Coldwater Streams Research Articles

Synthesis of heat-integrated water networks: Integration of heat pumps

A typical heat-integrated water network (HIWN) synthesis problem aims to minimise freshwater and utility consumption while establishing trade-offs between operating and investment costs by exploring different water and heat integration opportunities. Heat integration between hot and cold water streams is performed to save external heating and cooling utilities required to achieve the target temperatures of these streams. This paper proposes a mathematical programming approach to integrate water-to-water heat pumps into the HIWNs. A simple cascade heat pump system with isobutane as a natural working fluid enables a larger temperature lift between the heat pump source and the sink. The objective function of the proposed mixed-integer nonlinear programming (MINLP) model is to minimise the total annualised cost (TAC). The TAC includes operating costs for freshwater, heating/cooling utilities, electricity, and investment in heat exchangers and heat pumps. A sensitivity analysis is performed to evaluate the economic feasibility of the system by varying the heating/electricity cost ratio and depreciation period for the capital investment. The results show that additional utility savings can be obtained by integrating heat pumps into the HIWNs. For threshold problems, a heat pump is feasible for heating/electricity price ratios from 1.175, and heating utility is replaced by electricity for a 1:1 ratio. However, for pinched problems, the feasibility of the heat pump is shifted to lower heating/electricity price ratios, from 0.3 to 0.5, depending on the annualisation factor for the investment.

Influence of Riparian Conditions on Physical Instream Habitats in Trout Streams in Southeastern Minnesota, USA

Rivers across the globe experience and respond to changes within the riparian corridor. Disturbance of the riparian corridor can affect warmwater, intermediate, and coldwater streams, which can negatively influence instream physical structure and biological communities. This study focused on assessing the influence of the riparian habitat on instream structure within the Whitewater River, a coldwater stream system within an agricultural watershed in southeastern Minnesota, USA. To understand the influence of the riparian zone on the physical instream habitat, twenty variables (riparian, n = 9; instream, n = 11) were measured at 57 sites across three forks of the Whitewater using a transect method every 10 m across a 150 m reach. We used a modified Wentworth scale approach to assess coarse and fine substrates to describe habitat conditions. Canonical correlation detected significant associations between riparian and instream variables across the river forks, and indicated that wider riparian buffers, more bank grass and shrubs, longer overhanging vegetation, limited bare soil, and more rocks on banks were significantly associated with increased instream cover, high levels of coarse substrates with reduced embeddedness, increased pool habitats, and reduced fine sediments. In contrast, excessive fine sediments, lack of riffle habitat, reduced coarse substrates, and high width to depth ratios indicative of an impaired instream habitat were associated with narrow riparian buffers and high percentages of bare soil on banks. Riparian corridors have the capacity to enhance and protect physical instream habitats and overall ecosystem health when managed properly. Wide, grassy riparian corridors with stable banks, overhanging vegetation, and limited shade from trees should protect and/or enhance the instream physical habitat, providing the structural diversity favored by aquatic communities. We recommend revising the current Best Management Practices to include monitoring for impairments in the riparia, while promoting and developing good land stewardship with private landowners which can be effective in improving river ecosystems in agricultural settings.

Modeling instream temperature from solar insolation under varying timber harvesting intensities using RPAS laser scanning

Stream temperatures are influenced by the amount of solar insolation they receive. Increasing stream temperatures associated with climate warming pose detrimental health risks to freshwater ecosystems. In British Columbia (BC), Canada, timber harvesting along forested streams is managed using riparian buffer zones of varying widths and designations. Within buffer zones, depending on distance from the stream, selective thinning may be permitted or harvest may be forbidden. In this study, we used airborne laser scanning (ALS) point cloud data acquired via a remotely piloted aircraft system (RPAS) to derive forest canopy characteristics that were then used to estimate daily incoming summer and fall solar insolation for five stream reaches in coastal conifer-dominated temperate forests in Vancouver Island, BC, Canada. We then examined empirical relationships between estimated insolation and actual instream temperature measurements. Based on these empirical relationships, the potential effects of timber harvest on instream temperatures were simulated by comparing scenarios of different riparian forest harvest intensities. Our results indicated that modeled solar insolation explained 43–90 % of the variation in observed stream reach temperatures, and furthermore, when a single cold-water stream reach was excluded explained an overall 81 % of variation. Simulated harvesting scenarios generally projected increases in maximum stream reach temperatures 1–2 °C in summer and early fall months. However, in a full clearcut scenario (i.e. where all trees were removed), maximum stream reach temperatures increased as much as 5.8 °C. Our results emphasize the importance of retaining riparian vegetation for the maintenance of habitable temperatures for freshwater-reliant fish with thermal restrictions. In addition, we demonstrate the feasibility of RPAS-based monitoring of stream reach shading and canopy cover, enabling detailed assessment of environmental stressors faced by fish populations under climate warming.

