Lentic Freshwater Research Articles

Shifts in amphibian population dynamics in response to a change in the predator community

AbstractPredation can affect prey behavior, demography, abundance, and distribution, particularly in lentic freshwater ecosystems. Fish are predators known to reduce the abundance of their prey and to restrict the distribution of species. Using time series which spanned 43 and 22 yr, respectively, we analyzed the effect of a change in the fish predator community on the dynamics of two pond‐breeding amphibian populations (Rana temporaria and Rana dalmatina). Specifically, we used a state‐space time series model which allows for density dependence and observation error, to ask whether the change in predation risk affects population growth rate and the return point around which the populations fluctuate. The results showed that the type of observation error assumed did not affect the biological parameters. We found evidence for density dependence in both populations. The effect of the change in fish predation on population growth rate and the return point was strong in the population where fish invaded a previously fish‐free pond. The effect was weaker in the population where the change was from cyprinid fish to pike. The results showed that fish predation can have strong effects on amphibian population dynamics. The observed population dynamical pattern is phenomenologically similar to alternative stable states.

Differential use of artificial habitats by native and non-native fish species in Neotropical reservoirs

The use of artificial habitats as tool for management and conservation of lentic freshwater ecosystems has been most studied in North America, with dominance of Centrarchidae fish. Contrary to north temperate ecosystems, Cichlidae species appear to be prevalent on artificial habitats in Neotropical reservoirs. Currently, due to the rapid expansion of non-native fish introductions globally, these two fish families are increasingly expected to coexist in the same environments. This study aimed to test experimentally the use of artificial habitats by fish in two Neotropical reservoirs between: (i) kind of habitats, (ii) Cichlidae and Centrarchidae, (iii) native and non-native species, and (iv) size classes. The results showed a higher number of individuals and species in pipes and rocks habitats. The dominance of Cichlidae over Centrarchidae in pipes, rocks and control habitats suggests a kind of partitioning between these groups. Native Cichlidae (< 80 mm) were predominant in pipes whereas native and non-native species seemed to share tree and rock habitats. Artificial habitats can potentially increase local abundance and diversity of fish species, however, it is essential to consider the species’ origin (i.e. native or non-native) associated with each kind of artificial habitat in order to prevent invasive species from benefiting of artificial structures deployment in freshwater systems.

Benthic microalgae are more 13C-depleted than phytoplankton in temperate flooded rice fields

We investigated seasonal changes in the δ13C levels of particulate organic matter (POM), which mainly consist of phytoplankton and microphytobenthos from three flooded rice fields treated with different types of fertilizer (chemical NPK, chemical PK, or organic fertilizers) in northeast Japan. Generally, microphytobenthos in lentic freshwater systems show higher levels of δ13C (about− 26‰) than phytoplankton (about− 32‰) due to 13C enrichment under limited resources of dissolved inorganic carbon (DIC) in the benthic boundary layer (BBL). However, our results showed that POM was more 13C-enriched than microphytobenthos regardless of the type of fertilizer applied. Overall mean POM and microphytobenthos δ13C levels in the fields ranged from − 27.5 to − 25.2‰ and − 30.3 to − 27.0‰, respectively. In contrast, δ13C levels in soil organic matter were temporally stable, with means ranging from − 27.6 to − 26.3‰. High δ13C levels in POM were due to limited DIC under conditions of high phytoplanktonic productivity and water stagnation in paddy systems, resulting in DI13C intake during photosynthesis. Conversely, microphytobenthos used more 13C-depleted DIC in the BBL, which was microbially regenerated from the SOM pool. Microphytobenthos in the rice fields showed similar seasonal variations in δ13C, decreasing sharply in late June and then increasing again. This was possibly caused by changes in DIC availability or the growth rates of microphytobenthos during that period. The present results provide basal information about producer-specific δ13C variations in two major microalgal producer groups, phytoplankton and microphytobenthos, in temperate rice paddy wetlands.

