A functional definition to distinguish ponds from lakes and wetlands

Ponds are often identified by their small size and shallow depths, but the lack of a universal evidence-based definition hampers science and weakens legal protection. Here, we compile existing pond definitions, compare ecosystem metrics (e.g., metabolism, nutrient concentrations, and gas fluxes) among ponds, wetlands, and lakes, and propose an evidence-based pond definition. Compiled definitions often mentioned surface area and depth, but were largely qualitative and variable. Government legislation rarely defined ponds, despite commonly using the term. Ponds, as defined in published studies, varied in origin and hydroperiod and were often distinct from lakes and wetlands in water chemistry. We also compared how ecosystem metrics related to three variables often seen in waterbody definitions: waterbody size, maximum depth, and emergent vegetation cover. Most ecosystem metrics (e.g., water chemistry, gas fluxes, and metabolism) exhibited nonlinear relationships with these variables, with average threshold changes at 3.7 ± 1.8 ha (median: 1.5 ha) in surface area, 5.8 ± 2.5 m (median: 5.2 m) in depth, and 13.4 ± 6.3% (median: 8.2%) emergent vegetation cover. We use this evidence and prior definitions to define ponds as waterbodies that are small (< 5 ha), shallow (< 5 m), with < 30% emergent vegetation and we highlight areas for further study near these boundaries. This definition will inform the science, policy, and management of globally abundant and ecologically significant pond ecosystems.Fil: Richardson, David C.. State University of New York at New Paltz; Estados UnidosFil: Holgerson, Meredith A.. Cornell University; Estados UnidosFil: Farragher, Matthew J.. University of Maine; Estados UnidosFil: Hoffman, Kathryn K.. No especifíca;Fil: King, Katelyn B. S.. Michigan State University; Estados UnidosFil: Alfonso, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Andersen, Mikkel R.. No especifíca;Fil: Cheruveil, Kendra Spence. Michigan State University; Estados UnidosFil: Coleman, Kristen A.. University of York; Reino UnidoFil: Farruggia, Mary Jade. University of California at Davis; Estados UnidosFil: Fernandez, Rocio Luz. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hondula, Kelly L.. No especifíca;Fil: López Moreira Mazacotte, Gregorio A.. Leibniz - Institute of Freshwater Ecology and Inland Fisheries; AlemaniaFil: Paul, Katherine. No especifíca;Fil: Peierls, Benjamin L.. No especifíca;Fil: Rabaey, Joseph S.. University of Minnesota; Estados UnidosFil: Sadro, Steven. University of California at Davis; Estados UnidosFil: Sánchez, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Smyth, Robyn L.. No especifíca;Fil: Sweetman, Jon N.. State University of Pennsylvania; Estados Unido

Spatial and temporal variability in summertime dissolved carbon dioxide and methane in temperate ponds and shallow lakes

Small waterbodies have potentially high greenhouse gas emissions relative to their small footprint on the landscape, although there is high uncertainty in model estimates. Scaling their carbon dioxide (CO2) and methane (CH4) exchange with the atmosphere remains challenging due to an incomplete understanding and characterization of spatial and temporal variability in CO2 and CH4. Here, we measured partial pressures of CO2 (pCO2) and CH4 (pCH4) across 30 ponds and shallow lakes during summer in temperate regions of Europe and North America. We sampled each waterbody in three locations at three times during the growing season, and tested which physical, chemical, and biological characteristics related to the means and variability of pCO2 and pCH4 in space and time. Summer means of pCO2 and pCH4 were inversely related to waterbody size and positively related to floating vegetative cover; pCO2 was also positively related to dissolved phosphorus. Temporal variability in partial pressure in both gases weas greater than spatial variability. Although sampling on a single date was likely to misestimate mean seasonal pCO2 by up to 26%, mean seasonal pCH4 could be misestimated by up to 64.5%. Shallower systems displayed the most temporal variability in pCH4 and waterbodies with more vegetation cover had lower temporal variability. Inland waters remain one of the most uncertain components of the global carbon budget; understanding spatial and temporal variability will ultimately help us to constrain our estimates and inform research priorities

Substantial overnight reaeration by convective cooling discovered in pond ecosystems

Trends in freshwater dissolved oxygen (DO) reflect whole-ecosystem properties and influence organismal survival and behavior. Here we show that small ponds have unique oxygen dynamics that differ from larger lakes. We discovered that ponds undersaturated in DO experienced substantial increases in oxygen concentration overnight. Nighttime increases in DO occurred on 45% of the nights sampled and resulted in DO saturation increasing 12-fold (22% saturation) on average. Oxygen spikes were likely to occur when ponds became at least 1.8°C warmer than the air and later in the season when oxygen levels were low (<31% saturation) and the air was warm (≥5.8°C). We demonstrate that overnight increases in surface water DO resulted from atmospheric oxygen invasion as opposed to internal production. Convective cooling enhanced turbulence and air-water gas exchange, leading to intense bursts of oxygen invasion during nighttime hours. This mechanism has not been demonstrated before and has important implications for the biogeochemistry of these systems, as well as understanding how organisms survive in hypoxic small ponds

A Long-term Demographic Study of a Spotted Salamander (Ambystoma maculatum) Population in Central Ohio

Homan, Rebecca N., Holgerson, Meredith A., Biga, And Lindsay M. (2003): A Long-term Demographic Study of a Spotted Salamander (Ambŋstoma maculatum) Population in Central Ohio. Herpetologica 74, No. 2: 109-116, DOI: 10.1655/herpetologica-d-17-00067.

