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ISA NOxSOxPM Ecology (2018)

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Journal Article
Journal Article

Critical loads of atmospheric N deposition for phytoplankton nutrient limitation shifts in western U.S. mountain lakes

Authors: Williams, JJ; Lynch, JA; Saros, JE; Labou, SG (2017) Ecosphere 8:e01955. HERO ID: 4034559

[Less] In many oligotrophic mountain lakes, anthropogenic atmospheric nitrogen (N) deposition has increased . . . [More] In many oligotrophic mountain lakes, anthropogenic atmospheric nitrogen (N) deposition has increased concentrations of N, a key limiting nutrient, and thereby shifted phytoplankton biomass growth from N limitation to P limitation. In the western United States, the critical load N deposition rate for these shifts has not been quantified. We synthesized existing mountain lake chemistry, nutrient limitation bioassay, and N deposition data to estimate N critical loads for shifts from N to P limitation of phytoplankton biomass growth. Data from bioassays in 47 mountain lakes were used to define biological (RR-N/RR-P = 1) and chemical (NO3, DIN, DIN:TP) thresholds above which biomass P limitation is more likely than N limitation. Logistic regression was used to calculate critical loads as the total N deposition rate with >50% probability of exceeding biological or chemical thresholds, and thus where P limitation is more likely than N limitation. Logistic regression models were developed with N deposition as the only predictor and with both N deposition and watershed characteristics as predictors. Logistic model performance was evaluated by comparing predicted and observed chemical threshold exceedances in 108 mountain lakes. Across models, estimated critical loads ranged from 2.8 to 5.2 kg total N·ha−1·yr−1. The best-performing model was a univariate logistic model predicting NO3 threshold exceedance, with N deposition as the only predictor. This model yielded a critical load of 4.1 kg total N·ha−1·yr−1 and accurately predicted NO3 threshold exceedance in 69% of lakes. We applied this critical load to an independent sample of 385 mountain lakes with NO3 data to estimate the frequency it would fail to predict a limitation shift—cases where the NO3 threshold for biomass shifts was exceeded, but the critical load was not. The false-negative rate was 13% across the western United States, but was higher (22%) in the Sierras. Performance analyses suggest a 2.0 kg total N·ha−1·yr−1 critical load may avoid false negatives entirely. Critical loads presented here can be used to assess N deposition impacts on western U.S. mountain lakes, and associated performance information can be used to consider if presented critical loads are adequate for specific management applications.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Traceable measurements and calibration: a primer on uncertainty analysis

Authors: Csavina, J; Roberti, JA; Taylor, JR; Loescher, HW (2017) Ecosphere 8. HERO ID: 4284796

[Less] Describing the quality of measurements is necessary to understand the level of confidence in any observation. . . . [More] Describing the quality of measurements is necessary to understand the level of confidence in any observation. Accuracy, precision, trueness, repeatability, reproducibility, and uncertainty are all used to describe quality of measurement, but the terms are inconsistently defined and measured and thus easily misunderstood. One purpose of quality parameters is for the comparison of observations, but when dissimilar methods for estimating quality terms are utilized, a comparison is misrepresented. A standardized approach to estimating uncertainty provides a basis for meeting measurement requirements and providing a level of confidence for observations. Here, we show the approach used by the National Ecological Observatory Network to estimate uncertainty of the calibration processes and measurements illustrated with an example of uncertainty assessment on a temperature sensor. Detailing the approach for uncertainty assessment provides the transparency necessary for network science and allows for the approach to be adopted in the scientific community. Reporting uncertainty with all measurements needs to become consistent and commonplace across disciplines.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Evaluation of atmospheric nitrogen deposition model performance in the context of US critical load assessments

Authors: Williams, JJ; Chung, SH; Johansen, AM; Lamb, BK; Vaughan, JK; Beutel, M (2017) Atmospheric Environment 150:244-255. HERO ID: 3605775

