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At least 739 records · Page 41Linked to original sources
USGS2021

Twenty-five essential research questions to inform the protection and restoration of freshwater biodiversity

Freshwater biodiversity is declining at an unprecedented rate. Freshwater conservationists and environmental managers have enough evidence to demonstrate that action must not be delayed but have insufficient evidence to identify those actions that will be most effective in reversing the current trend. Here, the focus is on identifying essential research topics that, if addressed, will contribute directly to restoring freshwater biodiversity through supporting ‘bending the curve’ actions (i.e. those actions leading to the recovery of freshwater biodiversity, not simply deceleration of the current downward trend). The global freshwater research and management community was asked to identify unanswered research questions that could address knowledge gaps and barriers associated with ‘bending the curve’ actions. The resulting list was refined into six themes and 25 questions. Although context-dependent and potentially limited in global reach, six overarching themes were identified: (i) learning from successes and failures; (ii) improving current practices; (iii) balancing resource needs; (iv) rethinking built environments; (v) reforming policy and investments; and (vi) enabling transformative change. Bold, efficient, science-based actions are necessary to reverse biodiversity loss. We believe that conservation actions will be most effective when supported by sound evidence, and that research and action must complement one another. These questions are intended to guide global freshwater researchers and conservation practitioners, identify key projects and signal research needs to funders and governments. Our questions can act as springboards for multidisciplinary and multisectoral collaborations that will improve the management and restoration of freshwater biodiversity.

Aquatic Conservation: Marine and Freshwater Ecosys↗
USGS2020

Scaling responses of leaf nutrient stoichiometry to the lakeshore flooding duration gradient across different organizational levels

Most wetlands have been subject to changes in flooding regimes by climate change and human activities, resulting in widespread alteration of wetland plants at different organizational levels. However, scaling the responses of wetland plants to changes in flooding regimes is still challenging, because flooding could indirectly affect wetland plants through affecting environment factors (e.g. soil properties). During the non-flooding period, we investigated leaf N and P stoichiometry at three organizational levels (intra-species, inter-species, inter-community) along a flooding duration gradient in a lakeshore meadow of Poyang Lake floodplain, China. At the intra-species level, leaf N and P stoichiometry showed species-specific responses to flooding duration. At the inter-species level, leaf N or P contents or N:P ratio showed no significant response to flooding duration. At the inter-community level, leaf N and P contents significantly increased with flooding duration, while leaf N:P ratio decreased. At each organizational level, leaf N and P stoichiometry showed poor correlation with soil N and P stoichiometry. Moreover, intra-specific responses of leaf N and P contents to flooding duration and soil nutrient content increased with mean flooding duration of species distribution, which was the index of species hydrological niche. Intraspecific variation had lower contribution than species turnover to variations in community leaf nutrient stoichiometry. In all, flooding duration affected leaf N and P stoichiometry mainly through direct pathway at the intra-species and inter-community level, rather than the indirect pathway via soil nutrient stoichiometry. Therefore, our results have implications for scaling up from environmental conditions to ecosystem processes via wetland plant communities.

Science of the Total Environment↗
USGS2025

Interrogating process deficiencies in large-scale hydrologic models with interpretable machine learning

Large-scale hydrologic models are increasingly being developed for operational use in the forecasting and planning of water resources. However, the predictive strength of such models depends on how well they resolve various functions of catchment hydrology, which are influenced by gradients in climate, topography, soils, and land use. Most assessments of hydrologic model uncertainty have been limited to traditional statistical methods. Here, we present a proof-of-concept approach that uses interpretable machine learning techniques to provide post hoc assessment of model sensitivity and process deficiency in hydrologic models. We train a random forest model to predict the Kling–Gupta efficiency (KGE) of National Water Model (NWM) and National Hydrologic Model (NHM) streamflow predictions for 4383 stream gauges in the conterminous United States. Thereafter, we explain the local and global controls that 48 catchment attributes exert on KGE prediction using interpretable Shapley values. Overall, we find that soil water content is the most impactful feature controlling successful model performance, suggesting that soil water storage is difficult for hydrologic models to resolve, particularly for arid locations. We identify nonlinear thresholds beyond which predictive performance decreases for NWM and NHM. For example, soil water content less than 210 mm, precipitation less than 900 mm yr −1 , road density greater than 5 km km −2 , and lake area percent greater than 10 % contributed to lower KGE values. These results suggest that improvements in how these influential processes are represented could result in the largest increases in NWM and NHM predictive performance. This study demonstrates the utility of interrogating process-based models using data-driven techniques, which has broad applicability and potential for improving the next generation of large-scale hydrologic models.