Effects of metal nanoparticles on freshwater rotifers may persist across generations

Nanotechnology has become one of the fastest growing industries in the current century because nanomaterials (NMs) are present in an ever-expanding range of consumer products increasing the chance of their release into natural environments. In this study, the impacts of two metal nanoparticles (Ag-NPs and CuO-NPs) and their equivalent ionic forms (Ag+ and Cu2+) were assessed on the lentic freshwater rotifer Brachionus calyciflorus and on its ability to adapt and recover through generations. In our study, Ag-NPs and CuO-NPs inhibited the rotifer population growth rate and caused mortality at low concentrations (< 100 μg L−1). Ag-NPs and CuO-NPs decreased in the medium when organisms were present (48 h exposure: 51.1 % and 66.9 %, respectively), similarly Ag+ and Cu2+ also decreased from medium in presence of the organisms (48 h: 35.2 % and 47.3 %, respectively); although the metal concentrations removed from the medium were higher for nanoparticles than metal ions, metal ions showed higher effects then their respective nanoparticle forms. Rotifer populations exposed for 4 generations to the toxicants were able to recover the population growth rate, but some rotifers showed developmental delay and inability to reproduce even after the removal of the toxicants. Intracellular accumulation of reactive oxygen species as well as plasma membrane damage were found in the rotifers at concentrations corresponding to EC10 (Ag-NPs = 1.7 μg L-1, Ag+ = 4.5 μg L-1, CuO-NPs = 46.9 μg L-1, Cu2+ = 35 μg L-1) of the population growth rate. Our results showed, for the first time, that effects of metal nanoparticles and metal ions on rotifer populations may persist along several generations. This should be taken into account when assessing risks of metal nanoparticles in freshwaters.

Factors shaping community patterns of protists and bacteria on a European scale.

Factors shaping community patterns of microorganisms are controversially discussed. Physical and chemical factors certainly limit the survival of individual taxa and maintenance of diversity. In recent years, a contribution of geographic distance and dispersal barriers to distribution patterns of protists and bacteria has been demonstrated. Organismic interactions such as competition, predation and mutualism further modify community structure and maintenance of distinct taxa. Here, we address the relative importance of these different factors in shaping protists and bacterial communities on a European scale using high-throughput sequencing data obtained from lentic freshwater ecosystems. We show that community patterns of protists are similar to those of bacteria. Our results indicate that cross-domain organismic factors are important variables with a higher influence on protists as compared with bacteria. Abiotic physical and chemical factors also contributed significantly to community patterns. The contribution of these latter factors was higher for bacteria, which may reflect a stronger biogeochemical coupling. The contribution of geographical distance was similar for both microbial groups.

Biological Flora of the British Isles: Crassula helmsii

Abstract This account presents information on all aspects of the biology of Crassula helmsii (Kirk) Cockayne (New Zealand Pygmyweed, Australian Swamp Stonecrop) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history, and conservation. Crassula helmsii is an invasive aquatic macrophyte originating from Australia and New Zealand. The first naturalized population was recorded in Britain in 1956. All British specimens appear to represent a single lineage. DNA analysis indicates that British specimens originate from Australia. Crassula helmsii is capable of growing in a wide range of lentic freshwater and riparian habitats. It may grow as free floating, submerged, emergent or terrestrial forms. Morphology can differ markedly on the same stem. Flowers are produced, but with no known pollinators outside of its native range. Reproduction is thought to be predominantly by asexual methods outside Australia and New Zealand, through stem fragmentation and dispersal. Seed germination outside the native range appears to be very rare and poorly understood. Crassula helmsii has been and still is controlled by active management because of fears that its capacity to produce monocultures will lead to loss of biodiversity in the plant communities it invades. Evidence for species losses due to colonization by C. helmsii is rather anecdotal, although suppression of native biomass through competition has been reported. No consistently effective control procedures have been identified.

