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At least 91 records · Page 5Linked to original sources
USGS2009

Nutrient availability and phytoplankton nutrient limitation across a gradient of atmospheric nitrogen deposition

Atmospheric nitrogen (N) deposition to lakes and watersheds has been increasing steadily due to various anthropogenic activities. Because such anthropogenic N is widely distributed, even lakes relatively removed from direct human disturbance are potentially impacted. However, the effects of increased atmospheric N deposition on lakes are not well documented, We examined phytoplankton biomass, the absolute and relative abundance of limiting nutrients (N and phosphorus [P]), and phytoplankton nutrient limitation in alpine lakes of the Rocky Mountains of Colorado (USA) receiving elevated (>6 kg N??ha -1 ??yr -1 ) or low (<2 kg N??ha -1 ??yr -1 ) levels of atmospheric N deposition. Highdeposition lakes had higher NO 3 -N and total N concentrations and higher total N : total P ratios. Concentrations of chlorophyll and seston carbon (C) were 2-2.5 times higher in highdeposition relative to low-deposition lakes, while high-deposition lakes also had higher seston C:N and C:P (but not N:P) ratios. Short-term enrichment bioassays indicated a qualitative shift in the nature of phytoplankton nutrient limitation due to N deposition, as highdeposition lakes had an increased frequency of primary P limitation and a decreased frequency and magnitude of response to N and to combined N and P enrichment. Thus elevated atmospheric N deposition appears to have shifted nutrient supply from a relatively balanced but predominantly N-deficient regime to a more consistently P-limited regime in Colorado alpine lakes. This adds to accumulating evidence that sustained N deposition may have important effects on lake phytoplankton communities and plankton-based food webs by shifting the quantitative and qualitative nature of nutrient limitation. ?? 2009 by the Ecological Society of America.

Ecology↗
USGS2015

Formation of mercury sulfide from Hg(II)−thiolate complexes in natural organic matter

Methylmercury is the environmental form of neurotoxic mercury that is biomagnified in the food chain. Methylation rates are reduced when the metal is sequestered in crystalline mercury sulfides or bound to thiol groups in macromolecular natural organic matter. Mercury sulfide minerals are known to nucleate in anoxic zones, by reaction of the thiol-bound mercury with biogenic sulfide, but not in oxic environments. We present experimental evidence that mercury sulfide forms from thiol-bound mercury alone in aqueous dark systems in contact with air. The maximum amount of nanoparticulate mercury sulfide relative to thiol-bound mercury obtained by reacting dissolved mercury and soil organic matter matches that detected in the organic horizon of a contaminated soil situated downstream from Oak Ridge, TN, in the United States. The nearly identical ratios of the two forms of mercury in field and experimental systems suggest a common reaction mechanism for nucleating the mineral. We identified a chemical reaction mechanism that is thermodynamically favorable in which thiol-bound mercury polymerizes to mercury–sulfur clusters. The clusters form by elimination of sulfur from the thiol complexes via breaking of mercury–sulfur bonds as in an alkylation reaction. Addition of sulfide is not required. This nucleation mechanism provides one explanation for how mercury may be immobilized, and eventually sequestered, in oxygenated surface environments.

Environmental Science & Technology↗
USGS2025

Arsenic accumulation in Sonora Mud Turtles (Kinosternon sonoriense) in an unusual freshwater food web

Montezuma Well is an unusual fishless, spring-fed, desert wetland in central Arizona. Water in the wetland is naturally enriched with > 100 µg/l dissolved geogenic arsenic (As) and supports a simple aquatic food web dominated by a small number of endemic invertebrate species that achieve high abundances. Previous studies of As among various environmental compartments and organisms in Montezuma Well did not include omnivorous Sonora Mud turtles ( Kinosternon sonoriense ) despite their potential importance in the As cycle by virtue of their substantial biomass and role as top predators. We measured As concentrations in water, sediment, and organisms (macrophytes, amphipods, insects, leeches, and turtles) representing a range of trophic levels in order to document the importance of turtles at the apex of the Montezuma Well food web and in the As cycle. Concentrations of As in turtles varied according to tissue type. The greatest values (up to 26.77 mg/kg dry weight) were in the scutes of 1 of our oldest turtles (31.5 yrs). These elevated concentrations may be due to the affinity of As to react with sulfur in the keratin of scutes, and therefore might reflect duration of exposure in long-lived turtles. Although As concentrations generally tend to decrease when moving up to higher trophic levels in a food web, our results were different. Relatively elevated concentrations reported in sediments by us and a previous study declined in plant samples as expected. Amphipod concentrations increased but then decreased again in 3 of their invertebrate predators. Arsenic concentrations in endemic leeches were extremely elevated with a mean value of 72.2 mg/kg. The mean concentration of As in turtles was 7.08 mg/kg across tissue types and was greater than the plants or invertebrates they eat, with the notable exception of leeches, which have been proposed to be part of their diet.