conterminous United States↗
USGS2025

Science support for recovery of Southwestern Willow Flycatcher (Empidonax traillii extimus) on conserved lands in San Diego County

This document was developed based on the results of scientific research to support management and recovery of the endangered Southwestern Willow Flycatcher ( Empidonax traillii extimus ) and its habitat in San Diego County, California. A migratory species restricted to riparian habitat for breeding, the flycatcher is present in southern California from May to August. The flycatcher has declined over the last several decades primarily in response to habitat loss, and possibly Brown-headed Cowbird ( Molothrus ater ) parasitism. This document compiles and analyzes data collected by USGS scientists on population size, distribution, demography, and breeding habitat condition and uses this information to evaluate potential management options and locations relative to several variables including spatial proximity to currently occupied locations, historical occupation, and potential for restoration that would benefit the flycatcher and expand populations. Location-specific management options and habitat restoration opportunities are ranked based on the contribution of each location to promoting regional flycatcher persistence. The results of these analyses can be used by land and resource managers to develop their habitat management projects and priorities and promote flycatcher recovery.

California↗
USGS1990

Radium and radon in Charlotte Harbor Estuary, Florida

Radium-226 and 222 Rn activities are greater in the estuarine waters of northern Charlotte Harbor and the lower tidal Peace and Myakka Rivers, Florida, than in either the freshwater reaches of the rivers or waters of the lower estuary and the Gulf of Mexico. The activity of 226 Ra in the tidal rivers increases with decreasing river inflow, with a maximum value of 548 dpm 1001 −1 measured in the tidal Myakka River. The source of the high activity of 226 Ra and 222 Rn is predominantly ground water inflow. Because of the large ground water input, the contribution of 226 Ra from suspended and bottom sediments is a smaller fraction of the total 226 Ra input than in many other estuaries. Although ground water 226 Ra activity in the area varies widely, we estimate that artesian ground water inflow to the tidal rivers is similar in magnitude to the flow of the rivers above the tidal reach during the dry season.

Florida↗
USGS2019

Methane emissions from artificial waterbodies dominate the carbon footprint of irrigation: A study of transitions in the food-energy-water-climate nexus (Spain, 1900-2014)

Irrigation in the Mediterranean region has been used for millennia and has greatly expanded with industrialization. Irrigation is critical for climate change adaptation, but it is also an important source of greenhouse gas emissions. This study analyzes the carbon (C) footprint of irrigation in Spain, covering the complete historical process of mechanization. A 21-fold total, 6-fold area-based, and 4-fold product-based increase in the carbon footprint was observed during the 20th century, despite an increase in water use efficiency. CH 4 emissions from waterbodies, which had not previously been considered in the C footprint of irrigation systems, dominated the emission budget during most of the analyzed period. Technologies to save water and tap new water resources greatly increased energy and infrastructure demand, while improvements in power generation efficiency had a limited influence on irrigation emissions. Electricity production from irrigation dams may contribute to climate change mitigation, but the amount produced in relation to that consumed in irrigation has greatly declined. High uncertainty in CH 4 emission estimates from waterbodies stresses a need for more spatially resolved data and an improved empirical knowledge of the links between water quality, water level fluctuations, and emissions at the regional scale.