Documentation of aquatic birds with relation to feeding habits in a lentic freshwater tank of Karnataka, India

Documentation of aquatic birds with relation to feeding habits in a lentic freshwater tank of Karnataka, India

High frequency data provide new insights into evaluating and modeling nitrogen retention in reservoirs

Freshwater ecosystems including lakes and reservoirs are hot spots for retention of excess nitrogen (N) from anthropogenic sources, providing valuable ecological services for downstream and coastal ecosystems. Despite previous investigations, current quantitative understanding on the influential factors and underlying mechanisms of N retention in lentic freshwater systems is insufficient due to data paucity and limitation of modeling techniques. Our ability to reliably predict N retention for these systems therefore remains uncertain. Emerging high frequency monitoring techniques and well-developed ecosystem modeling shed light on this issue. In the present study, we explored the retention of NO3–N during a five-year period (2013–2017) in both annual and weekly scales in a highly flushed reservoir in Germany. We found that annual-averaged NO3–N retention efficiency could be up to 17% with an overall retention efficiency of ∼4% in such a system characterized by a water residence time (WRT) of ∼4 days. On the weekly scale, the reservoir displayed negative retention in winter (i.e. a source of NO3–N) and high positive retention in summer (i.e. a sink for NO3–N). We further identified the critical role of Chl-a concentration together with the well-recognized effects from WRT in dictating NO3–N retention efficiency, implying the significance of biological processes including phytoplankton dynamics in driving NO3–N retention. Furthermore, our modeling approach showed that an established process-based ecosystem model (PCLake) accounted for 58.0% of the variance in NO3–N retention efficiency, whereas statistical models obtained a lower value (40.5%). This finding exemplified the superior predictive power of process-based models over statistical models whenever ecological processes were at play. Overall, our study highlights the importance of high frequency data in providing new insights into evaluating and modeling N retention in reservoirs.

Altitudinal gradients in Magellanic sub-Antarctic lagoons: the effect of elevation on freshwater macroinvertebrate diversity and distribution

BackgroundThe study of altitudinal gradients provides insights about species diversity, distribution patterns and related drivers. The Magellanic sub-Antarctic ecoregion has a steep elevational gradient, peaking at around 1,000 m a.s.l., and marked changes in temperature and landscape composition can be observed over relatively short distances.MethodsThis study assessed freshwater macroinvertebrate diversity associated with lakes and ponds along the altitudinal gradient of a Magellanic sub-Antarctic watershed.ResultsA monotonic decline in species richness was observed with increasing elevation, with simpler and more even community composition at higher altitude. This pattern differs from the mid-peak trend found in streams of the same watershed. Functional feeding group structure also diminished with increasing elevation.DiscussionThe study provides a descriptive baseline of macroinvertebrate community structure associated with lentic freshwater ecosystems in the Magellanic sub-Antarctic ecoregion, and confirms that elevation has substantial effects on community structure, function and environmental features, even in these relatively low elevation mountain ranges. The harsh environmental conditions of this ecoregion increase freshwater macroinvertebrate development time, as well as decreasing habitat availability and food supply, supporting simple but well adapted communities. In conjunction with previous research, this study provides a watershed-scale platform of information underpinning future long-term research in the region.

An optimised eDNA protocol for detecting fish in lentic and lotic freshwaters using a small water volume.

Environmental DNA is increasingly being used for assessing the presence and relative abundance of fish in freshwater, but existing protocols typically rely on filtering large volumes of water which is not always practical. We compared the effects of water volume, filtration type and eDNA extraction procedures in the detection of fish in three freshwater bodies (pond, lake and river) using a short fragment of the 12s rRNA mtDNA gene. Quantification of eDNA capture efficiency after DNA extraction, as well as amplification efficiency, were evaluated by conventional PCR and quantitative PCR. No significant differences on eDNA capture yield were found among freshwater bodies, but increasing water volume had a positive effect on eDNA capture and amplification efficiency. Although highest eDNA capture rates were obtained using 2 L of filtered water, 100 mL syringe filtration in combination with ethanol- sodium acetate precipitation proved to be more practical and increased quantitative PCR amplification efficiency by 6.4%. Our results indicate that such method may be optimal to detect fish species effectively across both lotic and lentic freshwater environments.

