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Denitrification is a critical process regulating the removal of bioavailable nitrogen (N) from natural and human-altered systems. While it has been extensively studied in terrestrial, freshwater, and marine systems, there has been limited communication among denitrification scientists working in these individual systems. Here, we compare rates of denitrification and controlling factors across a range of ecosystem types. We suggest that terrestrial, freshwater, and marine systems in which denitrification occurs can be organized along a continuum ranging from (1) those in which nitrification and denitrification are tightly coupled in space and time to (2) those in which nitrate production and denitrification are relatively...
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Watersheds draining the Arctic Coastal Plain (ACP) of Alaska are dominated by permafrostand snowmelt runoff that create abundant surface storage in the form of lakes, wetlands, and beaded streams. These surface water elements compose complex drainage networks that affect aquatic ecosystem connectivity and hydrologic behavior. The 4676 km2 Fishand Creek drainage basin is composed of three watersheds that represent a gradient of theACP landscape with varying extents of eolian, lacustrine, and fluvial landforms. In each watershed, we analyzed 2.5-m-resolution aerial photography, a 5-m digital elevationmodel, and river gauging and climate records to better understand ACP watershed structureand processes. We show that...
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Interactions and feedbacks between abundant surface waters and permafrost fundamentally shapelowland Arctic landscapes. Sublake permafrost is maintained when the maximum ice thickness (MIT) exceedslake depth and mean annual bed temperatures (MABTs) remain below freezing. However, decliningMIT since the1970s is likely causing talik development below shallow lakes. Here we show high-temperature sensitivity towinter ice growth at the water-sediment interface of shallow lakes based on year-round lake sensor data.Empirical model experiments suggest that shallow (1m depth) lakes have warmed substantially over the last30years (2.4°C), withMABT above freezing5 of the last 7years.This is incomparison to slower ratesofwarming...
Synopsis: One recent study examining Eurasian watermilfoil (Myriophyllum spicatum L., hereafter milfoil) invasions using landscape-level variables found that the amount of forest land cover in the catchment is consistently negatively related to milfoil presence (Buchan and Padilla, 2000). These results suggest that further research is needed to examine the relationships between natural and anthropogenic landscape features and macrophyte cover. The ability of lake and landscape features to predict a variety of macrophyte cover metrics using 54 north temperate lakes were examined. Univariate regression analyses demonstrated that these macrophyte cover metrics are predicted by a wide range of predictor variables, most...
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Lakes are dominant and diverse landscapefeatures in the Arctic, but conventional land coverclassification schemes typically map them as a singleuniform class. Here, we present a detailed lake-centricgeospatial database for an Arctic watershed in northernAlaska. We developed a GIS dataset consisting of 4362lakes that provides information on lake morphometry,hydrologic connectivity, surface area dynamics,surrounding terrestrial ecotypes, and other importantconditions describing Arctic lakes. Analyzing thegeospatial database relative to fish and bird survey datashows relations to lake depth and hydrologic connectivity,which are being used to guide research and aid in themanagement of aquatic resources in the NationalPetroleum...
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The Arctic Coastal Plain (ACP) of northern Alaskaconsists of an extremely low gradient, lake-richlandscape that is characterized by a complex networkof aquatic habitats and surface features stronglyinfluenced by permafrost dynamics. Much is unknownabout the form, function, and ecological conditions inthis unique hydrologic setting. Amplified climatechange and landscape responses in the Arctic furthercomplicate the capacity to separate natural variabilityfrom land use effects that may occur with petroleumdevelopment. A comprehensive, multi-disciplinaryreview and analysis of recent studies and initialinventory and monitoring in the Fish Creek watershedon the ACP provided guidance to develop a frameworkfor future aquatic...
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When resources are spatially and temporally variable, consumers can increasetheir foraging success by moving to track ephemeral feeding opportunitiesas these shift across the landscape; the best examples derive from herbivore–plant systems, where grazers migrate to capitalize on the seasonal waves ofvegetation growth. We evaluated whether analogous processes occur in watershedssupporting spawning sockeye salmon (Oncorhynchus nerka), askingwhether seasonal activities ofpredators and scavengers shift spatial distributionsto capitalize on asynchronous spawning among populations of salmon. Bothglaucous-winged gulls and coastal brown bears showed distinct shifts in theirspatial distributions over the course of the summer,...
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How local geomorphic and hydrologic features mediate the sensitivity of stream thermal regimesto variation in climatic conditions remains a critical uncertainty in understanding aquatic ecosystem responsesto climate change.We used stable isotopes of hydrogen and oxygen to estimate contributions of snow and rainfallto 80 boreal streams and show that differences in snow contribution are controlled by watershed topography.Time series analysis of streamthermal regimes revealed that streams in rain-dominated, low-elevation watershedswere 5–8 times more sensitive to variation in summer air temperature compared to streams draining steepertopography whose flows were dominated by snowmelt. This effect wasmore pronounced...
