Direct and Indirect Effects of Organic Matter Sources on Denitrificaton in Florida Rivers

Denitrification removes large amounts of reactive nitrogen (N) from ecosystems via reduction of nitrate to dinitrogen gas. In aquatic ecosystems, the influences of terrestrial and aquatic sources of organic matter (OM) on denitrification are potentially complex. Terrestrially-derived OM is often less labile than autochthonous OM; it may inhibit denitrification directly via biochemical mechanisms; and it may indirectly inhibit denitrification by reducing light availability to—and thus OM exudation by—aquatic primary producers. Using a natural dissolved OM gradient among rivers of northern Florida, I investigated these mechanisms using laboratory denitrification assays subjected to factorial amendments of NO3- and dextrose, humic acid dosing, and cross-incubations of sediments and water. Results indicated that C-limitation increased with DOC concentrations, consistent with the indirect inhibition hypothesis. Blackwater neither depressed nor stimulated denitrification rates, indicating that this DOC neither directly inhibits nor acts as a usable OM source for denitrifiers

NSF Supported Socio-Environmental Research: How Do Crosscutting Programs Affect Research Funding, Publication, and Citation Patterns?

Recognizing the continued human domination of landscapes across the globe, social-ecological systems (SES) research has proliferated, necessitating interdisciplinary collaborations. Although interdisciplinary research started gaining traction in academic settings close to 50 years ago, formal frameworks for SES research did not develop until the late 1990s. The first National Science Foundation (NSF) funding mechanism specifically for interdisciplinary SES research began in 2001 and the SES-specific Coupled Natural Human (CNH) Systems program began in 2007. We used data on funded NSF projects from 2000 to 2015 to examine how SES research was funded, where the research is published, and the scholarly impact of SES research. Despite specific programs for funding SES research within the NSF, this type of research also received funding from non-SES mission programs (e.g., Ecosystem Science constituted 19% of grants in our study, and Hydrology constituted 16% of grants). Although NSF funding for SES research originates from across programs, the majority of products are published in journals with a focus on ecological sciences. Grants funded through the Coupled Natural Human Systems programs were more likely to publish at least one paper that was highly interdisciplinary (Biological Sciences [BE-CNH] constituted 70% of grants in program, and Geosciences [GEO-CNH] constituted 48% of grants) than the traditional disciplinary programs (Ecology [ES], 35% and Hydrology, 27%). This result highlights the utility of these cross-cutting programs in producing and widely disseminating SES research. We found that the number of citations was higher in BE-CNH and ES than other programs, pointing to greater scholarly impact of SES research in these NSF programs. Through our research, we identified the need for institutions to recognize research products and deliverables beyond the “standard” peer-reviewed manuscripts, as SES and interdisciplinary research and unconventional research products (e.g., popular press articles, online StoryMaps, workshops, white papers) continue to grow and are important to the broader societal impact of these types of research programs. This project demonstrates that the outcomes and products of grants awarded through the NSF CNH programs are important to furthering SES research and the programs should be valued and expanded in the future

Resolving the Drivers of Algal Nutrient Limitation from Boreal to Arctic Lakes and Streams

Nutrient inputs to northern freshwaters are changing, potentially altering aquatic ecosystem functioning through effects on primary producers. Yet, while primary producer growth is sensitive to nutrient supply, it is also constrained by a suite of other factors, including light and temperature, which may play varying roles across stream and lake habitats. Here, we use bioassay results from 89 lakes and streams spanning northern boreal to Arctic Sweden to test for differences in nutrient limitation status of algal biomass along gradients in colored dissolved organic carbon (DOC), water temperature, and nutrient concentrations, and to ask whether there are distinct patterns and drivers between habitats. Single nitrogen (N) limitation or primary N-limitation with secondary phosphorus (P) limitation of algal biomass was the most common condition for streams and lakes. Average response to N-addition was a doubling in biomass; however, the degree of limitation was modulated by the distinct physical and chemical conditions in lakes versus streams and across boreal to Arctic regions. Overall, algal responses to N-addition were strongest at sites with low background concentrations of dissolved inorganic N. Low temperatures constrained biomass responses to added nutrients in lakes but had weaker effects on responses in streams. Further, DOC mediated the response of algal biomass to nutrient addition differently among lakes and streams. Stream responses were dampened at higher DOC, whereas lake responses to nutrient addition increased from low to moderate DOC but were depressed at high DOC. Our results suggest that future changes in nutrient availability, particularly N, will exert strong effects on the trophic state of northern freshwaters. However, we highlight important differences in the physical and chemical factors that shape algal responses to nutrient availability in different parts of aquatic networks, which will ultimately affect the integrated response of northern aquatic systems to ongoing environmental changes