Spatial asynchrony and cross-scale climate interactions in populations of a coldwater stream fish.

Climate change affects populations over broad geographic ranges due to spatially autocorrelated abiotic conditions known as the Moran effect. However, populations do not always respond to broad-scale environmental changes synchronously across a landscape. We combined multiple datasets for a retrospective analysis of time-series count data (5-28 annual samples per segment) at 144 stream segments dispersed over nearly 1,000 linear kilometers of range to characterize the population structure and scale of spatial synchrony across the southern native range of a coldwater stream fish (brook trout, Salvelinus fontinalis), which is sensitive to stream temperature and flow variations. Spatial synchrony differed by life stage and geographic region: it was stronger in the juvenile life stage than in the adult life stage and in the northern sub-region than in the southern sub-region. Spatial synchrony of trout populations extended to 100-200 km but was much weaker than that of climate variables such as temperature, precipitation, and stream flow. Early life stage abundance changed over time due to annual variation in summer temperature and winter and spring stream flow conditions. Climate effects on abundance differed between sub-regions and among local populations within sub-regions, indicating multiple cross-scale interactions where climate interacted with local habitat to generate only a modest pattern of population synchrony over space. Overall, our analysis showed higher degrees of response heterogeneity of local populations to climate variation and consequently population asynchrony than previously shown based on analysis of individual, geographically restricted datasets. This response heterogeneity indicates that certain local segments characterized by population asynchrony and resistance to climate variation could represent unique populations of this iconic native coldwater fish that warrant targeted conservation. Advancing the conservation of this species can include actions that identify such priority populations and incorporate them into landscape-level conservation planning. Our approach is applicable to other widespread aquatic species sensitive to climate change.

Grass versus trees: A proxy debate for deeper anxieties about competing stream worlds

Stream restoration has become an increasingly important focus in southwestern Wisconsin's Driftless Area, an unglaciated, hilly pocket of the Upper Mississippi River Basin rich in groundwater-driven coldwater streams, recreationally important trout species, and agricultural communities. Climate change is driving a major increase in precipitation and flooding across this rural and often under-resourced region, effects complicated by the ongoing legacies of white settlement and the changes it wrought to area streams, including the burial of floodplains in sediment displaced off area hillslopes. As managers work to consider how to “restore” Driftless streams, riparian vegetation—grass versus trees—has become a central and surprisingly controversial node. Current stream restoration practice typically includes the removal of riparian trees, though that practice has come under increasing criticism. Grounded in more than 5 years of qualitative and biophysical fieldwork in the region, we build from interviews gathered with 18 Driftless Area stream restoration managers from 2018 to 2020 to point to the ways that managers leverage arguments about erosion, flooding, habitat, and angler access, among other things, in service of grass and trees. Indexing the surface flows and underflows of this restoration debate, we introduce the rhetorical concept of the proxy debate to argue that debates about grass versus trees are tethered to competing perspectives on scale, temporality, and dynamism, surficial distractions from much deeper anxieties about what a stream is and should be. We turn to the ways that these distractions serve to further distance the stream restoration enterprise from acknowledging the ongoing human and hydrologic legacies of settler colonialism, and we close by suggesting that careful attention to rhetorical power—both to what arguments say and do, and to what they elide—offers a tentative first step toward restoring lands and relations by questioning what is taken for granted and what lies beneath.