Arizona↗
USGS2021

Reduced quality and synchronous collapse of forage species disrupts trophic transfer during a prolonged marine heatwave

The Gulf of Alaska forage fish community includes a few key species that differ markedly in their timing of spawning, somatic growth and lipid storage, and in their migration behavior. This diversity in life history strategies facilitates resilience in marine food webs because it buffers predators against the naturally high variance in abundance of pelagic forage fish populations by decreasing the likelihood that all species will be scarce at the same time. During the prolonged North Pacific marine heatwave of 2014-2016, the availability and quality of at least three key forage species with different life history strategies were reduced simultaneously in the system. Capelin and sand lance occurrence in predator diets declined abruptly, and Prince William Sound herring spawning biomass declined to historically low levels. Biomass of euphausiids was also reduced, in part due to the loss of a cold-water species. Changes in age structure, growth, and energy content of capelin, sand lance, and herring were also associated with warming during the heatwave, but not all species responded in the same way. For example, spawning capelin grew faster and matured at a younger age but were shorter in length than usual, while sand lance in Prince William Sound experienced anomalously low growth rates and lipid storage in 2015-2016. Changes in forage fish populations had immediate impacts on predator populations in 2015-2016, when seabirds and marine mammals experienced shifts in distribution, mass mortality, and reproductive failures in the Gulf of Alaska. In contrast, copepod abundance increased on the shelf and in some coastal regions during the heatwave, suggesting that food availability was not a primary factor limiting forage fish populations at this time. The reduced quality and collapse of multiple forage fish populations reduced the efficiency of energy transfer through the middle trophic level of pelagic food webs, disrupting energy flow to piscivorous pelagic predators and causing abrupt and extreme reductions in their numbers and productivity.

Alaska↗
USGS2014

Experimental evaluation of rainbow trout Oncorhynchus mykiss predation on longnose dace Rhinichthys cataractae

Laboratory and in-stream enclosure experiments were used to determine whether rainbow trout Oncorhynchus mykiss influence survival of longnose dace Rhinichthys cataractae . In the laboratory, adult rainbow trout preyed on longnose dace in 42% of trials and juvenile rainbow trout did not prey on longnose dace during the first 6 h after rainbow trout introduction. Survival of longnose dace did not differ in the presence of adult rainbow trout previously exposed to active prey and those not previously exposed to active prey ( = 0.28, P = 0.60). In field enclosures, the number of longnose dace decreased at a faster rate in the presence of rainbow trout relative to controls within the first 72 h, but did not differ between moderate and high densities of rainbow trout ( F 2,258.9 = 3.73, P = 0.03). Additionally, longnose dace were found in 7% of rainbow trout stomachs after 72 h in enclosures. Rainbow trout acclimated to the stream for longer periods had a greater initial influence on the number of longnose dace remaining in enclosures relative to those acclimated for shorter periods regardless of rainbow trout density treatment ( F 4,148.5 = 2.50, P = 0.04). More research is needed to determine how predation rates will change in natural environments, under differing amounts of habitat and food resources and in the context of whole assemblages. However, if rainbow trout are introduced into the habitat of longnose dace, some predation on longnose dace is expected, even when rainbow trout have no previous experience with active prey.

Ecology of Freshwater Fish↗
USGS2022

Direct and indirect influences of macrophyte cover on abundance and growth of juvenile Atlantic salmon

1. The relationships between macrophytes and the physical and biological characteristics of the environments that aquatic organisms inhabit are complex. Previous studies have shown that the macrophytes, Ranunculus (subgenus Batrachium ), which are dominant in lowland chalk streams and widespread across Europe, can enhance juvenile Atlantic salmon abundance and growth to a greater degree than other physical and biological habitat characteristics. However, mechanistic understanding of how this effect might arise requires consideration of the direct and indirect relationships among habitat characteristics that are likely to be influenced by the presence of macrophyte cover. 2. We applied structural equation modelling to data collected during a 2-year in-river manipulative experiment in the River Frome (southern England, U.K.) designed to quantify the magnitude and the relative importance of direct and indirect influences of Ranunculus cover and other physical and biological variables, including water velocity, water depth, prey biomass and body size, and abundance of con- and hetero-specifics, on abundance and somatic growth of 0+ salmon. 3. Results indicated a strongly positive direct influence of Ranunculus cover on salmon abundance, as well as positive influences of Ranunculus on velocity heterogeneity and water depth that are indirectly related to decreased salmon abundance. Interestingly, there was no indication of a direct influence of Ranunculus cover on salmon growth, although Ranunculus was indirectly related to increased salmon growth through its positive influence on prey biomass, an effect mediated by velocity heterogeneity and proportion of fast velocities. 4. These findings provide novel mechanistic insights into the key role of Ranunculus in their native lowland rivers to enhance abundance and improve conditions for multiple food web components. Strategies to maintain or enhance naturally occurring Ranunculus in these rivers are therefore likely to return wide ranging ecosystem benefits, including for species of high conservation value, such as salmon. These mechanistic impacts on habitat heterogeneity and ecosystem productivity could generalise to native macrophytes in other river systems, particularly where habitat is dominated by vegetation in the absence of large substrates.

