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At least 685 records · Page 38Linked to original sources
USGS2012

Long-distance swimming by polar bears (Ursus maritimus) of the southern Beaufort Sea during years of extensive open water

Polar bears ( Ursus maritimus Phipps, 1774) depend on sea ice for catching marine mammal prey. Recent sea-ice declines have been linked to reductions in body condition, survival, and population size. Reduced foraging opportunity is hypothesized to be the primary cause of sea-ice-linked declines, but the costs of travel through a deteriorated sea-ice environment also may be a factor. We used movement data from 52 adult female polar bears wearing Global Positioning System (GPS) collars, including some with dependent young, to document long-distance swimming (>50 km) by polar bears in the southern Beaufort and Chukchi seas. During 6 years (2004-2009), we identified 50 long-distance swims by 20 bears. Swim duration and distance ranged from 0.7 to 9.7 days (mean = 3.4 days) and 53.7 to 687.1 km (mean = 154.2 km), respectively. Frequency of swimming appeared to increase over the course of the study. We show that adult female polar bears and their cubs are capable of swimming long distances during periods when extensive areas of open water are present. However, long-distance swimming appears to have higher energetic demands than moving over sea ice. Our observations suggest long-distance swimming is a behavioral response to declining summer sea-ice conditions.

Canadian Journal of Zoology↗
USGS2013

Experimental reintroduction reveals novel life-history variation in Laysan Ducks ( Anas laysanensis )

Subfossil remains indicate that the Laysan Duck ( Anas laysanensis ) formerly occurred throughout the Hawaiian archipelago, but for more than 150 years it has been confined to a single, small atoll in the northwestern chain, Laysan Island. In 2004–2005, 42 ducks were reintroduced from Laysan to Midway Atoll, where they exhibited variation in life history never observed on Laysan. On Laysan, females have never been observed to breed successfully at age 1 year and few attempt it, whereas on Midway, females routinely raised young at <1 year of age. Mean (± SD) clutch size on Midway (7.0 ± 1.1, n = 41) was larger than the maximum clutch size of six eggs observed on Laysan. On Midway, renesting following nest failure (0.55 probability, n = 27) and double brooding (0.50, n = 54) were routine, and two instances of triple brooding were observed, whereas on Laysan, renesting and double brooding are rare (0.05 probability for both during our study; n = 21 and 19, respectively) and triple brooding has never been observed. Other novel life history on Midway included early cessation of parental care to renest. Altered life history on Midway is likely related to better feeding conditions and low population density compared with Laysan. An especially intriguing possibility is that the phenotypic plasticity observed represents exposure of hidden reaction norms evolved when the species inhabited a range of environments, but several alternative explanations exist. Future reintroductions of this species may provide opportunities to test hypotheses about mechanisms underlying phenotypic plasticity.

Hawai'i↗
USGS1995

Desert tortoises in the Mojave and Colorado deserts

The desert tortoise ( Gopherus agassizii ) is a widespread species of the southwestern United States and Mexico. Within the United States, desert tortoises live in the Mojave, Colorado, and Sonoran deserts of southeastern California, southern Nevada, southwestern Utah, and western Arizona (Fig. 1). A substantial portion of the habitat is on lands administered by the U.S. Department of the Interior. The U.S. government treats the desert tortoise as an indicator or umbrella species to measure the health and well-being of the ecosystems it inhabits. The tortoise functions well as an indicator because it is long-lived, takes 12-20 years to reach reproductive maturity, and is sensitive to changes in the environment. In 1990 the U.S. Fish and Wildlife Service listed the species as threatened in the northern and western parts of its geographic range (Fig. 1) because of widespread population declines and overall habitat loss, deterioration, and fragmentation. Because some populations exhibit significant genetic, morphologic (see glossary), and behavioral differences, the Desert Tortoise Recovery Team identified six distinctive population segments (Fig. 1) for critical habitat protection and long-term conservation within the Mojave and Colorado deserts (e.g., Lamb et al. 1989; USFWS 1994). The population segments are representative of distinctive climatic, floristic, and geographic regions.

