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At least 1,477 records · Page 82Linked to original sources
USGS2015

Integrating gene transcription-based biomarkers to understand desert tortoise and ecosystem health

Tortoises are susceptible to a wide variety of environmental stressors, and the influence of human disturbances on health and survival of tortoises is difficult to detect. As an addition to current diagnostic methods for desert tortoises, we have developed the first leukocyte gene transcription biomarker panel for the desert tortoise ( Gopherus agassizii ), enhancing the ability to identify specific environmental conditions potentially linked to declining animal health. Blood leukocyte transcript profiles have the potential to identify physiologically stressed animals in lieu of clinical signs. For desert tortoises, the gene transcript profile included a combination of immune or detoxification response genes with the potential to be modified by biological or physical injury and consequently provide information on the type and magnitude of stressors present in the animal’s habitat. Blood from 64 wild adult tortoises at three sites in Clark County, NV, and San Bernardino, CA, and from 19 captive tortoises in Clark County, NV, was collected and evaluated for genes indicative of physiological status. Statistical analysis using a priori groupings indicated significant differences among groups for several genes, while multidimensional scaling and cluster analyses of transcription C T values indicated strong differentiation of a large cluster and multiple outlying individual tortoises or small clusters in multidimensional space. These analyses highlight the effectiveness of the gene panel at detecting environmental perturbations as well as providing guidance in determining the health of the desert tortoise.

California, Nevada↗
USGS2018

Impact of sylvatic plague vaccine on non-target small rodents in grassland ecosystems

Oral vaccination is an emerging management strategy to reduce the prevalence of high impact infectious diseases within wild animal populations. Plague is a flea-borne zoonosis of rodents that often decimates prairie dog ( Cynomys spp.) colonies in the western USA. Recently, an oral sylvatic plague vaccine (SPV) was developed to protect prairie dogs from plague and aid recovery of the endangered black-footed ferret ( Mustela nigripes ). Although oral vaccination programs are targeted toward specific species, field distribution of vaccine-laden baits can result in vaccine uptake by non-target animals and unintended indirect effects. We assessed the impact of SPV on non-target rodents at paired vaccine and placebo-treated prairie dog colonies in four US states from 2013 to 2015. Bait consumption by non-target rodents was high (70.8%, n = 3113), but anti-plague antibody development on vaccine plots was low (23.7%, n = 266). In addition, no significant differences were noted in combined deer mice ( Peromyscus maniculatus ) and western harvest mouse ( Reithrodontomys megalotis ) abundance or community evenness and richness of non-target rodents between vaccine-treated and placebo plots. In our 3-year field study, we could not detect a significant positive or negative effect of SPV application on non-target rodents.

EcoHealth↗
USGS2015

The influence of disturbed habitat on the spatial ecology of Argentine black and white tegu ( Tupinambis merianae ), a recent invader in the Everglades ecosystem (Florida, USA)

The threat of invasive species is often intensified in disturbed habitat. To optimize control programs, it is necessary to understand how degraded habitat influences the behavior of invasive species. We conducted a radio telemetry study to characterize movement and habitat use of introduced male Argentine black and white tegus ( Tupinambis merianae ) in the Everglades of southern Florida from May to August 2012 at the core and periphery of the introduced range. Tegus at the periphery moved farther per day (mean 131.7 ± 11.6 m, n = 6) compared to tegus at the core (mean 50.3 ± 12.4 m, n = 6). However, activity ranges were not significantly smaller in the core (mean 19.4 ± 8.4 ha, n = 6) compared to periphery (mean 29.1 ± 5.2 ha, n = 6). Peripheral activity ranges were more linear due to activity being largely restricted to levee habitat surrounded by open water or marsh. Tegus were located in shrub or tree habitat (mean 96%) more often than expected based on random locations (mean 58%), and the percent cover of trees and shrubs was higher in activity ranges (mean 61%) than the general study area (17%). Our study highlighted the ability of tegus to spread across the Florida landscape, especially in linear disturbed habitats where increased movement occurred and in areas of altered hydrology where movement is not restricted by water.