Freshwater floodplain habitats buffer native food webs from negative effects of nonnative centrarchids and bullfrogs

Species introductions are common in freshwater environments and have the potential to transform community and ecosystem structure. Predatory centrarchid fishes and American Bullfrogs (Lithobates catesbeianus Shaw, 1802 previously Rana catesbeiana) are both widespread aquatic invaders implicated in native amphibian declines. In lowland ecosystems, co-occurrence between native and nonnative amphibian and fish taxa is common; however, the mechanisms that facilitate their co-occurrence are poorly studied. Stable isotope analysis offers a tool to examine trophic interactions among native and nonnative taxa, including predation, competition, and shifting food resource availability, which may provide mechanistic insight into the drivers of co-occurrence. In this study, we used stable isotopes (δ13C and δ15N) to determine how the trophic structure of native fishes and amphibians differs between waterbodies with and without nonnative centrarchid fishes and bullfrogs across a floodplain in southwestern Washington, USA. We hypothesized that native species alter their feeding strategies to reduce niche overlap with nonnative taxa. In the presence of nonnative taxa, Three-spine Stickleback (Gasterosteus aculeatus Linnaeus, 1758), all native larval salamander species (Ambystoma gracile Baird, 1859 and Ambystoma macrodactylum Baird, 1850), and 1 of 2 native larval frog species (Rana aurora Baird and Girard, 1852) exhibited shifts in food resources or trophic position. Despite trophic differences, only 1 species (A. macrodactylum) had a smaller niche size in the presence of nonnatives. The observed trophic shifts reflect changes in habitat or food resources, which may reduce competition or predation and promote co-occurrence between nonnative and native taxa. Our results suggest that the co-occurrence of native and nonnative amphibians and fishes in lowland floodplain habitats may be facilitated by a broad range of food resources and complex habitat structure

Suburbanization Alters Small Pond Ecosystems: Shifts in Nitrogen and Food Web Dynamics

Small ponds often survive the transition from forested to suburban land cover and provide habitat for many species, yet little is known about how suburbanization affects pond ecosystems. We surveyed 18 small ponds across a forest-to-suburban land cover gradient and compared how physical and chemical changes altered biological and ecosystem properties, such as nutrient and food web dynamics. Suburbanization decreased canopy cover, increased water temperatures, and increased periphyton chlorophyll a, but was associated with only weak increases in total nutrients. Yet, stable isotope analysis indicated that suburbanization altered nitrogen dynamics and resource use in the food web. We observed increases in delta N-15 in algae, biofilm, and frog larvae across the suburban gradient, indicative of wastewater intrusion. Suburbanization also shifted the energy and nutrient source of a dominant consumer (Rana sylvatica; = Lithobates sylvaticus) from leaf litter to algae. Overall, we identified cryptic changes to suburban pond ecosystems, highlighting that suburbanization can profoundly impact nutrients and food web resources. As residential land use increases globally, we may expect substantial shifts in nutrient dynamics and food web pathways

Floodplains Provide Important Amphibian Habitat Despite Multiple Ecological Threats

Floodplain ponds and wetlands are productive and biodiverse ecosystems, yet they face multiple threats including altered hydrology, land use change, and non-native species. Protecting and restoring important floodplain ecosystems requires understanding how organisms use these habitats and respond to altered environmental conditions. We developed Bayesian models to evaluate occupancy of six amphibian species across 103 off-channel aquatic habitats in the Chehalis River floodplain, Washington State, USA. The basin has been altered by changes in land use, reduced river–wetland connections, and the establishment of non-native American bullfrogs (Rana catesbeiana = Lithobates catesbeianus) and centrarchid fishes, all of which we hypothesized could influence native amphibian occupancy. Despite potential threats, the floodplain habitats had relatively high rates of native amphibian occupancy, particularly when compared to studies from non-floodplain habitats within the species’ native ranges. The biggest challenge for native amphibians appears to be non-native centrarchid fishes, which strongly reduced occupancy of two native amphibians: the northern red-legged frog (Rana aurora) and the northwestern salamander (Ambystoma gracile). Emergent vegetative cover increased occupancy probability for all five native amphibian species, indicating that plant management may offer a strategy to counter the negative effect of centrarchids by providing refuge from predation. We found that temporary and permanent hydroperiod sites supported different species; hence, both should be conserved on the landscape. Lastly, human-created and natural ponds had similar amphibian occupancy patterns, suggesting that pond construction offers a viable strategy for adding habitats to the floodplain landscape. Overall, floodplain ponds and wetlands provide important amphibian habitat, and we offer management strategies that will bolster amphibian occupancy in an altered floodplain landscape

Holgerson_Ecosphere_Dataset

This dataset represents naive detection of six amphibian species from ponds and wetlands within the Chehalis River Basin, Washington State, USA. In addition to amphibian observations, the dataset includes environmental covariates, such as fish presence, forested land use, emergent vegetation, and day of year

Half of global methane emissions come from highly variable aquatic ecosystem sources

Atmospheric methane is a potent greenhouse gas that plays a major role in controlling the Earth’s climate. The causes of the renewed increase of methane concentration since 2007 are uncertain given the multiple sources and complex biogeochemistry. Here, we present a metadata analysis of methane fluxes from all major natural, impacted and human-made aquatic ecosystems. Our revised bottom-up global aquatic methane emissions combine diffusive, ebullitive and/or plant-mediated fluxes from 15 aquatic ecosystems. We emphasize the high variability of methane fluxes within and between aquatic ecosystems and a positively skewed distribution of empirical data, making global estimates sensitive to statistical assumptions and sampling design. We find aquatic ecosystems contribute (median) 41% or (mean) 53% of total global methane emissions from anthropogenic and natural sources. We show that methane emissions increase from natural to impacted aquatic ecosystems and from coastal to freshwater ecosystems. We argue that aquatic emissions will probably increase due to urbanization, eutrophication and positive climate feedbacks and suggest changes in land-use management as potential mitigation strategies to reduce aquatic methane emissions