[Less] Air quality models are widely used to estimate pollutant deposition rates and thereby calculate critical . . . [More] Air quality models are widely used to estimate pollutant deposition rates and thereby calculate critical loads and critical load exceedances (model deposition > critical load). However, model operational performance is not always quantified specifically to inform these applications, We developed a performance assessment approach designed to inform critical load and exceedance calculations, and applied it to the Pacific Northwest region of the U.S. We quantified wet inorganic N deposition performance of several widely-used air quality models, including five different Community Multiscale Air Quality Model (CMAQ) simulations, the Tdep model, and 'PRISM x NTN' model. Modeled wet inorganic N deposition estimates were compared to wet inorganic N deposition measurements at 16 National Trends Network (NTN) monitoring sites, and to annual bulk inorganic N deposition measurements at Mount Rainier National Park. Model bias (model observed) and error (vertical bar model - observed vertical bar) were expressed as a percentage of regional critical load values for diatoms and lichens. This novel approach demonstrated that wet inorganic N deposition bias in the Pacific Northwest approached or exceeded 100% of regional diatom and lichen critical load values at several individual monitoring sites, and approached or exceeded 50% of critical loads when averaged regionally. Even models that adjusted deposition estimates based on deposition measurements to reduce bias or that spatially-interpolated measurement data, had bias that approached or exceeded critical loads at some locations. While wet inorganic N deposition model bias is only one source of uncertainty that can affect critical load and exceedance calculations, results demonstrate expressing bias as a percentage of critical loads at a spatial scale consistent with calculations may be a useful exercise for those performing calculations. It may help decide if model performance is adequate for a particular calculation, help assess confidence in calculation results, and highlight cases where a non-deterministic approach may be needed. (C) 2016 Elsevier Ltd. All rights reserved.

Journal Article
Journal Article

Nitrogen-induced terrestrial eutrophication: Cascading effects and impacts on ecosystem services

Authors: Clark, CM; Bell, MD; Boyd, JW; Compton, JE; Davidson, EA; Davis, C; Fenn, ME; Geiser, L; Jones, L; Blett, TF (2017) Ecosphere 8:e01877. HERO ID: 4135271

[Less] Human activity has significantly increased the deposition of nitrogen (N) on terrestrial ecosystems . . . [More] Human activity has significantly increased the deposition of nitrogen (N) on terrestrial ecosystems over pre-industrial levels leading to a multitude of effects including losses of biodiversity, changes in ecosystem functioning, and impacts on human well-being. It is challenging to explicitly link the level of deposition on an ecosystem to the cascade of ecological effects triggered and ecosystem services affected, because of the multitude of possible pathways in the N cascade. To address this challenge, we report on the activities of an expert workshop to synthesize information on N-induced terrestrial eutrophication from the published literature and to link critical load exceedances with human beneficiaries by using the STressor- Ecological Production function final ecosystem Services Framework and the Final Ecosystem Goods and Services Classification System (FEGS-CS). We found 21 N critical loads were triggered by N deposition (ranging from 2 to 39 kg N.ha(-1),yr(-1)), which cascaded to distinct beneficiary types through 582 individual pathways in the five ecoregions examined (Eastern Temperate Forests, Marine West Coast Forests, Northwestern Forested Mountains, North American Deserts, Mediterranean California). These exceedances ultimately affected 66 FEGS across a range of final ecosystem service categories (21 categories, e.g., changes in timber production, fire regimes, and native plant and animal communities) and 198 regional human beneficiaries of different types. Several different biological indicators were triggered in different ecosystems, including grasses and/or forbs (33% of all pathways), mycorrhizal communities (22%), tree species (21%), and lichen biodiversity (11%). Ecoregions with higher deposition rates for longer periods tended to have more numerous and varied ecological impacts (e.g., Eastern Temperate Forests, eight biological indicators) as opposed to other ecoregions (e.g., North American Deserts and Marine West Coast Forests each with one biological indicator). Nonetheless, although ecoregions differed by ecological effects from terrestrial eutrophication, the number of FEGS and beneficiaries impacted was similar across ecoregions. We found that terrestrial eutrophication affected all ecosystems examined, demonstrating the widespread nature of terrestrial eutrophication nationally. These results highlight which people and ecosystems are most affected according to present knowledge, and identify key uncertainties and knowledge gaps to be filled by future research.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