Environmental Science & Technology↗
USGS2017

Nearly 400 million people are at higher risk of schistosomiasis because dams block the migration of snail-eating river prawns

Dams have long been associated with elevated burdens of human schistosomiasis, but how dams increase disease is not always clear, in part because dams have many ecological and socio-economic effects. A recent hypothesis argues that dams block reproduction of the migratory river prawns that eat the snail hosts of schistosomiasis. In the Senegal River Basin, there is evidence that prawn populations declined and schistosomiasis increased after completion of the Diama Dam. Restoring prawns to a water-access site upstream of the dam reduced snail density and reinfection rates in people. However, whether a similar cascade of effects (from dams to prawns to snails to human schistosomiasis) occurs elsewhere is unknown. Here, we examine large dams worldwide and identify where their catchments intersect with endemic schistosomiasis and the historical habitat ranges of large, migratory Macrobrachium spp. prawns. River prawn habitats are widespread, and we estimate that 277–385 million people live within schistosomiasis-endemic regions where river prawns are or were present (out of the 800 million people who are at risk of schistosomiasis). Using a published repository of schistosomiasis studies in sub-Saharan Africa, we compared infection before and after the construction of 14 large dams for people living in: (i) upstream catchments within historical habitats of native prawns, (ii) comparable undammed watersheds, and (iii) dammed catchments beyond the historical reach of migratory prawns. Damming was followed by greater increases in schistosomiasis within prawn habitats than outside prawn habitats. We estimate that one third to one half of the global population-at-risk of schistosomiasis could benefit from restoration of native prawns. Because dams block prawn migrations, our results suggest that prawn extirpation contributes to the sharp increase of schistosomiasis after damming, and points to prawn restoration as an ecological solution for reducing human disease.

Philosophical Transactions of the Royal Society B:↗
USGS2007

Glaciers dominate eustatic sea-level rise in the 21st century

Ice loss to the sea currently accounts for virtually all of the sea-level rise that is not attributable to ocean warming, and about 60% of the ice loss is from glaciers and ice caps rather than from the two ice sheets. The contribution of these smaller glaciers has accelerated over the past decade, in part due to marked thinning and retreat of marine-terminating glaciers associated with a dynamic instability that is generally not considered in mass-balance and climate modeling. This acceleration of glacier melt may cause 0.1 to 0.25 meter of additional sea-level rise by 2100.

Science↗
USGS2020

Spectral wave-driven bedload transport across a coral reef flat/lagoon complex

Coral reefs are an important source of sediment for reef-lined coasts by helping to maintain beaches while also providing protection in the form of wave energy dissipation. Understanding the mechanisms by which sediment is delivered to the coast as well as better constraining the total volumes generated are critical for projecting future coastal change. A month-long hydrodynamics and sediment transport study on a fringing reef/lagoon complex in Western Australia indicates that lower frequency constituents of wave energy are important to the total bedload transport of sediment across the reef flat and lagoon to the shoreline. The reef flat and the lagoon are characterized by distinctly different transport regimes, resulting in an offset in the timing of bedform migration between the two. Short-term storage of sediment is noted on the reef flat, which is subsequently washed out into the lagoon when offshore wave heights increase and strong currents due to wave breaking at the reef crest develop. This sudden influx of sediment is a significant control on bedform migration rates in the lagoon. Infragravity wave energy on the reef flat and lagoon make an important contribution to the migration of bedforms and resultant bedload transport. Given the complexity of the hydrodynamics of fringing reefs, the transfer of energy to lower frequency bands, as well as accurate estimates of sources and sinks of sediment, must but considered in order to correctly model the transport of sediment from the reef to the coast.