Performance analysis of the Thermo Osmotic Energy Conversion (TOEC) process for harvesting low-grade heat

Low-grade heat energy from resources below 100 °C is readily available in massive quantities worldwide. However, existing technologies face challenges in converting this heat power into usable forms of energy, such as electricity. This is primarily due to temperature fluctuations in these heat sources and the limited temperature gradient with the surrounding environment. To address this issue, a recently developed technology called thermo-osmotic energy conversion (TOEC) offers a promising solution for harvesting electrical energy from low-grade heat sources. In the TOEC method, a hydrophobic membrane facilitates the transfer of water vapor molecules from a moderately hot aqueous solution to a cold water stream. The resulting hydraulic pressure in the compressed water on the cold side can be harnessed using a hydro-turbine. Despite the many interesting features of TOEC technology, a comprehensive analysis of its performance under various operating conditions and membrane properties is currently lacking in the literature. In this study, we conducted a theoretical evaluation of the TOEC process based on mass and heat transfer phenomena, and we validated our findings with experimental data. Our results indicate that employing membranes with smaller pore size, low thickness, and high porosity, along with higher feed temperature and flowrates, can significantly enhance energy efficiency and power density. Specifically, we demonstrate that the utilization of hydrophobic membranes with nanometer-sized pores, coupled with hydraulic pressures ranging from 6.2 bar to 11.8 bar, enables us to achieve power densities exceeding 5 W/m2, given a 20 °C heat sink and a heat source temperature above 65 °C. Furthermore, we have determined that an applied hydraulic pressure of 9.4 bar yields the maximum energy efficiency value of 0.016%.

Applying High-Resolution Satellite and UAS Imagery for Detecting Coldwater Inputs in Temperate Streams of the Iowa Driftless Region

Coldwater streams are crucial habitats for many biota including Salmonidae and Cottidae species that are unable to tolerate warmer water temperatures. Accurate classification of coldwater streams is essential for their conservation, restoration, and management, especially in light of increasing human disturbance and climate change. Coldwater streams receive cooler groundwater inputs and, as a result, typically remain ice-free during the winter. Based on this empirical thermal evidence, we examined the potential of very high-resolution (VHR) satellite and uncrewed aerial system (UAS) imagery to (i) detect coldwater streams using semi-automatic classification versus visual interpretation approaches, (ii) examine the physical factors that contribute to inaccuracies in detecting coldwater habitats, and (iii) use the results to identify inaccuracies in existing thermal stream classification datasets and recommend coverage updates. Due to complex site conditions, semi-automated classification was time consuming and produced low mapping accuracy, while visual interpretation produced better results. VHR imagery detected only the highest quality coldwater streams while lower quality streams that still met the thermal and biological criteria to be classified as coldwater remained undetected. Complex stream and site variables (narrow stream width, canopy cover, terrain shadow, stream covered by ice and drifting snow), image quality (spatial resolution, solar elevation angle), and environmental conditions (ambient temperature prior to image acquisition) make coldwater detection challenging; however, UAS imagery is uniquely suited for mapping very narrow streams and can bridge the gap between field data and satellite imagery. Field-collected water temperatures and stream habitat and fish community inventories may be necessary to overcome these challenges and allow validation of remote sensing results. We detected >30 km of coldwater streams that are currently misclassified as warmwater. Overall, visual interpretation of VHR imagery it is a relatively quick and inexpensive approach to detect the location and extent of coldwater stream resources and could be used to develop field monitoring programs to confirm location and extent of coldwater aquatic resources.

Abundance, cover use, and clustering of brown trout spawning redds during stream habitat rehabilitation

AbstractAbundance, placement beneath cover and clustering of brown trout spawning redds were monitored throughout five spawning seasons (2016–2020) in a 4.8‐km reach of a Minnesota coldwater stream to assess the potential impacts of concurrent stream habitat rehabilitation projects. We anticipated that redd abundance (redds/100 m stream segments) and placement beneath cover (e.g. logs and branches, boulders, overhanging bank vegetation, aquatic macrophytes) would increase and redd clustering (placement within 1.5 m of other redds) would decline as stream sections were rehabilitated. Repeated redd counts were conducted for the entire stream reach during each of the five spawning seasons, and redd cover and clustering were documented. Before‐after comparison of impact (BACI) tests were used to compare redd abundances in control versus rehabilitated stream sections, and before‐after distributional tests compared redd placement beneath cover and redd clustering within rehabilitated sections. In total, 1895 brown trout spawning redds were documented within the study reach during the five spawning seasons combined. Redd abundance increased nearly fivefold throughout the 5‐year study period (from 3.5 to 15.5 redds/100 m), but no significant difference was detected in redd abundances between rehabilitated versus control stream sections. Redd placement beneath cover (63% beneath cover in total) also increased throughout the study, but at a rate nine to 45 times greater in stream sections rehabilitated during the study than in control or previously rehabilitated sections. Redd clustering remained unchanged (5‐year means = 35 to 46% of all redds clustered) in rehabilitated sections, but increased significantly through time (0% to 35%) in the control section. Stream habitat rehabilitation did not increase spawning redd abundance or reduce redd clustering in rehabilitated stream sections, but redd placement beneath cover increased after rehabilitation to levels present in other stream sections.