Arizona, California, Nevada, Utah↗
USGS1993

Coupled effects of vertical mixing and benthic grazing on phytoplankton populations in shallow, turbid estuaries

Coastal ocean waters tend to have very different patterns of phytoplankton biomass variability from the open ocean, and the connections between physical variability and phytoplankton bloom dynamics are less well established for these shallow systems. Predictions of biological responses to physical variability in these environments is inherently difficult because the recurrent seasonal patterns of mixing are complicated by aperiodic fluctuations in river discharge and the high-frequency components of tidal variability. We might expect, then, less predictable and more complex bloom dynamics in these shallow coastal systems compared with the open ocean. Given this complex and dynamic physical environment, can we develop a quantitative framework to define the physical regimes necessary for bloom inception, and can we identify the important mechanisms of physical-biological coupling that lead to the initiation and termination of blooms in estuaries and shallow coastal waters? Numerical modeling provides one approach to address these questions. Here we present results of simulation experiments with a refined version of Cloern's (1991) model in which mixing processes are treated more realistically to reflect the dynamic nature of turbulence generation in estuaries. We investigated several simple models for the turbulent mixing coefficient. We found that the addition of diurnal tidal variation to Cloern's model greatly reduces biomass growth indicating that variations of mixing on the time scale of hours are crucial. Furthermore, we found that for conditions representative of South San Francisco Bay, numerical simulations only allowed for bloom development when the water column was stratified and when minimal mixing was prescribed in the upper layer. Stratification, however, itself is not sufficient to ensure that a bloom will develop: minimal wind stirring is a further prerequisite to bloom development in shallow turbid estuaries with abundant populations of benthic suspension feeders.

Journal of Marine Research↗
USGS2002

Mechanisms of impact and potential recovery of nearshore vertebrate predators following the 1989 Exxon Valdez oil spill

The 1989 spill of some 42 million L of crude oil into Prince William Sound, Alaska, represents not only the largest tanker spill in United States history, but the world’s largest spill in northern waters. Acute effects have been studied extensively. However, efforts to quantify the spill’s long-term chronic effects and develop defensible restoration measures have been plagued by varying levels of scientific uncertainty. That such uncertainty exists is not unexpected. The spill occurred in Prince William Sound’s highly variable physical setting typified by its complex oceanography and fjord-like geomorphology. Additionally, uncertainty was driven by the scarcity of precise pre-spill population estimates and spotty life-history information for most species. The research reported herein in, structured in eight primary papers and 27 supporting papers (appendices), documents the state of recovery and assessments of continuing constraints to population recovery for four vertebrate predators (sea otter Enhydra lutris , harlequin duck Histrionicus histrionicus , river otter Lontra canadensis , and pigeon guillemot Cepphus columba ) whose recovery status remained uncertain some 5 years after the Exxon Valdez oil spill. These species are used in a collective weight of evidence approach to better understand the process of coastal community recovery. Each species is examined for the strength of information it brings in health, population, and trophic metrics to support or reject the hypothesis of continuing oil effects in the nearshore system versus the alternatives that food constraints or demographic bottlenecks limit these focal species. While data for individual species contain various levels of uncertainty, scientific confidence is developed in the following picture when examined across species, metric, and hypothesis: Within the nearshore coastal environment, sporadic releases of residual oil are occurring, and benthic species, primarily invertebrates, are being exposed in a temporally and spatially patchy manner sufficient to transport oil up through the food chain. Thus, for the two invertebrate-feeders, sea otter and harlequin duck, evidence exists over several lines of investigation to suggest that local-scale populations continue to be constrained not by food availability or natural demographic processes, but by increased levels of mortality coincident with continued exposure to residual oil. Conversely, weight of evidence suggests that only limited direct oil-related effects are being transferred through the fish trophic pathway. Sufficient evidence suggests recovery is occurring in river otter populations, while the lack of recovery in pigeon guillemot may be attributed to food limitations (both natural and indirectly related to the spill) and/or slow demographic response to initial acute mortalities. Individual lines of investigation often contained uncertainty, but the collective weight of evidence presented in this multipaper volume indicates lack of full recovery of the nearshore ecosystem from the Exxon Valdez oil spill nearly a decade following the event. Integrated, multispecies approaches can allow sufficient weight of evidence to develop despite inherent system variability or data limitations and, thus, facilitate both better societal understanding of such pollution events and development of appropriate restoration responses.