Ningaloo Reef↗
USGS2008

Origins of sediment-associated contaminants to the Marais Vernier, the Seine Estuary, France

The Marais Vernier is the largest freshwater wetland in the Seine Estuary in northern France. It is in a heavily urbanized and industrialized region and could be affected by atmospheric deposition and by fluvial input of contaminants in water diverted from the Seine River. To evaluate contaminant histories in the wetland and the region, sediment cores were collected from two open-water ponds in the Marais Vernier: the Grand-Mare, which was connected to the Seine by a canal from 1950 to 1996, and the Petite Mare, which has a small rural watershed. Diversions from the Seine to the Grand-Mare increased sedimentation rates but mostly resulted in low contaminant concentrations and loading rates, indicating that the sediment from the Seine was predominantly brought upstream by tidal currents from the estuary and was not from the watershed. Atmospheric sources of metals dominate inputs to the Petite Mare; however, runoff of metals from vehicle-related sources in the watershed might contribute to the upward trends in concentrations of Cr, Cu, and Zn. Estimates of atmospheric deposition using the Petite Mare core are consistent with measured deposition in the region and are mixed (similar for Hg and Pb; larger for Cd, Cu, and Zn) compared with deposition estimated from sediment cores in the northeastern United States. A local source of PAHs in the watershed of the Petite Mare is indicated by higher concentrations, higher accumulation rates, and a different, more petrogenic, PAH assemblage than in the Grand-Mare. The study illustrates how diverse sources and transport pathways can affect wetlands in industrial regions and can be evaluated using sediment cores from the wetland ponds. ?? 2008 Springer Science+Business Media B.V.

Water, Air, & Soil Pollution↗
USGS2006

Influence of potentially confounding factors on sea urchin porewater toxicity tests

The influence of potentially confounding factors has been identified as a concern for interpreting sea urchin porewater toxicity test data. The results from >40 sediment-quality assessment surveys using early-life stages of the sea urchin Arbacia punctulata were compiled and examined to determine acceptable ranges of natural variables such as pH, ammonia, and dissolved organic carbon on the fertilization and embryological development endpoints. In addition, laboratory experiments were also conducted with A. punctulata and compared with information from the literature. Pore water with pH as low as 6.9 is an unlikely contributor to toxicity for the fertilization and embryological development tests with A. punctulata. Other species of sea urchin have narrower pH tolerance ranges. Ammonia is rarely a contributing factor in pore water toxicity tests using the fertilization endpoint, but the embryological development endpoint may be influenced by ammonia concentrations commonly found in porewater samples. Therefore, ammonia needs to be considered when interpreting results for the embryological development test. Humic acid does not affect sea urchin fertilization at saturation concentrations, but it could have an effect on the embryological development endpoint at near-saturation concentrations. There was no correlation between sediment total organic carbon concentrations and porewater dissolved organic carbon concentrations. Because of the potential for many varying substances to activate parthenogenesis in sea urchin eggs, it is recommended that a no-sperm control be included with every fertilization test treatment. ?? 2006 Springer Science+Business Media, Inc.

Archives of Environmental Contamination and Toxico↗
USGS2009

Toxicity of atmospheric aerosols on marine phytoplankton

Atmospheric aerosol deposition is an important source of nutrients and trace metals to the open ocean that can enhance ocean productivity and carbon sequestration and thus influence atmospheric carbon dioxide concentrations and climate. Using aerosol samples from different back trajectories in incubation experiments with natural communities, we demonstrate that the response of phytoplankton growth to aerosol additions depends on specific components in aerosols and differs across phytoplankton species. Aerosol additions enhanced growth by releasing nitrogen and phosphorus, but not all aerosols stimulated growth. Toxic effects were observed with some aerosols, where the toxicity affected picoeukaryotes and Synechococcus but not Prochlorococcus.We suggest that the toxicity could be due to high copper concentrations in these aerosols and support this by laboratory copper toxicity tests preformed with Synechococcus cultures. However, it is possible that other elements present in the aerosols or unknown synergistic effects between these elements could have also contributed to the toxic effect. Anthropogenic emissions are increasing atmospheric copper deposition sharply, and based on coupled atmosphere-ocean calculations, we show that this deposition can potentially alter patterns of marine primary production and community structure in high aerosol, low chlorophyll areas, particularly in the Bay of Bengal and downwind of South and East Asia.