Community-powered urban stream restoration: A vision for sustainable and resilient urban ecosystems

Urban streams can provide amenities to people living in cities, but those benefits are reduced when streams become degraded, potentially even causing harm (disease, toxic compounds, etc.). Governments and institutions invest resources to improve the values and services provided by urban streams; however, the conception, development, and implementation of such projects may not include meaningful involvement of community members and other stakeholders. Consequently, project objectives may be misaligned with community desires and needs, and projects may fail to achieve their goals. In February 2020, the 5(th) Symposium on Urbanization and Stream Ecology, an interdisciplinary meeting held every 3 to 5 y, met in Austin, Texas, USA, to explore new approaches to urban stream projects, including ways to maximize the full range of potential benefits by better integrating community members into project identification and decision making. The symposium included in-depth discussion about 4 nearby field case studies, participation of multidisciplinary urban stream experts from 5 continents, and input from the Austin community. Institutional barriers to community inclusion were identified and analyzed using real-world examples, both from the case studies and from the literature, which clarified disparities in power, equity, and values. Outcomes of the symposium have been aggregated into a vision that challenges the present institutional approach to urban stream management and a set of strategies to systematically address these barriers to improve restoration solutions. Integrating community members and other stakeholders throughout the urban restoration process, and a transparent decision-making process to resolve divergent objectives, can help identify appropriate goals for realizing both the ecological and social benefits of stream restoration

Community-powered urban stream restoration: A vision for sustainable and resilient urban ecosystems

Este artículo contiene 16 páginas, 2 tablas, 3 figuras.Urban streams can provide amenities to people living in cities, but those benefits are reduced when streams become degraded, potentially even causing harm (disease, toxic compounds, etc.). Governments and institutions invest resources to improve the values and services provided by urban streams; however, the conception, development, and implementation of such projects may not include meaningful involvement of community members and other stakeholders. Consequently, project objectives may be misaligned with community desires and needs, and projects may fail to achieve their goals. In February 2020, the 5th Symposium on Urbanization and Stream Ecology, an interdisciplinary meeting held every 3 to 5 y, met in Austin, Texas, USA, to explore new approaches to urban stream projects, including ways to maximize the full range of potential benefits by better integrating community members into project identification and decision making. The symposium included in-depth discussion about 4 nearby field case studies, participation of multidisciplinary urban stream experts from 5 continents, and input from the Austin community. Institutional barriers to community inclusion were identified and analyzed using real-world examples, both from the case studies and from the literature, which clarified disparities in power, equity, and values. Outcomes of the symposium have been aggregated into a vision that challenges the present institutional approach to urban stream management and a set of strategies to systematically address these barriers to improve restoration solutions. Integrating community members and other stakeholders throughout the urban restoration process, and a transparent decision-making process to resolve divergent objectives, can help identify appropriate goals for realizing both the ecological and social benefits of stream restoration.Publication costs were covered by an award from the Society of Freshwater Science’s Endowed Publication Fund (https:// freshwater-science.org/publications/endowed-publication-fund).Peer reviewe

Invisible Trash: Emerging Contaminants in Streams and Rivers

Professor Megan Fork, Biology - Invisible Trash: Emerging Contaminants in Streams and River

This is your stream on drugs: Concentrations and loads of pharmaceuticals over one year in Baltimore streams

Presented by: Megan Fork – Postdoc at Cary Institute of Ecosystem Studies, [email protected] Co-authors: Alexander J. Reisinger, Jerker Fick, Emma J. Rosi Abstract: Pharmaceuticals are among the many anthropogenic chemical stressors faced by urban streams. We present results from one year of weekly monitoring of pharmaceuticals in stream water from eight catchments spanning an urbanization gradient in Baltimore, MD. Despite none of the streams receiving direct effluent discharge from wastewater treatment, we frequently detected pharmaceuticals in these streams. The total number of pharmaceutical detections over the year was positively correlated with population density, and the highest concentration of any pharmaceutical (3717 ng/L of acetaminophen) was found in a highly urbanized site furthest downstream. Repeated sampling revealed that pharmaceutical concentrations are highly dynamic over time, not correlated with stream discharge, and frequently below the analytical level of quantification. To account for these challenges, we used a number of methods to estimate annual loads of pharmaceuticals from this urban stream. We estimated that the equivalent of > 28,000 tablets of acetaminophen and > 9000 daily doses of antidepressants were discharged to the Chesapeake Bay in 2018 from this stream alone. In addition to developing a framework for estimating loads of pharmaceuticals in streams, this work highlights the importance of leaking infrastructure in determining the water quality of surface streams in urban landscapes. Biography: Dr. Fork’s work focuses on the direct and indirect effects of human activities such as climate change, urbanization, and construction/alteration of water bodies on the ecology of streams, rivers, lakes, and reservoirs. She combines concepts and approaches from multiple disciplines to characterize how these anthropogenic drivers impact the complex interactions that drive the movement and transformations of nutrients, contaminants, carbon, and water in aquatic ecosystems.Ope