Water Management for Conservation and Ecosystem Function: Modeling the Prioritization of Source Water in a Working Landscape

Conservation in working landscapes is an important aspect of stream restoration. Landowners with agricultural water rights are increasingly adding instream flow as a beneficial use of their allocated water. However, stream restoration projects commonly focus on the quantity of water dedicated to the environment and overlook water quality. For cold-water ecosystems, the preservation of natural thermal regimes is a key to conservation efforts in the face of a changing climate. This study explored the effects of increasing stream flow using alternative water sources (e.g., instream runoff versus offchannel springs) to enhance cold-water stream habitat on a working cattle ranch. Using empirical data to create a steady-state stream flow and water temperature model, we evaluated temperature benefits and management trade-offs for ecological and agricultural water use. The modeled results showed that the source of water and the method used to deliver water to the channel affected the quality and extent of cold-water habitat. Offchannel spring water cooled 7-day average maximum temperatures and 7-day average mean temperatures by as much as 3.7°C and 2.9°C, respectively, but only when potential offchannel aquatic habitat was sacrificed for mainstem habitat. When offchannel, spring-fed habitat was provided, the value of spring water to the main channel decreased. Our findings suggest that source water thermal quality is of paramount importance for enhancing ecosystem function and improving cold-water habitat in working landscapes. In addition, the restoration of a historic spring channel may provide added ecosystem benefits by enhancing aquatic habitat for cold-water species.

Modeling stormwater management pond thermal impacts during storm events

Discharges of warm water from shallow stormwater management ponds during summer months into receiving headwater streams pose a risk to aquatic ecosystems in urban watersheds, especially in cool- and cold-water streams. Physically based models such as MINUHET have been used to assess the effects of thermal loading on receiving streams. However, these models require a significant amount of data and are complex to calibrate and use for the optimized designs that ensure protection of vulnerable aquatic life in urban stream ecosystems. This research introduces a user friendly and more accurate machine learning method to predict thermal profiles in stormwater ponds and the pond outlet discharge temperature to the receiving streams during storm events. Monitoring data were collected between 2014 and 2016 from three stormwater ponds in southern Ontario to train and test the new model. The new model is used to demonstrate the degree to which cooling effects can be achieved from remedial actions such as increasing the pond depth by dredging one meter and if a bottom-draw outlet is used instead of a mid-depth draw outlet. The methods presented in this study can be used to support an improved stormwater management pond design guidelines based on the key design objective that the thermal regime of the stormwater pond outlet discharge water must match the thermal regime of the receiving stream. The main objective is to avoid any discernable warming of the stream due to the stormwater pond discharge under a range of summer temperatures and storm event sizes.

Combined Energetic and Exergetic Performance Analysis of Air Bubbles Injection into a Plate Heat Exchanger: An Experimental Study

This paper aims to give a comprehensive energetic-exergetic performance analysis on the impacts of injecting-submillimeter of air bubbles into both sides of cold and hot water streams before the entrance port of a corrugated plate heat exchanger (C-PHE) having ten plates within counterflow configuration. Hence, optimize the energy and exergy effectiveness at different operating conditions for counter and parallel fluid flow configurations. Hot streams were studied in seven flow rates ranging from 280 L/h to 880 L/h with a regular step of 100 L/h, and constant hot water temperature and cold-water stream of 50 °C and 290 L/h, respectively. Hence, the air was discharged with four flow rates ranging between 150 and 840 L/h. The obtained results showed the vital role of the ABI technique in enhancing the NTU and effectiveness by 59% and 18.6%, respectively, for CWS. The entropy generation was reduced to 0.038 W/K and the augmentation entropy generation number to 0.087 at the low airflow rate for CWS, which are the main parameters for evaluating the EGM. These two parameters increase the Witte-Shamsundar-efficiency to a maximum value of 98.6% at the same operating conditions. Moreover, the exergy effectiveness was enhanced to a maximum value of 80.9% at a high ABI flow rate and low volumetric rate of the hot stream at CWS. The thermo-economic assessment has been carried out, which revelers the positive effects of ABI on the combined energetic and exergetic performance on both sides, i.e., hot and cold sides.