Proceedings of the National Academy of Sciences of↗
USGS2017

Biocrust ecology: Unifying micro- and macro-scales to confront global change

Biological soil crusts (biocrusts) are communities of microbes, lichens and bryophytes living at the soil surface in drylands (Fig. 1; Belnap et al ., 2016). Biocrusts occur on all continents and can comprise a majority of cover in some systems (Belnap et al ., 2016). While species diversity and distributions have long been a research focus, interest in controls on community composition and cover has expanded as biocrusts are increasingly recognized for their roles in ecosystem functioning (Deane-Coe and Stanton, 2017). For example, biocrust organisms can stabilize soils (Belnap et al ., 2016; Faist et al ., 2017), fix atmospheric carbon (C) (Sancho et al ., 2016), and serve as the foremost source of ‘new’ soil nitrogen (N) in drylands, via N 2 fixation (Barger et al ., 2016) These contributions to gross primary production and soil fertility could be quite large, as high-end estimates suggest biocrusts and similar communities of bryophytes and lichens might account for 10% of terrestrial C- and 50% of N-fixation globally (Elbert et al ., 2012). Yet verifying these and other biocrust roles in ecosystem functioning is complicated by limited knowledge of biocrust cover and composition across the vast dryland biome (Ferrenberg et al ., 2017). It was against this backdrop that ‘Biocrust3: the 3 rd International workshop on biological soil crusts’ was held in Moab, UT, USA, on 26-30 September 2016. The workshop brought together over 50 scientists from 21 countries and six continents, and included numerous biocrust science pioneers (Fig. 2). The meeting was notable for its cross-scale focus, discussion of novel molecular and imaging techniques, and sessions on mapping and restoring biocrusts in a changing world. Here, we synthesize a central theme that emerged from Biocrust3, namely the potential for combining cutting edge tools with studies focused on organismal traits, ecosystem functions, and global change biology to advance the frontier of biocrust ecology.

New Phytologist↗
USGS2021

The role of surges during periods of very shallow water on sediment transport over tidal flats

Periods of very shallow water (water depth in the order of 10 cm) occur daily on tidal flats because of the propagation of tides over very gently sloping beds, leading to distinct morphodynamical phenomena. To improve the understanding of the characteristics of velocity and suspended sediment concentration (SSC) surges and their contribution to sediment transport and local bed changes during periods of very shallow water, measurements of near-bed flow, and SSC were carried out at two cross-shore locations on an intertidal flat along the Jiangsu coast, China. Furthermore, the role of surges in local resuspension and morphological change was explored. Results indicate that flow and SSC surges occurred at both stations during very shallow water periods. On the lower intertidal flat, flood surges were erosive, while weaker surges on the middle intertidal flat were not. Surges on lower intertidal flats resulted in local resuspension and strong turbidity, contributing up to 25% of the onshore-suspended sediment flux during flood tides, even though they last only 10% of the flood duration. When surges travel across the flats, conditions change from erosional to depositional. Velocity surges on the middle intertidal flat were too weak to resuspend bed sediment, and the associated SSC surges were produced by advection.

Jiangsu Coast↗
USGS1967

Infection of the walleye, Stizostedion v. vitreum, of western Lake Erie with Bothriocephalus cuspidatus (Cooper)

In recent years appreciable changes have taken place in the biota and physiochemical conditions in Lake Erie. The accelerated eutrophication of the lake has been accompanied by the near disappearance of several fish species, e.g., blue pike (Stizostedion vitreum glaucum), lake herring (Coregonus artedi), lake trout (Salvelinus namaycush), sauger (Stizostedion canadense), and whitefish (Coregonus clupeaformis). Interest in the biology of the remaining species has increased as means have been sought to preserve their numbers in the lake. This report, which describes the caecal and intestinal parasites of the walleye, Stizostedion vitreum vitreum, is a contribution to the natural history of this fish in western Lake Erie. This study concerns: the type and degree of intestinal parasitic infestations in a single year class of walleyes during their first 3 years of life; seasonal changes in the incidence and maturity of the dominant parasite Bothriocephalus cuspidatus; and the effects of the infestations on the physical condition of the host.