Dorset County↗
USGS2009

A shift in the dominant toxin-producing algal species in central California alters phycotoxins in food webs

In California, the toxic algal species of primary concern are the dinoflagellate Alexandrium catenella and members of the pennate diatom genus Pseudo-nitzschia, both producers of potent neurotoxins that are capable of sickening and killing marine life and humans. During the summer of 2004 in Monterey Bay, we observed a change in the taxonomic structure of the phytoplankton community-the typically diatom-dominated community shifted to a red tide, dinoflagellate-dominated community. Here we use a 6-year time series (2000-2006) to show how the abundance of the dominant harmful algal bloom (HAB) species in the Bay up to that point, Pseudo-nitzschia, significantly declined during the dinoflagellate-dominated interval, while two genera of toxic dinoflagellates, Alexandrium and Dinophysis, became the predominant toxin producers. This change represents a shift from a genus of toxin producers that typically dominates the community during a toxic bloom, to HAB taxa that are generally only minor components of the community in a toxic event. This change in the local HAB species was also reflected in the toxins present in higher trophic levels. Despite the small contribution of A. catenella to the overall phytoplankton community, the increase in the presence of this species in Monterey Bay was associated with an increase in the presence of paralytic shellfish poisoning (PSP) toxins in sentinel shellfish and clupeoid fish. This report provides the first evidence that PSP toxins are present in California's pelagic food web, as PSP toxins were detected in both northern anchovies (Engraulis mordax) and Pacific sardines (Sardinops sagax). Another interesting observation from our data is the co-occurrence of DA and PSP toxins in both planktivorous fish and sentinel shellfish. We also provide evidence, based on the statewide biotoxin monitoring program, that this increase in the frequency and abundance of PSP events related to A. catenella occurred not just in Monterey Bay, but also in other coastal regions of California. Our results demonstrate that changes in the taxonomic structure of the phytoplankton community influences the nature of the algal toxins that move through local food webs and also emphasizes the importance of monitoring for the full suite of toxic algae, rather than just one genus or species. ?? 2008 Elsevier B.V.

Harmful Algae↗
USGS2003

Difficulties in relating Cd concentrations in the predatory insect Chaoborus to those of its prey in nature

Because Chaoborus larvae take up most of their cadmium (Cd) from food, we tested the hypothesis that Cd concentrations in this insect are directly related to those in their planktonic prey. We measured Cd in Chaoborus and in Zooplankton collected from 24 eastern Canadian lakes varying widely in their Cd concentrations. Cd concentrations in the predator were not correlated with those in bulk zooplankton, whether separated into size fractions liable to be eaten by Chaoborus or not. In highly acidic lakes, Cd concentrations in Chaoborus did not respond to increases in zooplankton Cd because of either competition between H and Cd ions at Cd absorption sites in the predator's gut or differences in prey community composition between highly acidic and circumneutral lakes. Relationships between Cd in Chaoborus and in its potential prey were stronger when we used Cd concentrations for specific crustacean taxa in a mechanistic model. We conclude that predictive relationships between metal concentrations in predators and their prey are likely to be strongest if the subset of prey consumed by the predator has been characterized and if this information is used in a bioaccumulation model.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2023

Landscape diversity promotes stable food-web architectures in large rivers

Uncovering relationships between landscape diversity and species interactions is crucial for predicting how ongoing land-use change and homogenization will impact the stability and persistence of communities. However, such connections have rarely been quantified in nature. We coupled high-resolution river sonar imaging with annualized energetic food webs to quantify relationships among habitat diversity, energy flux, and trophic interaction strengths in large-river food-web modules that support the endangered Pallid Sturgeon. Our results demonstrate a clear relationship between habitat diversity and species interaction strengths, with more diverse foraging landscapes containing higher production of prey and a greater proportion of weak and potentially stabilizing interactions. Additionally, rare patches of large and relatively stable river sediments intensified these effects and further reduced interaction strengths by increasing prey diversity. Our findings highlight the importance of landscape characteristics in promoting stabilizing food-web architectures and provide direct relevance for future management of imperilled species in a simplified and rapidly changing world.

Ecology Letters↗
USGS2024

Methodology for inclusion of produced and stored carbon dioxide in the U.S. Geological Survey Federal lands greenhouse gas inventory

The U.S. Geological Survey (USGS) has developed two new carbon dioxide (CO2) emissions and sequestration accounting methods for use in future reports. The first method is a Federal lease-produced CO2 emissions calculation for an update of the report, “Federal Lands Greenhouse Gas Emissions and Sequestration in the United States.” The methodology to incorporate Federal lease CO2 production emissions into the updated report relies on CO2 sales royalty data from the Office of Natural Resources Revenue (ONRR). The end usage points for the gas include enhanced oil recovery with CO2 (CO2-EOR), food and beverage, and chemical production. CO2-EOR is the main end point for natural CO2 production in the United States; it accounted for 94% of usage in 2022 [1]. Federal lands emissions from this sector are estimated at 460 metric tons of CO2 in 2022, a very small amount relative to most other Federal lands emissions sector estimates. The second new method, planned for a separate report, is a calculation of the geologic storage of CO2 on Federal lands. The second method estimates the CO2 stored under Federal surface lands and documents Federal climate change mitigation efforts. Currently, there is no storage of CO2 at an industrial level on Federal lands, however multiple proposals and projects are planned. This method was developed on non-Federal lands datasets in an effort to prepare for when these activities on Federal lands will require accounting. National estimates for CO2 geologic storage using this method, but without a Federal lands filtering step, totaled 8.0 million metric tons (Mt) in 2022. The two methods described here are new benchmark methods in a collection of accounting procedures to document the current state of greenhouse gas emissions and their storage on Federal lands. These benchmarks can then be used to measure any subsequent changes in emissions from or carbon storage beneath Federal lands. While the magnitude of the values is currently non-existent to small, emissions mitigation goals established by decision makers indicate that these values will grow, and their documentation will take on greater value and use.