Heat transfer enhancement of water-cooled triply periodic minimal surface heat exchangers

Whether triply periodic minimal surface (TPMS) heat exchangers are applicable to cooling or cold storage systems as a cooler for supercritical carbon dioxide (SCO2) is undocumented. Here the conjugated heat transfer of SCO2 in TPMS Schoen-G heat exchanger and printed circuit heat exchanger (PCHE) was predicted based on three-dimensional steady turbulent Reynolds-averaged Navier-Stokes equations, energy equation and shear stress transport model using computational fluid dynamics software ANSYS CFX when SCO2 inlet temperature and pressure vary in 65–30 ℃ and (8–9)MPa. SCO2 in two heat exchangers is cooled under counter-flow conditions by a stream of cold water with given inlet temperature and mass flow rate. It was shown that the mean heat transfer coefficient of SCO2 in TPMS Schoen-G heat exchanger is larger than PCHE. As the inlet pressure rises, the friction factor increases and Nusselt number decreases in the heat exchangers due to decreased Reynolds number and Prandtl number, respectively. The friction factor ratio, Nusselt number ratio and performance evaluation criterion vary in the range of 0.38–0.50, 1.07–1.49, and 1.45–2.04 with Reynolds number and inlet temperature when the PCHE serves as a reference heat exchanger. The streamlines in TPMS Schoen-G heat exchanger are quite smooth even though the areas with a higher velocity appear. The streamlines in PCHE exhibit a spiral flow pattern to result in extra hydraulic loss. The heat transfer enhancement of TPMS Schoen-G heat exchanger is much better TPMS Schwarz-D heat exchanger at a Reynolds number higher than 16,000. The enhancement is attributed to a larger heat transfer surface area and more topological tortuosity without flow separation than PCHE.

Investigations on tube in tube metal foam heat exchanger

The heat transfer equipments with higher heat transfer ability are needed in several industrial applications. With conventional methods, size of the device increases and it becomes bulky. With the use of metal foam, it is possible to attain large ratios of surface to volume. Therefore, using metal foam in heat exchanging devices is crucial. The main reason behind the use of metal foam over conventional method is its weight-saving and impact-absorbing structures. Insertion of metal foam in heat exchangers for various applications can lead to greater effectiveness and heat transfer enhancement. It has been observed that very few researchers have participated in the area of double tube heat exchangers (DTHE) having annular spaces filled with metal foam. The present work deals with numerical and CFD analysis of double tube heat exchanger (DTHE) with metal foam having different pore densities differing from 10 PPI to 50 PPI & performance evaluation of the same by taking hot water stream and cold water stream as working fluids. The modelling was created in Creo & simulation was done with k-omega (2 equation) viscous model in Ansys fluent flow. In the present work, double tube heat exchanger was considered in counter flow mode with inner sided tube (Stainless Steel) ID 9.5 mm & OD 12.7 mm and outer sided tube (Galvanized Iron) ID 28 mm & OD 33.8 mm. For fully developed turbulent flow, total length was considered as 1.5 m. The water streams through inner tube and annular space were flowing at uniform and constant flow rates of 2 lpm and 10 lpm respectively. Hot water and cold water inlet temperatures were taken at 800c & 300c respectively. For the analysis nickel metal foam with 10 PPI to 50 PPI with 0.9 porosity was inserted in the annular spaces of DTHE. For different pore densities comparative analysis was done. It was found that with rise in pore density of metal foam heat transfer rate (HTC) and pressure drop increased for both numerical & mathematical results. CFD simulation results were in good agreement with results obtained from empirical correlations taken from literature.