Alaska↗
USGS2026

Navigating uncertainty and competing objectives: Spring chinook salmon recovery in the upper Willamette river

Globally, anadromous fish populations are threatened with extinction due to multiple factors, including river impoundments that block migration, widespread alteration of physical habitat, temperature, and flow regimes, commercial and recreational harvest, changes in biological communities, and long-term climate trends. In this synthesis, we describe how physical and biological factors, policy and law, and public resource allocation affect management of spring-run Chinook Salmon ( Oncorhynchus tshawytscha ) in the Upper Willamette River (UWR), Oregon, USA. Efforts to restore salmon populations often involve trade-offs, for example, water management decisions must account for flood control, agricultural and municipal water use, and management of other species. UWR Chinook Salmon recovery efforts are also governed by multiple laws, policies, and action agencies that in some cases have incongruent objectives. Competing and conflicting objectives, combined with uncertainty regarding the outcomes of proposed management actions, create significant challenges for decision makers. Resource limitations, regulatory constraints, and incongruent objectives have created challenges for managers in the UWR, but opportunities exist for improved adaptive management and collaboration, which could build trust and engagement among stakeholders and ultimately support the successful implementation of decision tools. A suite of decision support tools that have been used in the Willamette River basin and elsewhere across the range of Pacific salmon have the potential to enhance decision processes. These tools can be effective when decision makers and stakeholders commit to long-term, collaborative utilization of the tools for decision making, and when available resources and regulatory environments are conducive to implementation and adaptive refinement of both the decision-support tools and management plans. The general biological and institutional principles discussed for UWR Chinook Salmon in this work apply more generally to populations of anadromous fishes across their range, especially to populations in highly regulated river systems.

Oregon↗
USGS2022

Depth drives growth dynamics of dreissenid mussels in Lake Ontario

Understanding dreissenid mussel population dynamics and their impacts on lake ecosystems requires quantifying individual growth across a range of habitats. Most dreissenid mussel growth rates have been estimated in nutrient rich or nearshore environments, but mussels have continued to expand into deep, cold, low-nutrient habitats of the Great Lakes. We measured annual quagga mussel ( Dreissena rostriformis bugensis) growth at 15 m, 45 m, and 90 m in Lake Ontario using caged mussels near Oswego, New York, USA from June 2018 to May 2019. Quagga mussel growth (starting size 12 mm) was greatest at 15 m (mean shell length increase = 10.2 mm), and was lower at 45 m (5.9 mm) and 90 m (0.7 mm). Caged mussels were obtained from near the 90-m site and those reared at 15 and 45 m developed thicker shells than those that were caged at 90 m. We observed relatively high colonization by quagga and, to a lesser degree, zebra mussels ( Dreissena polymorpha ) at 15 m, very few colonizers at 45 m, and none at 90 m. Higher growth potential, but low natural mussel densities observed at 15 m and 45 m suggest factors other than growth limit dreissenid abundance at these depths. The relatively slow dreissenid growth rates observed in offshore habitats are consistent with the gradual abundance increases documented in these zones across the Great Lakes and suggest new mussels that become established in these habitats may contribute to ecosystem effects for decades.