continental United States↗
USGS1995

Top-level carnivores and ecosystem effects: Questions and approaches

Top-level carnivores comprise a diverse array of taxa and occur in most natural ecosystems. This chapter considers three main questions: What are the ecological and evolutionary effects of top-level carnivores, how general are they, and under what conditions do they occur? To answer these questions one first must determine whether a food web is under top-down control, and ultimately, the species, systems, and circumstances for which top-down control exists. For systems affected by top-down forces, the cascading effect of carnivory on autotrophs is expected to vary with the order of trophic complexity. Given this conceptual framework, three more specific questions are explored. First, how general are the direct and indirect effects of top-level carnivores? Second, what is the breadth of trophic influence from the direct impact of carnivory? Broadly ranging effects are expected for systems in which (1) top-level carnivores occupy odd-numbered trophic levels and (2) the food web is strongly linked. (3) what are the evolutionary consequences of trophic cascades on species lower in the food web? These questions can best be answered via manipulative or natural experiments in which the presence or absence of carnivores varies in space or time. Natural experiments are advocated as the only practical means of addressing these questions for many species and systems, in particular those in which the key players are large and highly mobile, or those in which the manipulation of predators has legal, political, or social ramifications.

Linking Species and Ecosystems↗
USGS2013

U.S. Geological Survey ecosystems science strategy—Advancing discovery and application through collaboration

Executive Summary Ecosystem science is critical to making informed decisions about natural resources that can sustain our Nation’s economic and environmental well-being. Resource managers and policymakers are faced with countless decisions each year at local, regional, and national levels on issues as diverse as renewable and nonrenewable energy development, agriculture, forestry, water supply, and resource allocations at the urban-rural interface. The urgency for sound decisionmaking is increasing dramatically as the world is being transformed at an unprecedented pace and in uncertain directions. Environmental changes are associated with natural hazards, greenhouse gas emissions, and increasing demands for water, land, food, energy, mineral, and living resources. At risk is the Nation’s environmental capital, the goods and services provided by resilient ecosystems that are vital to the health and wellbeing of human societies. Ecosystem science—the study of systems of organisms interacting with their environment and the consequences of natural and human-induced change on these systems—is necessary to inform decisionmakers as they develop policies to adapt to these changes. This Ecosystems Science Strategy is built on a framework that includes basic and applied science. It highlights the critical roles that U.S. Geological Survey (USGS) scientists and partners can play in building scientific understanding and providing timely information to decisionmakers. The strategy underscores the connection between scientific discoveries and the application of new knowledge, and it integrates ecosystem science and decisionmaking, producing new scientific outcomes to assist resource managers and providing public benefits. We envision the USGS as a leader in integrating scientific information into decisionmaking processes that affect the Nation’s natural resources and human well-being. The USGS is uniquely positioned to play a pivotal role in ecosystem science. With its wide range of expertise, the Bureau can bring holistic, cross-scale, interdisciplinary capabilities to the design and conduct of monitoring, research, and modeling and to new technologies for data collection, management, and visualization. Collectively, these capabilities can be used to reveal ecological patterns and processes, explain how and why ecosystems change, and forecast change over different spatial and temporal scales. USGS science can provide managers with options and decision-support tools to use resources sustainably. The USGS has long-standing, collaborative relationships with the Department of the Interior (DOI) and other partners in the natural sciences, in both conducting science and applying the results. The USGS engages these partners in cooperative investigations that otherwise would lack the necessary support or be too expensive for a single bureau to conduct. The heart of this strategy is a framework for USGS ecosystems science that focuses on five long-term goals, which are seen as interconnected components that reinforce our vision of the USGS providing science that is at the forefront of decisionmaking: Improve understanding of ecosystem structure, function, and processes. The focus for this goal is an understanding of how ecosystems work, including the dynamics of species, their populations, interactions, and genetics, and how they change across spatial and temporal scales. Advance understanding of how drivers influence ecosystem change. The challenges here are explaining the drivers of ecosystem change, their spatio-temporal patterns, their uncertainties and interactions, and their influence on ecosystem processes and dynamics. Improve understanding of the services that ecosystems provide to society. Here the emphasis is on the measurement of environmental capital and ecosystem services, and the identification of sources and patterns of change in space and time. Develop tools, technologies, and capacities to inform decisionmaking about ecosystems. This includes developing new technologies and approaches for conducting applications-oriented ecosystem science. A principal challenge will be how to quantify uncertainty and incorporate it in decision analysis. Apply science to enhance strategies for management, conservation, and restoration of ecosystems. These challenges include development of novel approaches to monitoring, assessment, and restoration of ecosystems; new methods to address species of concern and communities at risk; and innovations in decision analysis and support to address imminent ecosystem changes or those that are underway. Closely integrated with the five goals are four strategic approaches that provide the path forward for the USGS Ecosystems Mission Area. These approaches cross-cut all of the goals and are seen as essential to the implementation of this strategy: Assess information needs for ecosystem science through enhanced partnerships. Work with the DOI and other agencies and institutions to identify, design, and implement priority decision-driven ecological research. Promote the use of interdisciplinary ecosystem science. Design and conduct interdisciplinary process-oriented research in ecosystem science. Enhance modeling and forecasting. Build models to forecast ecosystem change, assess future management scenarios, and reduce uncertainties through an adaptive learning process. Support decisionmaking. Use quantitative approaches to assess the vulnerabilities of ecosystems, habitats, and species, and evaluate strategies for adaptation, restoration, and sustainable management. Following the four strategic approaches are a set of proposed actions that represent a sampling of specific USGS activities that align with this strategy and that address the Nation’s most pressing environmental needs. The strategy emphasizes coordination of activities across the USGS mission areas pursuant to these goals. Ecosystem science is inherently interdisciplinary and requires a broad perspective that incorporates the biological and physical sciences, climate science, information technology, and scientific capacity in mission areas across the Bureau. With its emphasis on coordination, this strategy can provide a critical underpinning for integrated science efforts with scientists from multiple mission areas of the USGS working together. Of course, the USGS will continue to conduct discipline-specific and interdisciplinary investigations, and both will continue to be vital parts of the ecosystem science portfolio. Finally, the strategy stresses the importance of coordination with other Federal agencies and organizations in the natural resources community. The USGS collaborates with resource agencies in the DOI and other organizations throughout the world to meet societal needs for species and ecosystem management. Working with these agencies and organizations, the USGS will play a key role in guiding sound decisionmaking during the next decade by advancing the scientific foundation for sustaining the natural resources that diverse, productive, resilient ecosystems provide.