Environmental Impacts of Large-Scale Spirulina (Arthrospira platensis) Production in Hellisheidi Geothermal Park Iceland: Life Cycle Assessment

Spirulina algae (Spirulina platensis) cultivated in geothermally powered photobioreactors is here proposed as a potentially resource efficient, zero-carbon, and nutritious alternative to conventional beef meat. Employing a standard life cycle assessment, environmental impacts of large-scale Spirulina production in this facility are calculated. The production facility is sited in Orka náttúrunnar (ON Power) Geothermal Park, Iceland, and benefits from resource streams accessible through Hellisheiði (Hellisheidi) power station, including renewable electricity for illumination and power usage, hot and cold water streams for thermal management, freshwater for cultivation, and CO2 for biofixation. During cultivation, GHG-intensive ammonia-based fertilizers are replaced with macronutrients sourced from natural open mines. LCA results show that production of 1 kg of wet edible biomass in this facility requires 0.0378 m2 non-arable land, 8.36 m3 fresh water and is carbon neutral with − 0.008 CO2-eq GHG emissions (net zero). Compared with conventionally produced meat from beef cattle, Spirulina algae cultured in the ON Power Geothermal Park, referred to in this study as GeoSpirulina, requires less than 1% land and water and emits less than 1% GHGs. Considering food and nutritional security concerns, cultivation in a controlled environment agriculture system assures consistent nutritional profile year-round. Moreover, GeoSpirulina biomass assessed in this study contains all essential amino acids as well as essential vitamins and minerals. While keeping a balanced nutrition, for every kg beef meat replaced with one kg GeoSpirulina, the average consumer can save ~ 100 kg CO2-eq GHGs. It is concluded that environmental impacts of GeoSpirulina production in the Hellisheidi facility are considerably lower than those of conventionally produced ruminants.Graphical abstract

Receiving heat from a PCM tank by using natural convection of water and NEPCM: A simulation for LHTES application

Latent heat thermal energy storage (LHTES) systems are widely used due to their ability to store a lot of heat energy as latent, and few studies have directly or indirectly investigated on the heat exchange methods with LHTES systems. In the present study, the free convection of a mixture of water and Nano-encapsulated phase change material (NEPCM) with a porous medium was used to exchange heat energy between a cold-water stream and a hot tank filled phase change material (PCM). NEPCM are nanostructures consisted of a solid shell and a PCM core, and the addition of these nanostructures to water has remarkable effects on the heat transfer parameters. In this research, a number of cases were simulated using computational fluid dynamic (CFD) to observe the impacts of injecting NEPCM to water, the porosity of the porous media and the location of the phase change zone on the average heat flux of the PCM tank. The results showed that increment of porosity number from 0.85 to 0.95 decreased the average heat flux of the PCM tank by 13.8%. Moreover, adding 3% NEPCM to water enhanced the average heat flux of the PCM tank by 22.2% and 18.4% when porosity numbers were 0.85 and 0.95, respectively.

Evaluation of two fish-based indices of biotic integrity for assessing coldwater stream health and habitat condition in Iowa’s driftless area, USA

Evaluation of two fish-based indices of biotic integrity for assessing coldwater stream health and habitat condition in Iowa’s driftless area, USA

The Central Valley Salmonid Story: Six Million Years in the Making

For over six million years, salmon and steelhead (known as salmonids) have returned to the California Central Valley. After swimming under the Golden Gate Bridge and through the San Francisco Bay, adult salmonids swim hundreds of miles up the Sacramento or San Joaquin Rivers. Before dams were built, three out of the five salmonid species swam from the Central Valley into high-elevation, cold-water streams within the Sierra Nevada, southern Cascades, and Coastal Mountain ranges to finish their life cycles. Unfortunately, barriers such as dams cut-off salmonids from their home streams. When salmonid populations decrease, the effects are felt across the ecosystem—everything from microbes to humans feels the disconnection between the rivers and the ocean. Governmental agencies and their partners are teaming up to restore Central Valley salmonid populations by reconnecting them to their habitats and putting them back into high-elevation streams.

Rating the Potential Suitability of Habitat in Michigan Stream Reaches for Arctic Grayling