New York↗
USGS2017

New zircon (U-Th)/He and U/Pb eruption age for the Rockland tephra, western USA

Eruption ages of a number of prominent Quaternary volcanic deposits remain inaccurately and/or imprecisely constrained, despite their importance as regional stratigraphic markers in paleo-environment reconstruction and as evidence of climate-altering eruptions. Accurately dating volcanic deposits presents challenging analytical considerations, including poor radiogenic yield, scarcity of datable minerals, and contamination of crystal populations by magma, eruption, and transport processes. One prominent example is the Rockland tephra, which erupted from the Lassen Volcanic Center in the southern Cascade arc. Despite a range in published eruption ages from 0.40 to 0.63 Ma, the Rockland tephra is extensively used as a marker bed across the western United States. To more accurately and precisely constrain the age of the Rockland tephra-producing eruption, we report U/Pb crystallization dates from the outermost ∼2 μm of zircon crystal faces (surfaces) using secondary ion mass spectrometry (SIMS). Our new weighted mean 238 U/ 206 Pb age for Rockland tephra zircon surfaces is 0.598 ± 0.013 Ma (2σ) and MSWD = 1.11 (mean square weighted deviation). As an independent test of the accuracy of this age, we obtained new (U-Th)/He dates from individual zircon grains from the Rockland tephra, which yielded a weighted mean age of 0.599 ± 0.012 Ma (2σ, MSWD = 5.13). We also obtained a (U-Th)/He age of 0.628 ± 0.014 Ma (MSWD = 1.19) for the Lava Creek Tuff member B, which was analyzed as a secondary standard to test the accuracy of the (U-Th)/He technique for Quaternary tephras, and to evaluate assumptions made in the model-age calculation. Concordance of new U/Pb and (U-Th)/He zircon ages reinforces the accuracy of our preferred Rockland tephra eruption age, and confirms that zircon surface dates sample zircon growth up to the time of eruption. We demonstrate the broad applicability of coupled U/Pb zircon-surface and single-grain zircon (U-Th)/He geochronology to accurate dating of Quaternary tephra, and highlight the challenges and opportunities of this technique.

Quaternary Science Reviews↗
USGS2016

Investigating dynamic sources of pharmaceuticals: Demographic and seasonal use are more important than down-the-drain disposal in wastewater effluent in a University City setting

Pharmaceutical pollution in surface waters poses risks to human and ecosystem health. Wastewater treatment facilities are primary sources of pharmaceutical pollutants, but little is known about the factors that affect drugs entering the wastewater stream. This paper investigates the effects of student pharmaceutical use and disposal behaviors and an annual demographic shift on pharmaceutical pollution in a university town. We sampled wastewater effluent during a ten-day annual spring student move-out period at the University of Vermont. We then interpreted these data in light of survey results that investigated pharmaceutical purchasing, use, and disposal practices among the university student population. Surveys indicated that the majority of student respondents purchased pharmaceuticals in the previous year. Many students reported having leftover drugs, though only a small portion disposed of them, mainly in the trash. We detected 51 pharmaceuticals in 80% or more of the wastewater effluent samples collected over the ten-day sampling period. Several increased in concentration after students left the area. Concentrations of caffeine and nicotine decreased weakly. Drug disposal among this university student population does not appear to be a major source of pharmaceuticals in wastewater. Increases in pharmaceutical concentration after the students left campus can be tied to an increase in the seasonal use of allergy medications directly related to pollen, as well as a demographic shift to a year-round older population, which supports national data that older people use larger volumes and different types of pharmaceuticals than the younger student population.

Vermont↗
USGS2026

Growth form and lifespan of herbaceous species mediate the role of traits in short-term drought response

Increased climate variability is expected to intensify short-term drought events. Plants have evolved stress tolerance strategies involving trade-offs in resource conservation, mycorrhizal collaboration and plant size, yet how these strategies promote drought resistance across different herbaceous plant groups remains unknown. Leveraging 63 globally distributed grassland and shrubland sites from the International Drought Experiment, we identified plant traits linked to drought resistance in 661 populations of 421 species after 1 year of extreme drought. We assessed how traits, site precipitation and drought severity affected cover change across growth forms and lifespans, and how trait–environment interactions influenced drought resistance. Across all species, leaf N (an acquisitive trait) was associated with drought resistance, whereas in forbs, drought resistance was also associated with a conservative root trait and plant size. In addition, interactions among traits mediated drought resistance; root traits predicted performance only in concert with other traits. Environmental variables influenced trait effects on drought resistance, notably for annuals in wetter sites, suggesting that drought-escape strategies in annuals may be advantageous only under mild stress. Our study highlights variability in traits that predict drought resistance across herbaceous plant groups, emphasizing the importance of species context, environmental stress and the selection of traits in research and management.