Circular↗
USGS2021

Regional occurrence of aqueous tungsten and relations with antimony, arsenic and molybdenum concentrations (Sardinia, Italy)

T ungsten (W) is rarely found in natural waters, yet it can be introduced into the food chain and cause potentially toxic effects. Uptake of W by plants and vegetables, or trace presence of W in drinking water are possible vectors for ingestion of W by humans. The latter is recognized as a possible cause of lymphatic leukemia. Increased uses of W might result in a degradation of water resources, with attendant adverse effects on biota and human health. Therefore, this study was aimed at investigating regional occurrence and speciation of W in aquatic systems in Sardinia, Italy, factors affecting W mobility and possible relations with other oxyanion-forming trace elements such as Sb, As and Mo. Although our results are specifically from Sardinia, the implications are broader and should prompt future studies in other areas with known high W concentrations. A total of 350 sample sites are reported here, including surface waters, groundwaters, mine drainages, thermal waters and local seawater. The waters were analyzed for major and trace components, including W, Sb, As and Mo. The waters showed a variety of major chemical compositions and W concentrations. High concentrations of W were found in some mine waters and drainages from slag heaps, with W, Sb and As up to 140, 5000 and 800 μg L −1 , respectively. The highest concentrations of W occurred under slightly alkaline pH and oxygenated conditions, and were likely due to the dissolution of scheelite [CaWO 4 ] hosted in materials with which the water came into contact. High W concentrations also were observed in thermal waters, under alkaline pH and reducing conditions, and sometimes coincided with relatively high concentrations either of As or Mo. Previous studies of W geochemistry have focused on WO 4 2− as the major dissolved form of W. For this study, we have augmented the thermodynamic database in PHREEQC to include possible formation of many other W-bearing complexes gleaned from the literature. The results of the speciation calculations with the newly added complexation reactions shows that the neutral species CaWO 4 ° and MgWO 4 ° are particularly dominant in most W-bearing waters and lead to undersaturation with respect to scheelite and other W-bearing minerals. Assessing W contamination in water systems and establishing W limits in drinking water may prevent potential adverse effects of W on human and ecosystem health.

Sardinia↗
USGS2026

Seasonal environmental conditions and river morphology shape summer phytoplankton communities

1. Phytoplankton form the base of large river food webs but there are limited studies on the nature and drivers of communities over longer time scales. Further, climate change is projected to favor taxa associated with harmful algal blooms, but our knowledge of the timing, locations, and drivers of cyanobacteria in rivers lags that of lakes and marine environments. 2. We used a summer phytoplankton community dataset collected from 2010-2020 across main channel, side channel and backwater areas in the La Grange reach of the Illinois River to assess: 1) How much do summer phytoplankton communities across diverse aquatic areas within a large river vary from year to year?, 2) What environmental conditions are associated with that variation?, and 3) Do cyanobacteria respond differently than the full phytoplankton community? 3. We found greater differences in phytoplankton communities across years than among aquatic areas. Further, we showed that annual variation in phytoplankton communities was synchronous among taxa in the same aquatic area, rather than specific to each taxonomic group or taxa-area combination. After accounting for this spatial variation in annual dynamics, phytoplankton reflected river conditions across seasons, responding positively to summer total phosphorus and invasive carp abundance and negatively to winter discharge and spring silica to nitrogen ratio. Annual variation in cyanobacteria was similarly distinct among main channel, side channel and backwater areas but was best explained by the ratio of summer air temperature to discharge, representing conditions that favored growth over transport. 4. These results show that annual variation in summer phytoplankton and cyanobacterial communities both reflected the spatial diversity of the river landscape and responded to conditions that occurred at different spatial and temporal scales. Further, in this highly modified river basin, we showed that a mix of anthropogenic pressures including eutrophication, invasive species, and potential changes to winter and spring conditions affected the phytoplankton communities present in the summer. Thus, when evaluating long-term change and the potential for harmful algal blooms in rivers it is important to consider spatial diversity of phytoplankton communities, how their sensitivity to environmental change may vary across the river landscape, and the suite of human modifications acting on those communities.