A framework to quantify the strength of ecological links between an environmental stressor and final ecosystem services

Authors: Bell, MD; Phelan, J; Blett, TF; Landers, D; Nahlik, AM; Van Houtven, G; Davis, C; Clark, CM; Hewitt, J (2017) Ecosphere 8. HERO ID: 3840532

[Less] Anthropogenic stressors such as climate change, increased fire frequency, and pollution drive shifts . . . [More] Anthropogenic stressors such as climate change, increased fire frequency, and pollution drive shifts in ecosystem function and resilience. Scientists generally rely on biological indicators of these stressors to signal that ecosystem conditions have been altered. However, these biological indicators are not always capable of being directly related to ecosystem components that provide benefits to humans and/or can be used to evaluate the cost-benefit of a change in health of the component (ecosystem services). Therefore, we developed the STEPS (Stressor-Ecological Production function-final ecosystem Services) Framework to link changes in a biological indicator of a stressor to final ecosystem services. The STEPS Framework produces "chains" of ecological components that explore the breadth of impacts resulting from the change in a stressor. Chains are comprised of the biological indicator, the ecological production function (EPF, which uses ecological components to link the biological indicator to a final ecosystem service), and the user group who directly uses, appreciates, or values the component. The framework uses a qualitative score (high, medium, low) to describe the strength of science (SOS) for the relationship between each component in the EPF. We tested the STEPS Framework within a workshop setting using the exceedance of critical loads of air pollution as a model stressor and the Final Ecosystem Goods and Services Classification System (FEGS-CS) to describe final ecosystem services. We identified chains for four modes of ecological response to deposition: aquatic acidification, aquatic eutrophication, terrestrial acidification, and terrestrial eutrophication. The workshop participants identified 183 unique EPFs linking a change in a biological indicator to a FEGS; when accounting for the multiple beneficiaries, we ended with 1104 chains. The SOS scores were effective in identifying chains with the highest confidence ranking as well as those where more research is needed. The STEPS Framework could be adapted to any system in which a stressor is modifying a biological component. The results of the analysis can be used by the social science community to apply valuation measures to multiple or selected chains, providing a comprehensive analysis of the effects of anthropogenic stressors on measures of human well-being.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Spatial variation of atmospheric nitrogen deposition and critical loads for aquatic ecosystems in the Greater Yellowstone Area

Authors: Nanus, L; Mcmurray, JA; Clow, DW; Saros, JE; Blett, T; Gurdak, JJ (2017) Environmental Pollution 223:644-656. HERO ID: 3603495

[Less] Current and historic atmospheric nitrogen (N) deposition has impacted aquatic ecosystems in the Greater . . . [More] Current and historic atmospheric nitrogen (N) deposition has impacted aquatic ecosystems in the Greater Yellowstone Area (GYA). Understanding the spatial variation in total atmospheric deposition (wet + dry) of N is needed to estimate air pollution deposition critical loads for sensitive aquatic ecosystems. This is particularly important for areas that have an increasing contribution of ammonia dry deposition to total N (TN), such as the GYA. High resolution geostatistical models and maps of TN deposition (wet + dry) were developed using a variety of techniques including ordinary kriging in a geographic information system, to evaluate spatial variability and identify areas of elevated loading of pollutants for the GYA. TN deposition estimates in the GYA range from <1.4 to 7.5 kg N ha(-1) yr(-1) and show greater variability than wet inorganic N deposition. Critical loads of TN deposition (CLTNdep) for nutrient enrichment in aquatic ecosystems range from less than 1.5 ± 1.0 kg N ha(-1) yr(-1) to over 4.0 ± 1.0 kg N ha(-1) yr(-1) and variability is controlled by differences in basin characteristics. The lowest CLTNdep estimates occurred in high elevation basins within GYA Wilderness boundaries. TN deposition maps were used to identify critical load exceedances for aquatic ecosystems. Estimated CLTNdep exceedances for the GYA range from 17% to 48% depending on the surface water nitrate (NO3(-)) threshold. Based on a NO3(-) threshold of 1.0 μmol L(-1), TN deposition exceeds CLTNdep in approximately 30% of the GYA. These predictive models and maps can be used to help identify and protect sensitive ecosystems that may be impacted by excess atmospheric N deposition.