Nature Ecology and Evolution↗
USGS2012

Evidence of local adaptation in westslope cutthroat trout

An understanding of the process of local adaptation would allow managers to better protect and conserve species. Many salmonids are in need of such efforts, and because they often persist in differing, isolated environments, they are useful organisms for studying local adaptation. In addition, the temperature sensitivity of salmonids provides a likely target for natural selection. We studied thermal adaptation in four wild populations and one hatchery stock of westslope cutthroat trout Oncorhynchus clarkii lewisi . The mean summer temperatures of source streams ranged from 6.7°C to 11.2°C. Embryos were collected from the wild, and embryonic development, embryonic survival, and juvenile growth were determined. A significant relationship between median embryonic survival and source stream temperature was detected. Based on a rank test, populations from colder streams had a greater decline in median embryonic survival at warm temperatures than populations from warmer streams. Embryonic development and juvenile growth did not appear to be influenced by source. These findings suggest that populations are thermally adapted to their source streams and this should be considered by managers. However, further study is necessary to sort out the potential confounding factors, whether genetic or epigenetic.

Transactions of the American Fisheries Society↗
USGS2023

Sound and sturgeon: Bioacoustics and anthropogenic sound

Sturgeons are basal bony fishes, most species of which are considered threatened and/or endangered. Like all fishes, sturgeons use hearing to learn about their environment and perhaps communicate with conspecifics, as in mating. Thus, anything that impacts the ability of sturgeon to hear biologically important sounds could impact fitness and survival of individuals and populations. There is growing concern that the sounds produced by human activities (anthropogenic sound), such as from shipping, commercial barge navigation on rivers, offshore windfarms, and oil and gas exploration, could impact hearing by aquatic organisms. Thus, it is critical to understand how sturgeon hear, what they hear, and how they use sound. Such data are needed to set regulatory criteria for anthropogenic sound to protect these animals. However, very little is known about sturgeon behavioral responses to sound and their use of sound. To help understand the issues related to sturgeon and anthropogenic sound, this review first examines what is known about sturgeon bioacoustics. It then considers the potential effects of anthropogenic sound on sturgeon and, finally identifies areas of research that could substantially improve knowledge of sturgeon bioacoustics and effects of anthropogenic sound. Filling these gaps will help regulators establish appropriate protection for sturgeon.

The Journal of the Acoustical Society of America↗
USGS2016

Exploring climate niches of ponderosa pine (Pinus ponderosa Douglas ex Lawson) haplotypes in the western United States: Implications for evolutionary history and conservation

Ponderosa pine ( Pinus ponderosa Douglas ex Lawson) occupies montane environments throughout western North America, where it is both an ecologically and economically important tree species. A recent study using mitochondrial DNA analysis demonstrated substantial genetic variation among ponderosa pine populations in the western U.S., identifying 10 haplotypes with unique evolutionary lineages that generally correspond spatially with distributions of the Pacific ( P . p . var. ponderosa ) and Rocky Mountain ( P . p . var. scopulorum ) varieties. To elucidate the role of climate in shaping the phylogeographic history of ponderosa pine, we used nonparametric multiplicative regression to develop predictive climate niche models for two varieties and 10 haplotypes and to hindcast potential distribution of the varieties during the last glacial maximum (LGM), ~22,000 yr BP. Our climate niche models performed well for the varieties, but haplotype models were constrained in some cases by small datasets and unmeasured microclimate influences. The models suggest strong relationships between genetic lineages and climate. Particularly evident was the role of seasonal precipitation balance in most models, with winter- and summer-dominated precipitation regimes strongly associated with P . p . vars. ponderosa and scopulorum , respectively. Indeed, where present-day climate niches overlap between the varieties, introgression of two haplotypes also occurs along a steep clinal divide in western Montana. Reconstructed climate niches for the LGM suggest potentially suitable climate existed for the Pacific variety in the California Floristic province, the Great Basin, and Arizona highlands, while suitable climate for the Rocky Mountain variety may have existed across the southwestern interior highlands. These findings underscore potentially unique phylogeographic origins of modern ponderosa pine evolutionary lineages, including potential adaptations to Pleistocene climates associated with discrete temporary glacial refugia. Our predictive climate niche models may inform strategies for further genetic research (e.g., sampling design) and conservation that promotes haplotype compatibility with projected changes in future climate.