Illinois↗
USGS2010

Mercury in Indiana watersheds: Retrospective for 2001–2006

Information about total mercury and methylmercury concentrations in water samples and mercury concentrations in fish-tissue samples was summarized for 26 watersheds in Indiana that drain most of the land area of the State. Mercury levels were interpreted with information on streamflow, atmospheric mercury deposition, mercury emissions to the atmosphere, mercury in wastewater, and landscape characteristics. Unfiltered total mercury concentrations in 411 water samples from streams in the 26 watersheds had a median of 2.32 nanograms per liter (ng/L) and a maximum of 28.2 ng/L. When these concentrations were compared to Indiana water-quality criteria for mercury, 5.4 percent exceeded the 12-ng/L chronic-aquatic criterion, 59 percent exceeded the 1.8-ng/L Great Lakes human-health criterion, and 72.5 percent exceeded the 1.3-ng/L Great Lakes wildlife criterion. Mercury concentrations in water were related to streamflow, and the highest mercury concentrations were associated with the highest streamflows. On average, 67 percent of total mercury in streams was in a particulate form, and particulate mercury concentrations were significantly lower downstream from dams than at monitoring stations not affected by dams. Methylmercury is the organic fraction of total mercury and is the form of mercury that accumulates and magnifies in food chains. It is made from inorganic mercury by natural processes under specific conditions. Unfiltered methylmercury concentrations in 411 water samples had a median of 0.10 ng/L and a maximum of 0.66 ng/L. Methylmercury was a median 3.7 percent and maximum 64.8 percent of the total mercury in 252 samples for which methylmercury was reported. The percentages of methylmercury in water samples were significantly higher downstream from dams than at other monitoring stations. Nearly all of the total mercury detected in fish tissue was assumed to be methylmercury. Fish-tissue samples from the 26 watersheds had wet-weight mercury concentrations that exceeded the 0.3 milligram per kilogram (mg/kg) U.S. Environmental Protection Agency (USEPA) methylmercury criterion in 12.4 percent of the 1,731 samples. The median wet-weight concentration in the fish-tissue samples was 0.13 mg/kg, and the maximum was 1.07 mg/kg. A coarse-scale analysis of all fish-tissue data in each watershed and a fine-scale analysis of data within 5 kilometers (km) of the downstream end of each watershed showed similar results overall. Mercury concentrations in fish-tissue samples were highest in the White River watershed in southern Indiana and the Fall Creek watershed in central Indiana. In fish-tissue samples within 5 km of the downstream end of a watershed, the USEPA methylmercury criterion was exceeded by 45 percent of mercury concentrations from the White River watershed and 40 percent of the mercury concentration from the Fall Creek watershed. A clear relation between mercury concentrations in fish-tissue samples and methylmercury concentrations in water was not observed in the data from watersheds in Indiana. Average annual atmospheric mercury wet-deposition rates were mapped with data at 156 locations in Indiana and four surrounding states for 2001–2006. These maps revealed an area in southeastern Indiana with high mercury wet-deposition rates—from 15 to 19 micrograms per square meter per year (µg/m 2 /yr). Annual atmospheric mercury dry-deposition rates were estimated with an inferential method by using concentrations of mercury species in air samples at three locations in Indiana. Mercury dry deposition-rates were 5.6 to 13.6 µg/m 2 /yr and were 0.49 to 1.4 times mercury wet-deposition rates. Total mercury concentrations were detected in 96 percent of 402 samples of wastewater effluent from 50 publicly owned treatment works in the watersheds; the median concentration was 3.0 ng/L, and the maximum was 88 ng/L. When these concentrations were compared to Indiana water-quality criteria for mercury, 12 percent exceeded the 12-ng/L chronic-aquatic criterion, 68 percent exceeded the 1.8-ng/L Great Lakes human-health criterion, and 81 percent exceeded the 1.3-ng/L Great Lakes wildlife criterion. Annual stream mercury yields were calculated with a model by using the mercury concentrations in water samples and daily average streamflows for 2002–2006, normalized to the watershed drainage areas. The average annual total mercury stream yields ranged from 0.73 to 45.2 µg/m 2 /yr and were highest in two White River watersheds in central Indiana. Median methylmercury stream yield was 1.9 percent of the median total mercury stream yield. In most watersheds, average annual stream yields of total mercury were a fraction of the combined average annual atmospheric mercury wet-deposition and estimated annual dry-deposition loading rates, indicating that much of the stream mercury was attributable to atmospheric deposition. In two watersheds, average annual stream yields of total mercury were approximately twice the atmospheric mercury loading, indicating that some of the stream mercury apparently was not attributable to atmospheric deposition. Rather, some of the stream mercury yield potentially was contributed by mercury in wastewater discharges. Land-cover type corresponded with the mercury levels in three watersheds: (1) A watershed of the White River in central Indiana with a high percentage of urban land cover had some of the highest total mercury concentrations and stream mercury yields. The urban land cover and numerous permitted wastewater outfalls with mercury in treated effluent potentially contributed mercury to this watershed. (2) A monitoring station on the Maumee River in northeastern Indiana, downstream from a large area of urban land cover, recorded the highest stream mercury concentrations. The urban land cover and mercury detected in treated effluent potentially contributed to the high mercury concentrations at this station. (3) A watershed of the Patoka River in southern Indiana with a high percentage of forest land cover had the highest atmospheric mercury dry-deposition rate. The high dry-deposition rate from the forest land cover potentially contributed to the high mercury concentrations in this watershed. From a retrospective view, mercury concentrations in Indiana watersheds routinely exceeded criteria protective of humans and commonly exceeded criteria protective of wildlife. Atmospheric mercury wet deposition was a predominant factor, but not the single factor, affecting mercury in Indiana watersheds. Mercury in wastewater discharges and atmospheric mercury dry deposition apparently contributed a substantial part of the mercury yield from some watersheds. Dams and impoundments increased the percentage of methylmercury in downstream waters. Long-term monitoring of mercury in wet and dry atmospheric deposition, and in streams and reservoirs, coordinated with monitoring of mercury in fish, will be needed to detect whether mercury levels in Indiana watersheds change in the future.