Florida↗
USGS2017

Riparian bird density decline in response to biocontrol of Tamarix from riparian ecosystems along the Dolores River in SW Colorado, USA

Biocontrol of invasive tamarisk ( Tamarix spp.) in the arid Southwest using the introduced tamarisk beetle ( Diorhabda elongata ) has been hypothesized to negatively affect some breeding bird species, but no studies to date have documented the effects of beetle-induced defoliation on riparian bird abundance. We assessed the effects of tamarisk defoliation by monitoring defoliation rates, changes in vegetation composition, and changes in density of six obligate riparian breeding bird species at two sites along the Dolores River in Colorado following the arrival of tamarisk beetles. We conducted bird point counts from 2010 to 2014 and modeled bird density as a function of native vegetation density and extent of defoliation using hierarchical distance sampling. Maximum annual defoliation decreased throughout the study period, peaking at 32–37% in 2009–2010 and dropping to 0.5–15% from 2011–2014. Stem density of both tamarisk and native plants declined throughout the study period until 2014. Density of all bird species declined throughout most of the study, with Song Sparrow disappearing from the study sites after 2011. Blue Grosbeak, Yellow-breasted Chat, and Yellow Warbler densities were negatively related to defoliation in the previous year, while Lazuli Bunting exhibited a positive relationship with defoliation. These findings corroborate earlier predictions of species expected to be sensitive to defoliation as a result of nest site selection. Tamarisk defoliation thus had short-term negative impacts on riparian bird species; active restoration may be needed to encourage the regrowth of native riparian vegetation, which in the longer-term may result in increased riparian bird density.

Colorado↗
USGS2020

Regime change in a large-floodplain river ecosystem: Patterns in body-size and functional biomass indicate a shift in fish communities

Changes in species dominance may drive regime shifts because dominant biotic feedbacks reflect functional traits of a community. Changes in species dominance has been documented by a 25-year fish community dataset encompassing six reaches of the Upper Mississippi and Illinois Rivers. Specifically, common carp ( Cyprinus carpio ) abundance has declined across all reaches, whereas silver carp ( Hypophthalmichthys molitrix ) and bighead carp ( Hypophthalmichthys nobilis ) have increased in abundance in the southern three reaches. To test whether signals in the data were consistent with regime transitions, changes in body-size patterns and trends in functional biomass and variance of functional biomass of the fish community were assessed. I further explored biomass thresholds relative to transitions. Shifts in body-size aggregations and trends in functional biomass support hypotheses that transitions from common carp dominance to a more functional diverse community represent alternate regimes. Results indicate such transitions occurred in the early 2000s for the two most northern reaches, and that the third most northern reach is nearing this transition. In the southern reaches, results indicate that transitions from common carp dominance to silver and bighead carp dominance also represent alternate regimes. Regime transitions support biomass thresholds between 8000 and 10,000 g per unit of day electrofishing effort of common carp and between 20 and 2000 g per unit effort in silver and bighead carp. Consistencies across reaches with similar dominance patterns provide support that reinforcing feedbacks, unique to the functional attributes of the dominant species, occur at similar biomass levels. Building knowledge of such feedback mechanisms is imperative to effectively manage for desired regimes.