Abstract Present-day environments and anticipated future conditions often pose a significant challenge to efforts to reintroduce extirpated species, highlighting the need for collaborative, thorough approaches to reintroductions. Such is the case in Michigan, where numerous partners are working to reintroduce Arctic Grayling Thymallus arcticus with hopes of reestablishing self-sustaining populations. With > 47,000 km of coldwater stream habitat in the state and limited numbers of eggs for reintroductions, a prioritization framework was needed to provide a standardized, fine-scale method for rating suitability of streams for reintroductions. Through facilitated discussions with stakeholders and experts, we developed an overall prioritization framework for rating Michigan streams with components evaluating a reach's thermal, instream habitat, biological, and connectivity characteristics. Within the context of this broader framework, we developed the habitat rating component for assessing suitability of instream conditions for egg, fry, juvenile, and adult life stages of Arctic Grayling. Life-stage-specific habitat metrics and scoring criteria from this effort were used to rate habitat conditions for 45 reaches in tributaries of Michigan's Manistee River, enabling identification of reaches likely having instream habitat most suitable for Arctic Grayling. Numbers of reaches meeting or exceeding 60%, 70%, and 80% of the maximum score for overall habitat suitability were 31, 8, and 1. Upon completion of the fish assemblage and connectivity components, the prioritization framework and habitat rating process described here will be used for comparing suitability among streams throughout the historical range of Arctic Grayling in Michigan and guiding reintroduction efforts. Though it will take considerable time before instream habitat suitability criteria can be evaluated for all life-stages of Arctic Grayling in Michigan, the collaborative stream prioritization framework developed for Arctic Grayling reintroduction can be readily adapted to reintroduction efforts for other species elsewhere.

Genetic Structure of Maryland Brook Trout Populations: Management Implications for a Threatened Species

AbstractBrook Trout Salvelinus fontinalis have declined across their native range due to multiple anthropogenic factors, including landscape alteration and climate change. Although coldwater streams in Maryland (eastern United States) historically supported significant Brook Trout populations, only fragmented remnant populations remain, with the exception of the upper Savage River watershed in western Maryland. Using microsatellite data from 38 collections, we defined genetic relationships of Brook Trout populations in Maryland drainages. Microsatellite analyses of Brook Trout indicated the presence of five major discrete units defined as the Youghiogheny (Ohio), Susquehanna, Patapsco/Gunpowder, Catoctin, and Upper Potomac, with a distinct genetic subunit present in the Savage River (upper Potomac). We did not observe evidence for widespread hatchery introgression with native Brook Trout. However, genetic effects due to fragmentation were evident in several Maryland Brook Trout populations, resulting in erosion of diversity that may have negative implications for their future persistence. Our current study supplements an increasing body of evidence that Brook Trout populations in Maryland are highly susceptible to multiple anthropogenic stresses, and many populations may be extirpated in the near future. Future management efforts focused on habitat protection and potential stream restoration, coupled with a comprehensive assessment framework that includes genetic considerations, may provide the best outlook for Brook Trout populations in Maryland.

Relating environmental variables with aquatic community structure in an agricultural/urban coldwater stream

BackgroundUrban areas are often built along large rivers and surrounded by agricultural land. This may lead to small tributary streams that have agricultural headwaters and urbanized lower reaches. Our study objectives assessed are as follows: (1) landscape, geomorphic, and water quality variables that best explained variation in aquatic communities and their integrity in a stream system following this agricultural-to-urban land use gradient; (2) ways this land use gradient caused aquatic communities to differ from what would be expected for an idealized natural stream or other longitudinal gradients; and (3) whether the impacts of this land use gradient on aquatic communities would grow larger in a downstream direction through the agricultural and urban developments. Our study area was an impaired coldwater stream in Michigan, USA.ResultsMany factors structured the biological communities along the agricultural-to-urban land use gradient. Instream woody debris had the strongest relationship with EPT (Ephemeroptera, Plecoptera, and Trichoptera) abundance and richness and were most common in the lower, urbanized watershed. Fine streambed substrate had the strongest relationship with Diptera taxa and surface air breather macroinvertebrates and was dominant in agricultural headwaters. Fish community assemblage was influenced largely by stream flow and temperature regimes, while poor fish community integrity in lower urban reaches could be impacted by geomorphology and episodic urban pollution events. Scraping macroinvertebrates were most abundant in deforested, first-order agricultural headwaters, while EPT macroinvertebrate richness was the highest downstream of agricultural areas within the urban zone that had extensive forest buffers.ConclusionEnvironmental variables and aquatic communities would often not conform with what we would expect from an idealized natural stream. EPT richness improved downstream of agricultural areas. This shows promise for the recovery of aquatic systems using well-planned management in watersheds with this agricultural-to-urban land use pattern. Small patches of forest can be the key to conserving aquatic biodiversity in urbanized landscapes. These findings are valuable to an international audience of researchers and water resource managers who study stream systems following this common agricultural-to-urban land use gradient, the ecological communities of which may not conform with what is generally known about land use impacts to streams.