difficult because the two are often linked. Pond snails are likely to be affected by both local conditions, e.g. water hardness, and spatial patterns, e.g. distance between ponds, but studies of snail communities struggle distinguishing between the two. In this study, communities of snails were recorded from 52 ponds in a biogeographically coherent landscape in north-east England. The distribution of snail communities was compared to local environments characterised by the macrophyte communities within each pond and to the spatial pattern of ponds throughout the landscape. Mantel tests were used to partial out the local versus the landscape respective influences. Snail communities became more similar in ponds that were closer together and in ponds with similar macrophyte communities as both the local and the landscape scale were important for this group of animals. Data were collected from several types of ponds, including those created on nature reserves specifically for wildlife, old field ponds (at least 150 years old) primarily created for watering livestock and subsidence ponds outside protected areas or amongst coastal dunes. No one pond type supported all the species. Larger, deeper ponds on nature reserves had the highest numbers of species within individual ponds but shallow, temporary sites on farm land supported a distinct temporary water fauna. The conservation of pond snails in this region requires a diversity of pond types rather than one idealised type and ponds scattered throughout the area at a variety of sites, not just concentrated on nature reserves. [ABSTRACT FROM AUTHOR]

The European Beaver, once widely distributed across Europe, was almost completely eradicated in the nineteenth century. In the meantime, it has recovered large parts of its distribution range and has increasingly resettled the valleys of the Central European Highlands. In the past, in these same valleys, countless artificial fish and fire-fighting weir ponds, with a water regime similar in size and location to those of the Beaver, were created. In order to assess how near-natural the newt communities of the artificial ponds are, we studied 21 artificial and 22 Beaver ponds in the Eifel, a typical Central European Highland in Germany, using funnel traps. In general, artificial and Beaver ponds supported the same eight amphibian species, whereby the Beaver ponds had on average a larger number of species (4.8 species as opposed to 3.6). The average population size of the two dominant Urodela species, determined by a mark-recapture method, was higher than is usually recorded in other pond types, whereby the influence of the factor “Beaver” pond proved to be either neutral ( Triturus alpestris) or positive ( Triturus helveticus). The decisive factor for the activity density of both species in the ponds studied was the presence of fish. Artificial ponds probably provide an important substitute for the once common Beaver ponds for at least the majority of woodland species in large areas of Central Europe. This leads to the following conclusions: [ABSTRACT FROM AUTHOR]

Manipulative experiments to test the short-term effect of oxygen depletion events on microbial activity and benthic fluxes in organic-rich sediments were carried out in March and June 2004. Oxic–anoxic transitions were induced by prolonged dark incubation of sealed sediment cores collected in phytotreatment ponds. Benthic fluxes of oxygen (O2), carbon dioxide (CO2), inorganic nutrients, and free sulfides were measured before (oxic) and after (anoxic) the transition occurred. A multifactorial design was employed for monitoring esoenzymatic activity, heterotrophic bacterial production, total prokaryotic abundance, actively respiring bacterial cells, and the biochemical composition of sedimentary organic matter. The oxic to anoxic transition resulted in a significant increase of esoenzymatic activity and bacterial production in March, due to the profound modification of the benthic community and the release of labile organic compounds which followed the onset of anoxia. In parallel, net efflux rates of dissolved inorganic carbon (DIC) and ammonium (NH4) sharply decreased, soluble reactive phosphorus (SRP) influx reversed, and sulfide was buffered within the oxidized sediments. From March to June, ponds evolved toward oxygen deficit and reducing conditions in the upper sediment horizon, losing benthic fauna and biogeochemical buffering capacity. Thus, the oxic to anoxic transition had a much smaller effect on microbial activity and net flux exchange, while S+) sharply decreased, soluble reactive phosphorus (SRP) influx reversed, and sulfide was buffered within the oxidized sediments. From March to June, ponds evolved toward oxygen deficit and reducing conditions in the upper sediment horizon, losing benthic fauna and biogeochemical buffering capacity. Thus, the oxic to anoxic transition had a much smaller effect on microbial activity and net flux exchange, while S2− was consistently delivered from the sediment to the water column. Overall data from this study suggest that the short-term response of benthic microbial activity and solute fluxes to anoxic events may have a significant impact on sediment biogeochemistry (e.g., at the oxic–anoxic interface), and that this impact may vary greatly depending on the sediment features, mainly its organic content and redox condition. [ABSTRACT FROM AUTHOR]