Upper Mississippi River↗
USGS2017

The concurrent use of novel soil surface microclimate measurements to evaluate CO2 pulses in biocrusted interspaces in a cool desert ecosystem

Carbon cycling associated with biological soil crusts, which occupy interspaces between vascular plants in drylands globally, may be an important part of the coupled climate-carbon cycle of the Earth system. A major challenge to understanding CO 2 fluxes in these systems is that much of the biotic and biogeochemical activity occurs in the upper few mm of the soil surface layer (i.e., the ‘mantle of fertility’), which exhibits highly dynamic and difficult to measure temperature and moisture fluctuations. Here, we report a multi-sensor approach to simultaneously measuring temperature and moisture of this biocrust surface layer (0–2 mm), and the deeper soil profile, concurrent with automated measurement of surface soil CO 2 effluxes. Our results illuminate robust relationships between biocrust water content and field CO 2 pulses that have previously been difficult to detect and explain. All observed CO 2 pulses over the measurement period corresponded to surface wetting events, including when the wetting events did not penetrate into the soil below the biocrust layer (0–2 mm). The variability of temperature and moisture of the biocrust surface layer was much greater than even in the 0–5 cm layer of the soil beneath the biocrust, or deeper in the soil profile. We therefore suggest that coupling surface measurements of biocrust moisture and temperature to automated CO 2 flux measurements may greatly improve our understanding of the climatic sensitivity of carbon cycling in biocrusted interspaces in our study region, and that this method may be globally relevant and applicable.

Biogeochemistry↗
USGS2010

Nitrogen and phosphorus in the Upper Mississippi River: Transport, processing, and effects on the river ecosystem

Existing research on nutrients (nitrogen and phosphorus) in the Upper Mississippi River (UMR) can be organized into the following categories: (1) Long-term changes in nutrient concentrations and export, and their causes; (2) Nutrient cycling within the river; (3) Spatial and temporal patterns of river nutrient concentrations; (4) Effects of elevated nutrient concentrations on the river; and (5) Actions to reduce river nutrient concentrations and flux. Nutrient concentration and flux in the Mississippi River have increased substantially over the last century because of changes in land use, climate, hydrology, and river management and engineering. As in other large floodplain rivers, rates of processes that cycle nitrogen and phosphorus in the UMR exhibit pronounced spatial and temporal heterogeneity because of the complex morphology of the river. This spatial variability in nutrient processing creates clear spatial patterns in nutrient concentrations. For example, nitrate concentrations generally are much lower in off-channel areas than in the main channel. The specifics of in-river nutrient cycling and the effects of high rates of nutrient input on UMR have been less studied than the factors affecting nutrient input to the river and transport to the Gulf of Mexico, and important questions concerning nutrient cycling in the UMR remain. Eutrophication and resulting changes in river productivity have only recently been investigated the UMR. These recent studies indicate that the high nutrient concentrations in the river may affect community composition of aquatic vegetation (e. g., the abundance of filamentous algae and duckweeds), dissolved oxygen concentrations in off-channel areas, and the abundance of cyanobacteria. Actions to reduce nutrient input to the river include changes in land-use practices, wetland restoration, and hydrological modifications to the river. Evidence suggests that most of the above methods can contribute to reducing nutrient concentration in, and transport by, the UMR, but the impacts of mitigation efforts will likely be only slowly realized. ?? USGS, US Government 2010.

Hydrobiologia↗
USGS2026

Invasion potential of nonnative fishes through a large western dam into an iconic and vulnerable ecosystem

Native fishes face imperilment due to habitat loss and fragmentation, megadrought, invasive species, and synergies amongst threats. These threats coalesce at Glen Canyon Dam (GCD), which impounds the Colorado River to create Lake Powell, a reservoir inhabited by a suite of nonnative fishes. Water level in Lake Powell has declined precipitously due to water overallocation and megadrought, increasing the risk of nonnative fish entrainment through the dam, as the penstocks draw water from the epilimnion. Our goal was to characterize the distribution and abundance of nonnative fishes in the vicinity of GCD and identify environmental conditions that may increase entrainment. We used active and passive sampling, hydroacoustics, and acoustic telemetry to assess the distribution and abundance of fishes. When the reservoir was stratified fish remained in the epilimnion, were present near the GCD penstocks, and thus at high risk of entrainment. When the reservoir was mixed, fish generally occupied shallower, warmer areas further from GCD, but this varied among species. The distribution of nonnative fish and accompanying risk of entrainment varied by season and epilimnion depth. Retaining more water in Lake Powell to draw water from below the thermocline would reduce the risk of nonnative fish entrainment into Grand Canyon.