Evaluating improvements to exposure estimates from fate and transport models by incorporating environmental sampling effort and contaminant use

Widespread chemical contamination represents one of the largest threats of the Anthropocene. The Pesticide in Water Calculator (PWC) is a fate and transport model used by the Environmental Protection Agency and Health Canada to estimate pesticide exposures in lentic freshwater ecosystems and make pesticide registration decisions. Here, we show that maximum measured concentrations of 31% of herbicides and 42% of insecticides exceeded maximum estimated environmental concentrations (EECs) produced by the PWC, suggesting that EECs often do not represent worst-case exposure as they have been purported to do. Based on this observation, we generated statistical models using EECs and over 600,000 field measurements of 31 common insecticides and herbicides to document if the congruence of EECs and maximum field measurements could be improved by accounting for environmental sampling effort (number of times a pesticide is sampled) and contaminant application, factors commonly ignored in most fate and transport models. For lentic systems, variance in pesticide field measurements explained by EECs increased by 50% when sampling effort was included. For lotic systems, variance explained increased by only 4%, most likely because lotic systems are sampled over 4.9 times as much as lentic systems. Including use more than doubled the ability of the EECs to predict maximum pesticides concentrations in lentic systems. Our results suggest that exposure characterization in risk assessment can likely be improved by considering sampling effort and use, thus providing more defensible environmental standards and regulations.

Trophic role of marbled crayfish in a lentic freshwater ecosystem

Trophic role of marbled crayfish in a lentic freshwater ecosystem

Feeding inhibition tests as a tool for seston quality evaluation in lentic ecosystems: salinization impact

Environmental disturbance on freshwater ecosystems significantly impacts all levels of the trophic web. Salinity in lentic freshwater ecosystems, as a consequence of climatic changes, is rising concern in the scientific community. These alterations affect water quality, the composition and diversity of the aquatic communities. This study aimed to assess the seston quality of two lentic ecosystems, Crestuma reservoir and lake Vela, and evaluate the effects of salinity on food performance of Daphnia magna and Daphnia longispina (isolated from the referred ecosystems). Feeding inhibition tests were used to conduct these two evaluations. Physical and chemical water classification revealed a poor or good ecological potential of the two lentic ecosystems, according to WFD approach. To evaluate seston quality, filtered and unfiltered water samples from the lentic ecosystems were used as treatments. Although only summer samples from Crestuma presented good water quality, the results from the feeding inhibition tests showed that seston from lake Vela presented more nutritional quality. Concerning the assay to evaluate the salinity effect on Daphnia spp., a significant reduction in the filtration rate was observed. The NOEC value was 0.7 g/L NaCl and 0.8 g/L NaCl for D. magna and D. longispina C and V, respectively. The LOEC value was also distinct between species, being 1.0 g/L and 0.9 g/L, respectively. This work allowed to verify that feeding inhibition tests are not sensitive enough for assess the quality of natural waters. However, these tests are economically viable and have high sensitivity to evaluate NaCl effects on Daphnia spp.

The Predaceous Diving Beetle Fauna (Coleoptera: Dytiscidae) in Highway-Associated Aquatic Habitats in Southern Mississippi, USA

Highway-associated, lentic freshwater habitats are ubiquitous throughout the landscape of the southern USA and support diverse assemblages of aquatic insects. However, because of their generally small size, dynamic hydro-period, and disturbed nature, these habitats are often overlooked by naturalists, and subsequently faunal surveys are rare. This work addressed this knowledge gap by specifically surveying for a common and widespread group of beetles within these habitats, predaceous diving beetles (Coleoptera: Dytiscidae). Semi-permanent and ephemeral freshwater habitats associated with two major state highways and one interstate highway were sampled in early and late summer of 2009 within a 40-km radius of Hattiesburg, MS. Among 15 tire ruts, 18 ditches, and 30 ponds, we collected 861 adult and 545 larval dytiscids representing 18 different species. Our findings suggest that highway-associated, freshwater habitats may act as important habitat and dispersal “stepping-stones” for certain species of dytiscids in the landscape and likely play a part in maintaining the metapopulations and regional biodiversity of these taxa.