The aim of this research was to examine nutrient limitation of phytoplankton in solar salt ponds of varying salinity at Useless Inlet in Western Australia. These ponds use solar energy to evaporate seawater for the purpose of commercial salt production. A combination of techniques involving water column nutrient ratios, comparisons of nutrient concentrations to concentration of magnesium ions and bioassays were used in the investigation. Comparisons of changes in dissolved inorganic nitrogen to phosphorus ratios and concentrations of dissolved inorganic nutrients against changes in concentrations of the conservative cation Mg2+ indicated that phytoplankton biomass was potentially nitrogen limited along the entire pond salinity gradient. Nutrient addition bioassays indicated that in low salinity ponds, phytoplankton was nitrogen limited but in high salinity ponds, phosphorus limited. This may be due to isolation of phytoplankton in bioassay bottles from in situ conditions as well as to changes in phytoplankton species composition between ponds, and the variable availability of inorganic and organic nutrient sources. The differences in limiting nutrient between methods indicate that phytoplankton cells may be proximally limited by nutrients that are not theoretically limiting at the pond scale. Dissolved organic nutrients constituted a large proportion of total nutrients, with concentrations increasing through the pond sequence of increasing salinity. From the change in nutrient concentrations in bioassay bottles, sufficient dissolved organic nitrogen may be available for phytoplankton uptake in low salinity ponds, potentially alleviating the dissolved inorganic nitrogen limitation of phytoplankton biomass. [ABSTRACT FROM AUTHOR]

Gypsum crusts containing multicolored, stratified microbial communities develop in the evaporation ponds of a commercial saltern in Eilat, Israel at salt concentrations between 190 and 240 g l−1. The upper 0.5–2 cm of the crust is densely populated by orange-brown unicellular cyanobacteria. Below, a layer of green-colored filamentous cyanobacteria is found. Underneath, a bright purple layer of anoxygenic phototrophs is present, below which a reduced black layer is found. We have investigated the biological properties of this crust using a wide variety of techniques, and we here review the results of these interdisciplinary studies. The tests performed included microscopic examination of the biota, phylogenetic analyses based on 16S rRNA gene clone libraries and denaturing gradient gel electrophoresis, fatty acid analysis, light intensity and light quality measurements, microelectrode studies of oxygen profiles and oxygen evolution, determination of sulfate reduction using radioisotope methods, and measurement of methane evolution. The stable vertical stratification in the system enabled separate analyses of the different layers with a high spatial resolution. It was therefore possible to combine the different approaches and obtain information on the activities of the different types of oxygenic and anoxygenic phototrophs, dissimilatory sulfate reducers and methanogens in the different layers, as well as phylogenetic information on the nature of the microorganisms responsible for these processes. The gypsum crust thus becomes a paradigm for the study of a wide variety of microbial processes and their interrelationships in the presence of high salt concentrations. [ABSTRACT FROM AUTHOR]

We evaluated tadpole communities of temporary and permanent ponds, in order to understand how community richness varies monthly in a subtropical humid climate, to interpret the community structure in relation to biotic and abiotic environmental variables related to the temporary and permanent ponds. The study site was the Pró-Mata Research and Nature Conservation Center, a private reserve in southern Brazil. The climate is classified as Temperate Superhumid, with no dry season. We sampled three temporary and three permanent ponds. We compared the richness of tadpole assemblages of permanent and temporary ponds through individual-based rarefaction curves, and tested for possible differences using a MANOVA test. Tadpole richness was related to temporal environmental descriptors through General Regression Model. Relationships between the tadpole assemblages and possible predictors of their spatial variation were measured using a partial Canonical Correspondence Analysis. Analysis of rarefaction curves indicated higher expected richness for the temporary ponds. The mean values of richness were significantly different between the two hydroperiods across all months. Monthly richness showed the same tendency of variation for both pond types. Only temperature was related to tadpole richness. The pCCA analysis was significant. The most important predictors on the first pCCA axis were vegetation cover, conductivity, depth, and predator diversity. In this study, vegetation cover, conductivity, predator diversity, and water depth explained the spatial variation of tadpoles between ponds, with tadpole richness and diversity being higher in temporary than in permanent ponds. Our results suggest that different spatial-seasonal patterns operating in temporary and permanent ponds are related to maintaining the species diversity of pond-breeding anurans. [ABSTRACT FROM AUTHOR]