Arizona, Utah↗
USGS2024

Historical insights, current challenges: Tracking marine biodiversity in an urban harbor ecosystem in the face of climate change

The Boston Harbor Islands is the only coastal drumlin archipelago in the USA, featuring a distinctive and uncommon geological intertidal habitat known as mixed coarse substrate, which supports a range of coastal species and ecological processes. Recently designated as one of America’s 11 most endangered historic places due to climate change impacts, coastal adaptation and restoration efforts are crucial to their preservation. Such efforts can benefit from historic and current knowledge of endemic and emergent biodiversity. To investigate broad trends in coastal biodiversity, we compiled an inventory of marine coastal macroalgae, macroinvertebrates, fish, mammals, and shorebirds observed in the harbor since 1861. Records span 159 years, consisting of 451 unique taxa from 19 phyla. Analysis of average taxonomic distinctness (AvTD) revealed increases in diversity towards the end of the twentieth and early twenty-first century, likely associated with improved water quality (dissolved oxygen; AvTD > 85, p = 0.01) due to harbor restoration in the 1980s. Macroinvertebrates comprised 50% of the records, making this the most diverse taxonomic group in the time series. A significant increase of non-indigenous species, primarily macroinvertebrates and macroalgae, was observed over the last 20 years near human infrastructure and across multiple islands, a consequence of global change and characteristic of most urban harbors. The mixed coarse intertidal habitat, which makes up > 70% of Boston Harbor’s inner islands and supports high macroinvertebrate and macroalgal diversity (47% of species records), is not routinely monitored; our findings serve as a foundational resource for climate adaptation projects and decision-making.

Massachusetts↗
USGS2011

Managed flood effects on beaver pond habitat in a desert riverine ecosystem, bill williams river, Arizona USA

The ecological effects of beaver in warm-desert streams are poorly documented, but potentially significant. For example, stream water and sediment budgets may be affected by increased evaporative losses and sediment retention in beaver ponds. We measured physical attributes of beaver pond and adjacent lotic habitats on a regulated Sonoran Desert stream, the Bill Williams River, after ???11 flood-free months in Spring 2007 and Spring 2008. Neither a predicted warming of surface water as it passed through a pond nor a reduction in dissolved oxygen in ponds was consistently observed, but bed sediment sorted to finest in ponds as expected. We observed a river segment-scale downstream rise in daily minimum stream temperature that may have been influenced by the series of ??100 beaver ponds present. Channel cross-sections surveyed before and after an experimental flood (peak flow 65 m3/s) showed net aggradation on nine of 13 cross-sections through ponds and three of seven through lotic reaches. Our results indicate that beaver affect riverine processes in warm deserts much as they do in other biomes. However, effects may be magnified in deserts through the potential for beaver to alter the stream thermal regime and water budget. ?? Society of Wetland Scientists 2011.

Wetlands↗
USGS2016

Ecosystem level methane fluxes from tidal freshwater and brackish marshes of the Mississippi River Delta: Implications for coastal wetland carbon projects