PLoS ONE↗
USGS1997

Modeling changes in growth and diet on polychlorinated biphenyl bioaccumulation in Coregonus hoyi

Restrictions on the release of PCBs into the environment began in the early 1970s, resulting in reduced PCB concentrations in Lake Michigan bloaters ( Coregonus hoyi ). However, since 1980, PCB concentrations in bloater have declined only slightly. The bloater population also increased 40-fold during 1970 through 1984, resulting in a diet shift and a density-dependent decline in growth. Our goal was to determine how these changes in diet and growth may have affected PCB accumulation in Lake Michigan bloater. We evaluated the consequences of these two changes on bloater PCB concentrations by developing a bioenergetics-based PCB bioaccumulation model. Bloater PCB concentrations increased little when we increased the amount of Diporeia hoyi, the most contaminated prey, in the bloater diet. By comparing constant growth (similar to those of the 1970s) to observed decline in growth rates, we found that lower growth rates during the 1980s placed older, more contaminated bloaters in the size range most vulnerable to predators and in the size range sampled by PCB monitoring programs. Bloater PCB concentration trends may be influenced by the sampling methodology of the United States Geological Survey. If fish PCB trends are to be used as an indicator of system-level PCB trends, sampling should include a representative sample of fish of known age from the population.

Ecological Applications↗
USGS2018

Adaptive population divergence and directional gene flow across steep elevational gradients in a climate‐sensitive mammal

The American pika is a thermally sensitive, alpine lagomorph species. Recent climate-associated population extirpations and genetic signatures of reduced population sizes range-wide indicate the viability of this species is sensitive to climate change. To test for potential adaptive responses to climate stress, we sampled pikas along two elevational gradients (each ~470 to 1640 m) and employed three outlier detection methods, BAYESCAN, LFMM, and BAYPASS, to scan for genotype-environment associations in samples genotyped at 30,763 SNP loci. We resolved 173 loci with robust evidence of natural selection detected by either two independent analyses or replicated in both transects. A BLASTN search of these outlier loci revealed several genes associated with metabolic function and oxygen transport, indicating natural selection from thermal stress and hypoxia. We also found evidence of directional gene flow primarily downslope from large high-elevation populations and reduced gene flow at outlier loci, a pattern suggesting potential impediments to the upward elevational movement of adaptive alleles in response to contemporary climate change. Finally, we documented evidence of reduced genetic diversity associated the south-facing transect and an increase in corticosterone stress levels associated with inbreeding. This study suggests the American pika is already undergoing climate-associated natural selection at multiple genomic regions. Further analysis is needed to determine if the rate of climate adaptation in the American pika and other thermally sensitive species will be able to keep pace with rapidly changing climate conditions.