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Beaded streams are widespread in permafrost regionsand are considered a common thermokarst landform.However, little is known about their distribution, how andunder what conditions they form, and how their intriguingmorphology translates to ecosystem functions and habitat.Here we report on a circum-Arctic survey of beaded streamsand a watershed-scale analysis in northern Alaska using remotesensing and field studies.We mapped over 400 channelnetworks with beaded morphology throughout the continuouspermafrost zone of northern Alaska, Canada, and Russiaand found the highest abundance associated with mediumto high ground-ice content permafrost in moderately slopingterrain. In one Arctic coastal plain watershed, beaded...
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This dataset is a component of a complete package of products from the Connect the Connecticut project. Connect the Connecticut is a collaborative effort to identify shared priorities for conserving the Connecticut River Watershed for future generations, considering the value of fish and wildlife species and the natural ecosystems they inhabit. Click here to download the full data package, including all documentation. These datasets represent aquatic core areas and aquatic buffers, in combination with terrestrial cores and connectors they spatially represent the ecological network derived from the CTR LCD project. Lotic cores: This set of lotic (river and stream) core areas, in combination with the lotic cores...
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Lakes are prevalent in the Arctic and thus play a key role in regional hydrology. Since manyArctic lakes are shallow and ice grows thick (historically 2 m or greater), seasonal ice commonly freezes tothe lake bed (bedfast ice) by winter’s end. Bedfast ice fundamentally alters lake energy balance and meltoutprocesses compared to deeper lakes that exceed the maximum ice thickness (floating ice) and maintainperennial liquid water below floating ice. Our analysis of lakes in northern Alaska indicated that ice-out ofbedfast ice lakes occurred on average 17 days earlier (22 June) than ice-out on adjacent floating ice lakes (9July). Earlier ice-free conditions in bedfast ice lakes caused higher open-water evaporation,...
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In Arctic ecosystems, freshwater fish migrateseasonally between productive shallow water habitatsthat freeze in winter and deep overwinter refuge in riversand lakes. How these movements relate to seasonal hydrologyis not well understood.We used passive integratedtransponder tags and stream wide antennae to track1035 Arctic grayling in Crea Creek, a seasonally flowingbeaded stream on the Arctic Coastal Plain, Alaska. Migrationof juvenile and adult fish into Crea Creek peakedin June immediately after ice break-up in the stream. Fishthat entered the stream during periods of high flow andcold stream temperature traveled farther upstream thanthose entering during periods of lower flow and warmertemperature. We used generalized...
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Numerous studies utilizing remote sensing imagery and other methods have documented that thermokarst lakes are undergoing varied hydrological transitions in response to recent climate changes, from surface area expansion to drainage and evaporative desiccation. Here, we provide a synthesis of hydrological conditions for 376 lakes of mainly thermokarst origin across high-latitude North America. We assemble surface water isotope compositions measured during the past decade at five lake-rich landscapes including Arctic Coastal Plain (Alaska), Yukon Flats (Alaska), Old Crow Flats (Yukon), northwestern Hudson Bay Lowlands (Manitoba), and Nunavik (Quebec). These landscapes represent the broad range of thermokarst environments...
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Field measurements, satellite observations, and models document a thinning trend in seasonal Arcticlake ice growth, causing a shift from bedfast to floating ice conditions. September sea iceconcentrations in the Arctic Ocean since 1991 correlate well (r=+0.69, p<0.001) to this lakeregime shift. To understand how and to what extent sea ice affects lakes, we conducted modelexperiments to simulate winters with years of high (1991/92) and low (2007/08) sea ice extent forwhich we also had field measurements and satellite imagery characterizing lake ice conditions. Alakeice growth model forced with Weather Research and Forecasting model output produced a 7%decrease in lake ice growth when 2007/08 sea ice was imposed on...
We suggest an empirical approach for determining critical loads for inorganic nitrogen (N) deposition in wetfall to the central Rocky Mountains (USA). We define "critical loads" as a deposition amount above which natural resources can be negatively affected. The arithmetic average from 1992 to 1996 of annual inorganic N deposition in wetfall at the eight National Acid-Deposition Program (NADP) sites located at elevations >2500 m in the central Rocky Mountains ranged from 2.5 to 3.5 kg�ha-1�yr-1. In contrast, inorganic N deposition was <2.5 kg�ha-1�yr-1 at all 23 NADP sites below 2500 m in elevation. At the Niwot Ridge NADP site in the Colorado Front Range, a simple linear regression of inorganic N in wetfall with...
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This dataset is a component of a complete package of products from the Connect the Connecticut project. Connect the Connecticut is a collaborative effort to identify shared priorities for conserving the Connecticut River Watershed for future generations, considering the value of fish and wildlife species and the natural ecosystems they inhabit. Click here to download the full data package, including all documentation.This dataset represents the aquatic vulnerability to development index, which reflects the likelihood of development occurring in places in the uplands that are likely to impact the aquatic cores. Specifically, aquatic vulnerability is the product of the aquatic buffers, which represent the areas estimated...