Sulfate from seawater inhibits methane production in tidal wetlands, and by extension, salinity has been used as a general predictor of methane emissions. With the need to reduce methane flux uncertainties from tidal wetlands, eddy covariance (EC) techniques provide an integrated methane budget. The goals of this study were to: 1) establish methane emissions from natural, freshwater and brackish wetlands in Louisiana based on EC; and 2) determine if EC estimates conform to a methane-salinity relationship derived from temperate tidal wetlands with chamber sampling. Annual estimates of methane emissions from this study were 62.3 g CH 4 /m 2 /yr and 13.8 g CH 4 /m 2 /yr for the freshwater and brackish (8–10 psu) sites, respectively. If it is assumed that long-term, annual soil carbon sequestration rates of natural marshes are ~200 g C/m 2 /yr (7.3 tCO 2 e/ha/yr), healthy brackish marshes could be expected to act as a net radiative sink, equivalent to less than one-half the soil carbon accumulation rate after subtracting methane emissions (4.1 tCO 2 e/ha/yr). Carbon sequestration rates would need case-by-case assessment, but the EC methane emissions estimates in this study conformed well to an existing salinity-methane model that should serve as a basis for establishing emission factors for wetland carbon offset projects.

Louisiana↗
USGS1989

A macrophyte submodel for aquatic ecosystems

A macrophyte submodel has been incorporated and tested in CE-QUAL-R1, a one-dimensional, vertically averaged model of reservoir water quality. A quasi two-dimensional scheme was necessary to represent the spatial relationship of macrophytes in reservoirs adequately. The macrophyte processes modeled were photosynthesis, dark respiration, excretion and nonpredatory mortality. Process equations for photosynthesis as a function of light and temperature, and dark respiration as a function of temperature were tested using data from laboratory studies. The submodel was field tested, along with other components of CE-QUAL-R1, using data collected at Eau Galle Reservoir, WI, U.S.A.

Wisconsin↗
USGS2016

Invasive species: Ocean ecosystem case studies for earth systems and environmental sciences

Marine species are increasingly transferred from areas where they are native to areas where they are not. Some nonnative species become invasive, causing undesirable impacts to environment, economy and/or human health. Nonnative marine species can be introduced through a variety of vectors, including shipping, trade, inland corridors (such as canals), and others. Effects of invasive marine species can be dramatic and irreversible. Case studies of four nonnative marine species are given (green crab, comb jelly, lionfish and Caulerpa algae).

Earth Systems and Environmental Sciences↗
USGS2022

Worldwide wetland loss and conservation of biodiversity and ecosystem services

Aim : Best strategies for future conservation and management to address global and regional trends in wetland loss and degradation are assessed in this article. Main concepts covered : Direct drivers of wetland loss and change include land drainage and filling, hydrologic alteration, degradation from pollutants and sediments, and conversion to agriculture, urban and industrial usage. Estimates of global wetland loss are as high as 87% since 1700 CE. All regions of the world have lost wetland area. The designation of wetland protected area reduces disturbance by humans and supports the conservation of biodiversity and habitat. Protected areas have been designated by local, state, or federal entities, NGOs (e.g., Nature Conservancy), and the Ramsar Convention on Wetlands. Protected wetlands have great value for human society. For example, wetlands such as peatland and swamp store carbon that would otherwise be released as greenhouse gases to the atmosphere. A case study of the Keoladeo National Park, Rajasthan, India underscores the importance of maintaining water supply to maintain aquatic vegetation in protected wetlands. Conclusion/outlook : Given the combined stresses of land-use and climate change to wetland protected areas, management of altered wetlands may improve their function. Beneficial management actions can include freshwater remediation of hydrologically-altered floodplains, improved wetland reserve design, assisted migration, and the softening of burning/cutting during drought. A better knowledge of potential of management actions to remediate land-use change will be helpful in addressing protected area management to promote conservation in the future.

Book chapter↗
USGS2022

Biological assessments of aquatic ecosystems

The aim of biological assessments (or bioassessments) is to provide decision makers and managers the scientific information and tools needed to protect and restore aquatic life. Biological assessments typically include several critical elements, including development of ecological indicators, indices of ecological status, benchmarks by which to gauge impairment, ways to identify the stressors causing ecological impairment, and biological criteria and standards to protect aquatic life. New scientific tools are emerging that should improve the accuracy and precision of biological assessments, but the major challenges to effective protection and restoration of aquatic life are political and economic rather than scientific.

Book chapter↗