Indiana↗
USGS2012

The U.S. Geological Survey Ecosystem Science Strategy, 2012-2022 - Advancing discovery and application through collaboration

Ecosystem science is critical to making informed decisions about natural resources that can sustain our Nation’s economic and environmental well-being. Resource managers and policy-makers are faced with countless decisions each year at local, state, tribal, territorial, and national levels on issues as diverse as renewable and non-renewable energy development, agriculture, forestry, water supply, and resource allocations at the urban-rural interface. The urgency for sound decision-making is increasing dramatically as the world is being transformed at an unprecedented pace and in uncertain directions. Environmental changes are associated with natural hazards, greenhouse gas emissions, and increasing demands for water, land, food, energy, mineral, and living resources. At risk is the Nation’s environmental capital, the goods and services provided by resilient ecosystems that are vital to the health and well-being of human societies. Ecosystem science—the study of systems of organisms interacting with their environment and the consequences of natural and human-induced change on these systems—is necessary to inform decision-makers as they develop policies to adapt to these changes. This Ecosystems Science Strategy is built on a framework that includes basic and applied science. It highlights the critical roles that USGS scientists and partners can play in building scientific understanding and providing timely information to decision-makers. The strategy underscores the connection between scientific discoveries and the application of new knowledge. The strategy integrates ecosystem science and decision-making, producing new scientific outcomes to assist resource managers and providing public benefits. The USGS is uniquely positioned to play an important role in ecosystem science. With its wide range of expertise, the agency can bring holistic, cross-scale, interdisciplinary capabilities to the design and conduct of monitoring, research, and modeling and to new technologies for data collection, management, and visualization. Collectively, these capabilities can be used to reveal ecological patterns and processes, explain how and why ecosystems change, and forecast change over different spatial and temporal scales. USGS science can provide managers with options and decision-support tools to use resources sustainably. The USGS has long-standing, collaborative relationships with the DOI and other partners in the natural sciences, in both conducting science and its application. The USGS engages these partners in cooperative investigations that otherwise would lack the necessary support or be too expensive for a single bureau to conduct. The heart of this strategy is a framework and vision for USGS ecosystems science that focuses on five long-term goals, which are seen as interconnected and reinforcing components: • Improve understanding of ecosystem structure, function, and processes. The focus for this goal is an understanding of how ecosystems work, including the dynamics of species, their populations, interactions, and genetics, and how they change across spatial and temporal scales. • Advance understanding of how drivers influence ecosystem change. The challenges here are explaining the drivers of ecosystem change, their spatio-temporal patterns, their uncertainties and interactions, and their influence on ecosystem processes and dynamics. • Improve understanding of the services that ecosystems provide to society. Here the emphasis is on the measurement of environmental capital and ecosystem services, and the identification of sources and patterns of change in space and time. • Develop tools, technologies, and capacities to inform decision-making about ecosystems. This includes developing new technologies and approaches for conducting applications-oriented ecosystem science. A principal challenge will be how to quantify uncertainty and incorporate it in decision analysis. • Apply science to enhance strategies for management, conservation, and restoration of ecosystems. These challenges include development of novel approaches to monitoring, assessment, and restoration of ecosystems; new methods to address species of concern and communities at risk; and innovations in decision analysis and support to address imminent ecosystem changes or those that are underway. Closely integrated with the five goals are four strategic approaches that provide the path forward for the USGS Ecosystems Mission Area. These approaches cross-cut all of the goals and are seen as essential to the implementation of this strategy: • Assess information needs for ecosystem science through enhanced partnerships. Work with the DOI and other agencies and institutions to identify, design, and implement priority decision-driven ecological research. • Promote the use of interdisciplinary ecosystem science. Design and conduct interdisciplinary process-oriented research in ecosystem science. • Enhance modeling and forecasting. Build models to forecast ecosystem change, assess future management scenarios, and reduce uncertainties through an adaptive learning process. • Support decision-making. Use quantitative approaches to assess the vulnerabilities of ecosystems, habitats, and species, and evaluate strategies for adaptation, restoration, and sustainable management. Following the strategic approaches are a set of proposed actions that represent a sampling of specific activities that align with this strategy and that address the Nation’s most pressing environmental needs. The strategy emphasizes coordination of activities across the USGS mission areas pursuant to these goals. Ecosystem science is inherently interdisciplinary and requires a broad perspective that incorporates the biological and physical sciences, climate science, information technology, and scientific capacity in mission areas across the Bureau. With its emphasis on coordination, this strategy can provide a critical underpinning for integrated science efforts with scientists from multiple mission areas of the USGS working together. Of course, the USGS will continue to conduct both discipline-specific and interdisciplinary investigations, and both will continue to be vital parts of the ecosystem science portfolio. Finally, the strategy stresses the importance of coordination with other Federal agencies and organizations in the natural resources community. The USGS collaborates with resource agencies in the DOI and other organizations throughout the world to meet societal needs for species and ecosystem management. Working with these agencies and organizations, the USGS will play a key role over the next decade in advancing the scientific foundation for sustaining the natural resources that diverse, productive, resilient ecosystems provide.