Washington↗
USGS1996

South Florida wetlands ecosystem; biogeochemical processes in peat

The South Florida wetlands ecosystem is an environment of great size and ecological diversity (figs. 1 and 2). The landscape diversity and subtropical setting of this ecosystem provide a habitat for an abundance of plants and wildlife, some of which are unique to South Florida. South Florida wetlands are currently in crisis, however, due to the combined effects of agriculture, urbanization, and nearly 100 years of water management. Serious problems facing this ecosystem include (1) phosphorus contamination producing nutrient enrichment, which is causing changes in the native vegetation, (2) methylmercury contamination of fish and other wildlife, which poses a potential threat to human health, (3) changes in the natural flow of water in the region, resulting in more frequent drying of wetlands, loss of organic soils, and a reduction in freshwater flow to Florida Bay, (4) hypersalinity, massive algal blooms, and seagrass loss in parts of Florida Bay, and (5) a decrease in wildlife populations, especially those of wading birds. This U.S. Geological Survey (USGS) project focuses on the role of organic-rich sediments (peat) of South Florida wetlands in regulating the concentrations and impact of important chemical species in the environment. The cycling of carbon, nitrogen, phosphorus, and sulfur in peat is an important factor in the regulation of water quality in the South Florida wetlands ecosystem. These elements are central to many of the contamination issues facing South Florida wetlands, such as nutrient enrichment, mercury toxicity, and loss of peat. Many important chemical and biological reactions occur in peat and control the fate of chemical species in wetlands. Wetland scientists often refer to these reactions as biogeochemical processes, because they are chemical reactions usually mediated by microorganisms in a geological environment. An understanding of the biogeochemical processes in peat of South Florida wetlands will provide a basis for evaluating the effects on water quality of (1) constructing buffer wetlands to alleviate nutrient contamination and (2) replumbing the ecosystem to restore natural water flow. The results may also suggest new approaches for solving problems of contamination and water quality in these wetlands. A second focus of this project will be on the geochemical history of the South Florida ecosystem. Peat is a repository of the history of past environmental conditions in the wetland. Before effective action can be taken to correct many of the problems facing these wetlands, we must first study the biogeochemistry of the peat at depth in order to understand whether current problems are the result of recent human activity or are part of a long-term natural cycle. Coordination with other (USGS) projects for South Florida is ongoing. These projects are studying the biological history of the ecosystem by using pollen and shells buried in the peat, together with procedures for dating the peat at various depths, to develop an overall ecosystem history model, with emphasis on the last 100 years.

Fact Sheet↗
USGS2014

Toxicity and accumulation of silver nanoparticles during development of the marine polychaete Platynereis dumerilii

Pollutants affecting species at the population level generate ecological instability in natural systems. The success of early life stages, such as those of aquatic invertebrates, is highly affected by adverse environmental conditions. Silver released into the environment from emerging nanotechnology represents such a threat. Sediments are sinks for numerous pollutants, which aggregate and/or associate with depositing suspended particles. Deposit feeder such as the annelid Platynereis dumerilii, which has a large associated literature on its development, is an excellent model organism for exposure studies in coastal environments. We exposed eggs, larvae, juveniles and adults of P. dumerilii to various concentrations of citrate (cit-Ag NPs) or humic acid (HA-Ag NPs) capped silver nanoparticles (Ag NPs) as well to dissolved Ag (added as AgNO3). We showed that mortality and abnormal development rate increased with younger life stages. While adults and juvenile were the most tolerant life stages, fertilized eggs were highly sensitive to AgNO3, cit-Ag NPs and HA-Ag NPs. Exposures to HA-Ag NPs triggered the highest cute toxicity responses in P. dumerilii and in most cases both Ag NPs were more toxic than AgNO3. Uptake rate of HA-Ag NPs in adult worms was also higher than from other Ag forms, consistent with toxicity to other life stages. The early stages of the life cycle of marine coastal organisms are more affected by Ag NPs than the juvenile or adult life stages, indicating that exposure experiments at the larval level contribute to realistic eco-toxicological studies in aquatic environments.

Science of the Total Environment↗
USGS2001

Environmental geochemistry at the global scale

Land degradation and pollution caused by population pressure and economic development pose a threat to the sustainability of the earth's surface, especially in tropical regions where a long history of chemical weathering has made the surface environment particularly fragile. Systematic baseline geochemical data provide a means of monitoring the state of the environment and identifying problem areas. Regional surveys have already been carried out in some countries, and with increased national and international funding they can be extended to cover the rest of the land surface of the globe. Preparations have been made, under the auspices of the International Union of Geological Surveys (IUGS) and the International Association of Geochemistry and Cosmochemistry (IAGC) for the establishment of just such an integrated global database. ?? 2001 NERC. Published by Elsevier Science Ltd.

Conference Paper↗