Papers of the Michigan Academy of Science, Arts, a↗
USGS2026

Mechanisms of Devils Lake’s responses to recent climatic wetting: Insights from a physically based hydrologic model

Study region Devils Lake Basin of the Northern Great Plains (NGP) region, North Dakota, USA Study focus Understanding the mechanism of Devils Lake’s responses and basin-wide hydrologic change under a wet-climatic regime using a process-based and cold region hydrologic model. New hydrologic insights Model results illustrate that three distinct hydroclimatic periods occurred during the study: Water Years 2002–05, 2006–11, and 2012–18. Following a brief time of contraction and growth, the latter two periods provide a complete picture of a wetting to drying cycle during an overall wetting regime. From 2006–2011, Devils Lake (DL) grew primarily due to lateral inflow, driven by strong precipitation and high frozen soil content leading up to the 2011 floods. In addition, during wet years, the snowmelt streamflow from the eastern and central parts of the DL Basin contributes significantly to lake growth compared to the western part. By contrast, from 2012 to 18, DL entered a contraction period, dominated by evaporation losses and anthropogenic flood control operations. Contributors to upstream drying included low precipitation, minimal snowpack accumulation, slightly lower frozen soil ratios, and minimal snowmelt runoff.

North Dakota↗
USGS2015

Megathrust earthquakes and sea-level change: A tribute to George Plafker

For numerous scientific disciplines that contribute to the understanding of megathrust earthquakes, 2014 was an anniversary year of two great, >M w 9, earthquakes; fifty years since the March 27 1964 earthquake in Alaska and ten years since the December 26 2004 Aceh-Andaman earthquake and attendant tsunami. 2014 was also the final year of International Geoscience Programme (IGCP) Project 588 “Preparing for Coastal Change”, which was the latest in the 25 year history of IGCP coastal change research.

Quaternary Science Reviews↗
USGS2026

Importance of fish in the diet of Adélie penguins across multiple life stages

Over recent decades, the Adélie penguin ( Pygoscelis adeliae ) population has grown across most of its range, the exception being the northern coast of the western Antarctic Peninsula (WAP). In the Ross Sea, the very large Cape Crozier colony grew to reach ~9% of the global population. Demographic factors driving the Cape Crozier trend have yet to be identified. However, low chick fledging mass - a negative influence in the northern WAP where the diet is mostly less-energy-dense krill - is not showing an effect in the Cape Crozier colony. Previously, we hypothesized that Cape Crozier fledglings, and post-breeding adults, must be finding sufficient higher-quality prey once free of the prey-depleted colony foraging area, with subsequent higher survival. Here we explore penguin diet within and outside the colony foraging area using stable isotope analysis (SIA) of feathers: those grown by post-breeding adults outside the foraging area, prior to moult, compared to those of near-fledged chicks raised on meals obtained within the foraging area. Second, we explore whether a major difference occurs between breeding and post-breeding diet of adults from a small, nearby colony (Cape Royds) that exploits a smaller, little-depleted preyscape. Finally, we compare the results to SIA analyses published by others to explore whether the pre-moult diet of Ross Island adults, mostly foraging within the north-eastern Ross Sea, compares with that of adults nesting in the southern WAP (Bellingshausen Sea coast). At the latter, populations are not decreasing, with diet containing an appreciable contribution of fish. The results confirmed that fish contributed greatly to chick diets at both Ross Island colonies (δ 15 N 10.6–11.4). Once adults were released from central-place foraging, SIA levels (δ 15 N 9.7–12.9) were similar to those of the southern WAP. Foraging on energy-dense fish in coastal Antarctic waters could be one reason Adélie penguins are among the most abundant and therefore most ecologically successful penguin species.

Antarctic Science↗