Technical Report
Technical Report

National lakes assessment 2012: A collaborative survey of lakes in the United States

Author: U.S. EPA (2016) (EPA 841-R-16-113). Washington, D.C.: U.S. Environmental Protection Agency. [EPA Report] HERO ID: 3980934

[Less] Lakes and reservoirs provide many environmental, economic, and public health benefits. We use lakes . . . [More] Lakes and reservoirs provide many environmental, economic, and public health benefits. We use lakes for drinking water, energy production, food, and recreation, while fish, birds, and other wildlife rely on them for habitat and survival. In the National Lakes Assessment (NLA), the U.S. Environmental Protection Agency (EPA) and its partners surveyed a wide array of lakes representative of those found in the U.S., from small ponds and prairie potholes to large lakes and reservoirs.

The National Lakes Assessment 2012: A Collaborative Survey of the Lakes in the United States presents the results of a second evaluation of the biological, chemical, physical, and recreational condition of lakes in the United States, the first having been conducted in 2007. During spring and summer of 2012, 89 field crews sampled 1,038 lakes across the country. Each field crew used consistent procedures to sample benthic macroinvertebrates (e.g., insect larvae, snails, and clams), zooplankton (small animals in the water column), algal toxins, atrazine, and nutrients and to observe near-shore habitat so that results could be compared across the country. These measured values were compared to NLA benchmarks, which are points of reference used to determine the proportion of lakes that are relatively high quality (least disturbed), medium quality (moderately disturbed), and degraded (most disturbed) in condition.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Nitrogen pollution is linked to US listed species declines

Authors: Hernández, DL; Vallano, DM; Zavaleta, ES; Tzankova, Z; Pasari, JR; Weiss, S; Selmants, PC; Morozumi, C (2016) BioScience 66:213-222. HERO ID: 3114292

[Less] Nitrogen (N) pollution is increasingly recognized as a threat to biodiversity. However, our understanding . . . [More] Nitrogen (N) pollution is increasingly recognized as a threat to biodiversity. However, our understanding of how N is affecting vulnerable species across taxa and broad spatial scales is limited. We surveyed approximately 1400 species in the continental United States listed as candidate, threatened, or endangered under the US Endangered Species Act (ESA) to assess the extent of recognized N-pollution effects on biodiversity in both terrestrial and aquatic ecosystems. We found 78 federally listed species recognized as affected by N pollution. To illustrate the complexity of tracing N impacts on listed species, we describe an interdisciplinary case study that addressed the threat of N pollution to California Bay Area serpentine grasslands. We demonstrate that N pollution has affected threatened species via multiple pathways and argue that existing legal and policy regulations can be applied to address the biodiversity consequences of N pollution in conjunction with scientific evidence tracing N impact pathways.

Technical Report
Technical Report

National wetland condition assessment 2011: A collaborative survey of the nation's wetlands

Author: U.S. EPA (2016) (1-105). (EPA-843-R-15-005). Washington, DC: U.S. Environmental Protection Agency. HERO ID: 3230061


Technical Report
Technical Report

Integrated science assessment (ISA) for sulfur oxides – health criteria (Second external review draft)

Author: U.S. EPA (2016) (EPA/600/R-16/351). Washington, DC: U.S. Environmental Protection Agency. [EPA Report] HERO ID: 3452607