Filling ephemeral ponds affects development and phenotypic expression in Ambystoma talpoideum

Abstract Populations and communities are often greatly affected by disturbances and variation in abiotic habitat conditions. Many of these effects are contingent on relatively predictable, yet still variable, environmental conditions that drive the life history strategies and development pathways of organisms in those habitats. However, much focus has been placed on aspects of such changes that cause mortality or movement from patches, whereas a multitude of outcomes can occur in natural systems. In lentic freshwater habitats, hydroperiod is a defining environmental characteristic, with temporary ponds supporting distinct communities of organisms with complex life cycles and plastic developmental trajectories. Little consideration has been given to the effects of refilling of ponds with variable hydroperiods, as lengthening the hydroperiod can extend the time organisms spend in their aquatic stages, allowing for the acquisition of more resources. We hypothesised that increasing the volume of small ponds and adding competitors (Ambystoma maculatum) at the time of filling would interactively affect the development and phenotypic expression of Ambystoma talpoideum. We introduced larval A. talpoideum to experimental mesocosms and manipulated water level (small, low volume mesocosms; filled, full mesocosms) and the addition of competitors (A. maculatum) at the time of filling in a 2 × 2 factorial design. We found that low volume mesocosms were dominated by metamorphs, while filling resulted in a more even mix of metamorphs, larvae and paedomorphs in full mesocosms. Filling resulted in larger metamorphs and paedomorphs, but did not affect larvae, whereas addition of A. maculatum shortened the larval period of metamorphs. We provide evidence that changes in abiotic habitat conditions, such as variation in the volume of ponds, can shift the development and phenotype of organisms. This plasticity may allow species to ensure the success of populations under both improvement and deterioration of environmental conditions. Hence, phenotypes like paedomorphic A. talpoideum can breed sooner than metamorphs, theoretically maximising the fitness of both individuals and populations.

Dry-wet cycles of kettle hole sediments leave a microbial and biogeochemical legacy

Understanding interrelations between an environment's hydrological past and its current biogeochemistry is necessary for the assessment of biogeochemical and microbial responses to changing hydrological conditions. The question how previous dry-wet events determine the contemporary microbial and biogeochemical state is addressed in this study. Therefore, sediments exposed to the atmosphere of areas with a different hydrological past within one kettle hole, i.e. (1) the predominantly inundated pond center, (2) the pond margin frequently desiccated for longer periods and (3) an intermediate zone, were incubated with the same rewetting treatment. Physicochemical and textural characteristics were related to structural microbial parameters regarding carbon and nitrogen turnover, i.e. abundance of bacteria and fungi, denitrifiers (targeted by the nirK und nirS functional genes) and nitrate ammonifiers (targeted by the nrfA functional gene). Our study reveals that, in combination with varying sediment texture, the hydrological history creates distinct microbial habitats with defined boundary conditions within the kettle hole, mainly driven by redox conditions, pH and organic matter (OM) composition. OM mineralization, as indicated by CO2-outgassing, was most efficient in exposed sediments with a less stable hydrological past. The potential for nitrogen retention via nitrate ammonification was highest in the hydrologically rather stable pond center, counteracting nitrogen loss due to denitrification. Therefore, the degree of hydrological stability is an important factor leaving a microbial and biogeochemical legacy, which determines carbon and nitrogen losses from small lentic freshwater systems in the long term run.

Quality parameters of black carp (Mylopharyngodon piceus) raised in lotic and lentic freshwater systems