Fifty-five macroinvertebrate metrics were tested for their response to pond condition in 41 ponds of northwest Spain to develop a preliminary multimetric index for ecological assessment of Mediterranean flatland ponds. Stressor specific response of individual attributes to eutrophication and habitat alteration was also investigated to identify differences in the responses of metrics to single stressors and elucidate how this might affect the performance of the final index. Several combinations were tested using discrimination efficiency (25th percentile of slightly impaired sites for metrics decreasing with perturbation and 75th percentile of slightly impaired sites for metrics increasing with perturbation) and Mann–Whitney U-test with Bonferroni adjustment ( P < 0.001). The final index comprised five measures (generic richness of Chironominae, generic richness of Dytiscidae + Odonata + Tanypodinae, relative richness of Chironomidae, % Macropelopini and Shannon index) and discriminated between acceptable (good) and unacceptable (moderate) conditions with more than 86% efficiency. Moreover, all the five measures included in the final index showed unidirectional responses to eutrophication, decreasing as eutrophication increased. In contrast, the effect of habitat alteration was less clear, especially in ponds in best available conditions where a vegetation belt of shrubs and trees prevented growing of macrophitic vegetation on shores and consequently associated fauna. Interestingly, none of the functional groups (e.g. % predators and % collector–gatherers) were sensitive to degradation. [ABSTRACT FROM AUTHOR]

The effects of nutrient additions on aquatic systems have been frequently studied. Typically, these studies report an increase in algal biomass and a decrease in species diversity in response to nutrient increases. However, it is not clear why comparable aquatic communities respond differently to nutrient additions of similar magnitudes. We tested the effects of the rate and amount of nutrient load on community structure in 760 l mesocosms; treatments manipulated the total amount of nutrients that entered an aquatic system (small versus large load) and the temporal pattern in which these nutrients entered the system (annually, monthly, or weekly). We found that the effects of the loading rate of nutrients were at least as important as the total amount of the nutrients for several response variables. Although these effects were manifested in several ways, the response to the different rates was most prominent within groups of the primary producers, which showed large shifts in composition and abundance. [ABSTRACT FROM AUTHOR]

Aquatic predators and habitat permanence can jointly affect benthic invertebrate biomass and community composition. In 2006 I sampled fish and invertebrates in ten ponds embedded in a seasonal wetland before and after a natural drought. Drought reduced fish biomass and density leaving some ponds in a fishless condition when rains returned in July. In July, large aquatic insects and crayfish colonized and reproduced in the ponds, but did not colonize all of the ponds equally. Using measurements of fish abundance and other environmental parameters of the ponds, I conducted linear regression analyses to explore potential drivers of variable invertebrate biomass in July. Fish biomass had a negative effect on invertebrate biomass and it explained more of the variation in total invertebrate biomass and total non-shrimp biomass than fish abundance (number of fish caught). Dissolved oxygen and pond depth were both correlated with fish biomass, but were poorer predictors of invertebrate biomass. Ponds with few or no fish had 20× greater total biomass and 200× more non-shrimp biomass than ponds with high fish biomass. Shrimp dominated the invertebrate composition, and were only found in the two deepest ponds with the highest fish biomass; predatory insects and crayfish dominated the other eight ponds. When taxa were analyzed separately, fish biomass explained a large portion of the variation for predatory insects (Coleoptera, Hemiptera, and Odonata) and crayfish ( Procambarus alleni), but dissolved oxygen was the best predictor of larval stratiomyid (order Diptera) biomass. These results are generally consistent with studies demonstrating negative effects of fish on large predatory invertebrates, but also suggest that more severe local droughts can seasonally enhance insect and crayfish populations by generating fishless or nearly fishless conditions. [ABSTRACT FROM AUTHOR]

A new pond complex, designed to enhance aquatic biodiversity, was monitored over a 7-year period. The Pinkhill Meadow site, located in grassland adjacent to the R. Thames, proved unusually rich in terms of its macrophyte, aquatic macroinvertebrate and wetland bird assemblages. In total, the 3.2 ha mosaic of ca. 40 permanent, semi-permanent and seasonal ponds and pools was colonized by approximately 20% of all UK wetland plant and macroinvertebrate species over the 7-year survey period. This included eight invertebrate species that are Nationally Scarce in the UK. The site supported three breeding species of wading bird and was used by an additional 54 species of waders, waterfowl and other wetland birds. The results from four monitoring ponds investigated in more detail showed that these ponds significantly supported more plant and macroinvertebrate species than both minimally impaired UK reference ponds, and other new ponds for which compatible data were available. Comparisons of the physico-chemical, hydrological and land-use characteristics of the Pinkhill pools with those of other new ponds showed that the site was unusual in having a high proportion of wetlands in the near surrounds. It also had significantly lower water conductivity than other ponds and a higher proportion of (non-woodland) semi-natural land in its surroundings. Given that ponds are known to contribute significantly to UK biodiversity at a landscape level, and that several thousand new ponds are created each year in the UK alone, the findings suggest that well designed and located pond complexes could be used to significantly enhance freshwater biodiversity within catchments. [ABSTRACT FROM AUTHOR]