Open-File Report↗
USGS2005

Effects of forest structure and composition on food availability for Varecia variegata at Ranomafana National Park, Madagascar

We present a summary of a long-term field study that examined the effects of forest disturbance on the availability of palatable fruit and its utilization by V. variegata. Forest structure and tree species composition were measured in three adjacent study areas, with different histories of disturbance, in Ranomafana National Park (RNP), Madagascar. V. variegata abundance was monitored by frequent encounters with resident groups and periodic censuses conducted along trails. Finally, the abundance of mature fruit in species used by V. variegata was scored monthly at representative trees at several locations. V. variegata abundance was most consistent in the least anthropogenically disturbed site, while no established lemur groups were observed in the heavily logged site for over a decade post-harvest. Lemur abundance was variable in the selectively logged site. The presence of select food trees, particularly specimens with voluminous crowns capable of producing abundant fruit crops, appears to be key to the establishment and expansion of V variegata groups. Our analysis of year-long fruit utilization revealed a high degree of preference for several species of trees. Two species exhibited mature fruit in a low percentage of stems but were available for a protracted period of time, while two additional species showed high intraspecific fruiting synchrony and were available for a shorter period of time. These contrasting phenologies, rather than the individual tree species, may be most important to V. variegata due to their coincident timing of fruit maturation with key lemur life-history events. Any disturbance-natural or anthropogenic-that disrupts the phenology cycles of food trees has the potential to impact lemur abundance and dispersion. Intense disturbances, such as heavy logging or severe cyclones, have long-lasting impacts on fruit production, while selective logging or moderate cyclonic windthrow cause more transient impacts. V. variegata is adapted to deal with an intrinsically erratic food supply by virtue of its reproductive biology and social behavior.

American Journal of Primatology↗
USGS2013

U.S. Geological Survey core science systems strategy: Characterizing, synthesizing, and understanding the critical zone through a modular science framework

Executive Summary Core Science Systems is a new mission of the U.S. Geological Survey (USGS) that resulted from the 2007 Science Strategy, “Facing Tomorrow’s Challenges: U.S. Geological Survey Science in the Decade 2007–2017.” This report describes the Core Science Systems vision and outlines a strategy to facilitate integrated characterization and understanding of the complex Earth system. The vision and suggested actions are bold and far-reaching, describing a conceptual model and framework to enhance the ability of the USGS to bring its core strengths to bear on pressing societal problems through data integration and scientific synthesis across the breadth of science. The context of this report is inspired by a direction set forth in the 2007 Science Strategy. Specifically, ecosystem-based approaches provide the underpinnings for essentially all science themes that define the USGS. Every point on Earth falls within a specific ecosystem where data, other information assets, and the expertise of USGS and its many partners can be employed to quantitatively understand how that ecosystem functions and how it responds to natural and anthropogenic disturbances. Every benefit society obtains from the planet— food, water, raw materials to build infrastructure, homes and automobiles, fuel to heat homes and cities, and many others— are derived from or affect ecosystems. The vision for Core Science Systems builds on core strengths of the USGS in characterizing and understanding complex Earth and biological systems through research, modeling, mapping, and the production of high quality data on the Nation’s natural resource infrastructure. Together, these research activities provide a foundation for ecosystem-based approaches through geologic mapping, topographic mapping, and biodiversity mapping. The vision describes a framework founded on these core mapping strengths that makes it easier for USGS scientists to discover critical information, share and publish results, and identify potential collaborations that transcend all USGS missions. The framework is designed to improve the efficiency of scientific work within USGS by establishing a means to preserve and recall data for future applications, organizing existing scientific knowledge and data to facilitate new use of older information, and establishing a future workflow that naturally integrates new data, applications, and other science products to make interdisciplinary research easier and more efficient. Given the increasing need for integrated data and interdisciplinary approaches to solve modern problems, leadership by the Core Science Systems mission will facilitate problem solving by all USGS missions in ways not formerly possible. The report lays out a strategy to achieve this vision through three goals with accompanying objectives and actions. The first goal builds on and enhances the strengths of the Core Science Systems mission in characterizing and understanding the Earth system from the geologic framework to the topographic characteristics of the land surface and biodiversity across the Nation. The second goal enhances and develops new strengths in computer and information science to make it easier for USGS scientists to discover data and models, share and publish results, and discover connections between scientific information and knowledge. The third goal brings additional focus to research and development methods to address complex issues affecting society that require integration of knowledge and new methods for synthesizing scientific information. Collectively, the report lays out a strategy to create a seamless connection between all USGS activities to accelerate and make USGS science more efficient by fully integrating disciplinary expertise within a new and evolving science paradigm for a changing world in the 21st century.

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