Compared with lentic freshwater systems, lotic systems support swimming and metabolic activities that improve the quality of fish raised for food. This study evaluated the quality and flavor of black carp (Mylopharyngodon piceus) fish fillets produced by long-term farming in lotic and lentic freshwater systems. Physiochemical variables, flavor characteristics, freshness indicators, and meat texture were compared. Specimens were cooked at 105 °C at normal atmospheric pressure in order to evaluate the fish samples after heating process. The lotic population (LOP) had significantly greater growth, protein content, better textural traits, and lower total fat content compared with the lentic population (LEP). LOP fish were rich in C20:1n-9 fatty acids and total amino acids. LOP were rich in volatile compounds including esters, alcohols, and aldehydes but poor in alkanes and acids. Raw (R)-LEP fish were higher in trimethylamine oxide (TMAO) than R-LOP fish. Cooked (C)-LOP fish were high in TMAO and low in trimethylamine (TMA) compared with C-LEP fish. R-LOP and C-LOP fish were both high in adenosine monophosphate (AMP) compared with R-LEP and C-LEP fish. Inosine (HxR) content was higher in C-LOP than in C-LEP fish. LOP-raised black carp are preferred because of the nutritional value, pleasant flavor, and related health benefits.

Draft Genome Sequence of the Planktic Cyanobacterium Tychonema bourrellyi, Isolated from Alpine Lentic Freshwater.

ABSTRACTWe describe here the draft genome sequence of the cyanobacterium Tychonema bourrellyi, assembled from a metagenome of a nonaxenic culture. The strain (FEM_GT703) was isolated from a freshwater sample taken from Lake Garda, Italy. The draft genome sequence represents the first assembled T. bourrellyi strain.

Relative predation risk and risk of desiccation co-determine oviposition preferences in Cope's gray treefrog, Hyla chrysoscelis.

Habitat permanence and threat of predation are primary drivers of community assembly and composition in lentic freshwater systems. Pond-breeding amphibians select oviposition sites to maximize fitness and minimize risks of predation and desiccation of their offspring, typically facing a trade-off between the two as predation risk often increases as desiccation risk decreases. To experimentally determine if Hyla chrysoscelis partition oviposition along gradients of relative desiccation risk and predation risk, we tested oviposition site preference in a natural population of treefrogs colonizing experimental ponds that varied in water depth and contained predatory larvae of two Ambystoma salamander species. Hyla chrysoscelis selected habitats with both lower predation risk, avoiding A. talpoideum over A. maculatum, and lower desiccation risk, selecting ponds with three times greater depth. We demonstrate that adult oviposition site choices simultaneously minimize relative predation risk and desiccation risk and that closely related salamander species produce functionally different responses among colonizing animals.

Context-dependent resistance of freshwater invertebrate communities to drying.

More freshwater ecosystems are drying in response to global change thereby posing serious threat to freshwater biota and functions. The production of desiccation‐resistant forms is an important adaptation that helps maintain biodiversity in temporary freshwaters by buffering communities from drying, but its potential to mitigate the negative effects of drying in freshwater ecosystems could vary greatly across regions and ecosystem types. We explored this context dependency by quantifying the potential contribution of desiccation‐resistance forms to invertebrate community recovery across levels of regional drying prevalence (defined as the occurrence of drying events in freshwaters in a given region) and ecosystem types (lentic, lotic) in temporary neotropical freshwaters. We first predicted that regional drying prevalence influences the selection of species with desiccation‐resistant forms from the regional species pools and thus increases the ability of communities to recover from drying. Second, we predicted lentic freshwaters harbor higher proportions of species with desiccation‐resistant forms compared to lotic, in response to contrasted hydrologic connectivity. To test these predictions, we used natural experiments to quantify the contribution of desiccation‐resistant forms to benthic invertebrate community recovery in nine intermittent streams and six geographically isolated temporary wetlands from three Bolivian regions differing in drying prevalence. The contribution of desiccation‐resistant forms to community recovery was highest where regional drying prevalence was high, suggesting the species pool was adapted to regional disturbance regimes. The contribution of desiccation‐resistant forms to community recovery was lower in streams than in wetlands, emphasizing the importance of hydrologic connectivity and associated recolonization processes from in‐stream refuges to recovery in lotic systems. In all regions, the majority of functional traits were present in desiccation‐resistant taxa indicating this adaptation may help maintain ecosystem functions by buffering communities from the loss of functional traits. Accounting for regional context and hydrologic connectivity in community recovery processes following drying can help refine predictions of freshwater biodiversity response to global change.