Changing Source-Transport Dynamics Drive Differential Browning Trends in a Boreal Stream Network

Dissolved organic carbon (DOC) concentrations are increasing in freshwaters worldwide, with important implications for aquatic ecology, biogeochemistry, and ecosystem services. While multiple environmental changes may be responsible for these trends, predicting the occurrence and magnitude of "browning" and relating such trends to changes in DOC sources versus hydrologic transport remain key challenges. We analyzed long-term trends in DOC concentration from the two dominant landscape sources (riparian soils and mire peats) and receiving streams in a boreal catchment to evaluate how browning patterns relate to land cover and hydrology. Increases in stream DOC were widespread but not universal. Browning was most pronounced in small, forested streams, where trends corresponded to twofold to threefold increases in DOC production in riparian soils and increases in annual DOC export from a forested headwater. By contrast, DOC did not change in mire peats or streams draining catchments with high lake or mire cover, nor did we observe trends in DOC export from a mire-dominated headwater. The distinct long-term trends in DOC sources also altered concentration-discharge relationships, with a forested headwater shifting from transport-limited toward chemostasis, and a mire outlet stream shifting from chemostasis to source-limitated. Modified DOC supply to headwaters, together with altered seasonal hydrology and differences in the dominant water source along the stream network gave rise to predictable browning trends and consistent concentration-discharge relationships. Overall, our results show that the sources of DOC to boreal aquatic ecosystems are responding to environmental change in fundamentally different ways, with important consequences for browning along boreal stream networks

Changing Source-Transport Dynamics Drive Differential Browning Trends in a Boreal Stream Network

Dissolved organic carbon (DOC) concentrations are increasing in freshwaters worldwide, with important implications for aquatic ecology, biogeochemistry, and ecosystem services. While multiple environmental changes may be responsible for these trends, predicting the occurrence and magnitude of "browning" and relating such trends to changes in DOC sources versus hydrologic transport remain key challenges. We analyzed long-term trends in DOC concentration from the two dominant landscape sources (riparian soils and mire peats) and receiving streams in a boreal catchment to evaluate how browning patterns relate to land cover and hydrology. Increases in stream DOC were widespread but not universal. Browning was most pronounced in small, forested streams, where trends corresponded to twofold to threefold increases in DOC production in riparian soils and increases in annual DOC export from a forested headwater. By contrast, DOC did not change in mire peats or streams draining catchments with high lake or mire cover, nor did we observe trends in DOC export from a mire-dominated headwater. The distinct long-term trends in DOC sources also altered concentration-discharge relationships, with a forested headwater shifting from transport-limited toward chemostasis, and a mire outlet stream shifting from chemostasis to source-limitated. Modified DOC supply to headwaters, together with altered seasonal hydrology and differences in the dominant water source along the stream network gave rise to predictable browning trends and consistent concentration-discharge relationships. Overall, our results show that the sources of DOC to boreal aquatic ecosystems are responding to environmental change in fundamentally different ways, with important consequences for browning along boreal stream networks

Propagation of inflowing urban stormwater pulses through reservoir embayments

Flashy hydrology and high solute loads in stormflow are well-studied effects of the built environment on urban streams. The physical and chemical interactions between inflowing stormwater of urban streams and their termination in large impoundments, however, is poorly understood. Determining the spatial distribution of urban stormwater in reservoirs is an important step in understanding the effects of the heat and contaminant loads in these systems, which provide multiple services for adjacent cities. Here, we show that signals of stormwater from a small urban stream can propagate more than 800 m from the stream mouth. Stormflow can also break down the thermal stratification that exists during non-storm periods. Because the relative volume of inflowing water relative to stored water in a reservoir embayment determines the distance stormwater propagates, management of both the urban landscape (which affects runoff volumes) and of reservoir water levels affects the spatial footprint of urban stormwater. The physical and chemical effects of stormwater may have significant implications for nutrient and pollutant transport through and biogeochemical reactions in reservoirs, as well as habitat for organisms and processing of organic matter and greenhouse gases in these dynamic ecosystems