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An important unresolved question is how populations of coldwater-dependent fishes will respond to rapidly warming water temperatures. For example, the culturally and economically important group, Pacific salmon (Oncorhynchus spp.), experience site-specific thermal regimes during early development that could be disrupted by warming. To test for thermal local adaptation and heritable phenotypic plasticity in Pacific salmon embryos, we measured the developmental rate, survival, and body size at hatching in two populations of sockeye salmon (Oncorhynchus nerka) that overlap in timing of spawning but incubate in contrasting natural thermal regimes. Using a split half-sibling design, we exposed embryos of 10 families...
Categories: Data, Publication; Types: Citation, Map Service, OGC WFS Layer, OGC WMS Layer, OGC WMS Service; Tags: Academics & scientific researchers, CLIMATE CHANGE IMPACT ASSESSMENT MODELS, CLIMATE CHANGE IMPACT ASSESSMENT MODELS, DATA REFORMATTING, DATA REFORMATTING, All tags...
Climate change is likely to impact terrestrial and aquatic ecosystems via numerous physical and biological mechanisms. This study outlines a framework for projecting potential impacts of climate change on lakes using linked environmental models. Impacts of climate drivers on catchment hydrology and thermal balance in Onondaga Lake (New York State) are simulated using mechanistic models HSPF and UFILS4. Outputs from these models are fed into a lake ecosystem model, developed in AQUATOX. Watershed simulations project increases in the magnitude of peak flows and consequent increases in catchment nutrient export as the magnitude of extreme precipitation events increases. This occurs concurrently with a decrease in annual...
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Conclusions: The proportion of wetlands in the watershed at different scales affects dissolved organic carbon (DOC) concentrations in downstream lakes and rivers. Thresholds/Learnings: Synopsis: This study quantifies how the proportion of wetlands in the watershed at different scales affects dissolved organic carbon (DOC) concentrations in downstream lakes and rivers. Whether the watershed influence varies with season or hydrologic type of lake was also examined. The scaling and modelling approach used offered a useful way to examine heterogeneity of land cover types within the watershed and spatial arrangements, while allowing generality of conclusions with a large sample size. Zones of increasing distance from...
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Intraspecific variation in the seasonal reproductive timing of Pacific salmon (Oncorhynchus sp.) has importantimplications for the resilience of salmon and for organisms in freshwater and terrestrial communities that dependon salmon resources. Stream temperature has well known associations with salmon spawn timing buthow stream and watershed geomorphology relates to the variation in salmon spawn timing is less understood.We used multivariate statistics applied to five environmental variables to compare conditions across36 watersheds in the Wood River basin in southwest Alaska. We found that the environmental conditionsin the first two axes of a principal components analysis (PCA) explained 76% of the variation in...
    map background search result map search result map Landscape indictors of human impacts to riverine systems Aquatic Cores and Buffers, CT River Watershed Aquatic Vulnerability to Development, CT River Watershed Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes Depth, ice thickness, and ice-out timing cause divergent hydrologic responses among Arctic lakes Threshold sensitivity of shallow Arctic lakes and sublake permafrost to changing winter climate A lake-centric geospatial database to guide research and inform management decisions in an Arctic watershed in northern Alaska... Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska A synthesis of thermokarst lake water balance in high-latitude regions of North America from isotope tracers Watershed geomorphology and snowmelt control stream thermal sensitivity to air temperature. Association between geomorphic attributes of watersheds, water temperature, and salmon spawn timing in Alaskan streams Thermal adaptation and phenotypic plasticity in a warming world: Insights from common garden experiments on Alaskan sockeye salmon Riding the crimson tide: mobile terrestrial consumers track phenological variation in spawning of an anadromous fish Drainage Network Structure and Hydrologic Behavior of Three Lake-Rich Watersheds on the Arctic Coastal Plain, Alaska Developing a Long-term Aquatic Monitoring Network Developing a Long-Term Aquatic Monitoring Network in a Complex Watershed of the Alaskan Arctic Coast Seasonal cues of Arctic grayling movement in a small Arctic stream: the importance of surface water connectivity Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes Depth, ice thickness, and ice-out timing cause divergent hydrologic responses among Arctic lakes Threshold sensitivity of shallow Arctic lakes and sublake permafrost to changing winter climate A lake-centric geospatial database to guide research and inform management decisions in an Arctic watershed in northern Alaska... Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska A synthesis of thermokarst lake water balance in high-latitude regions of North America from isotope tracers Seasonal cues of Arctic grayling movement in a small Arctic stream: the importance of surface water connectivity Drainage Network Structure and Hydrologic Behavior of Three Lake-Rich Watersheds on the Arctic Coastal Plain, Alaska Developing a Long-term Aquatic Monitoring Network Developing a Long-Term Aquatic Monitoring Network in a Complex Watershed of the Alaskan Arctic Coast Thermal adaptation and phenotypic plasticity in a warming world: Insights from common garden experiments on Alaskan sockeye salmon Watershed geomorphology and snowmelt control stream thermal sensitivity to air temperature. Association between geomorphic attributes of watersheds, water temperature, and salmon spawn timing in Alaskan streams Riding the crimson tide: mobile terrestrial consumers track phenological variation in spawning of an anadromous fish Aquatic Cores and Buffers, CT River Watershed Aquatic Vulnerability to Development, CT River Watershed Landscape indictors of human impacts to riverine systems