Clark Fork Research Articles

Timing of lake-level changes for a deep last-glacial Lake Missoula: optical dating of the Garden Gulch area, Montana, USA

Glaciolacustrine sediments in the Clark Fork River valley at Garden Gulch, near Drummond, Montana, USA record highstand positions of the ice-dammed glacial Lake Missoula and repeated subaerial exposure. During these highstands the lake was at greater than 65% of its recognized maximum capacity. The initial lake transgression deposited a basal sand unit. Subsequent cycles of lake-level fluctuations are recorded by sequences of laminated and cross laminated silt, sand, and clay deformed by periglacial processes during intervening periods of lower lake levels.Optically stimulated luminescence (OSL) dating of quartz sand grains, using single-aliquot regenerative-dose procedures, was carried out on 17 samples. Comparison of infrared stimulated luminescence (IRSL) from K-rich feldspar to OSL from quartz for all the samples suggests that they were well bleached prior to deposition and burial. Ages for the basal sand and overlying glaciolacustrine exposure surfaces are indistinguishable within one standard deviation, and give a weighted mean age of 20.9 ± 1.3 ka (n = 11). Based on sedimentological and stratigraphic analysis we infer that the initial transgression, and at least six cycles of lake-level fluctuation, occurred over time scales of decades to ∼2 ka. Bioturbated sandy slopewash dated at 10.6 ± 0.9 ka and 11.9 ± 1.2 ka unconformably overlies the upper glaciolacustrine deposits. The uppermost sediments, above the glaciolacustrine section, are younger than the Glacier Peak tephra (13.7–13.4 cal ka B.P.), which was deposited across parts of the drained lake basin, but has not been found at Garden Gulch.Our study indicates that glacial Lake Missoula reached >65 percent of maximum capacity by about 20.9 ± 1.3 ka and either partially or completely drained twelve times from this position. Rapid lowering from the lake's highstand position due to ice-dam failure likely led to scour in the downstream portions of the glacial Lake Missoula basin and megafloods in the Channeled Scabland.

Accumulation of metals in native wheatgrasses and wild ryes when grown on metal-contaminated soil from three mine sites in Montana.

One of the biggest challenges to successfully phytoremediate contaminated mine land soils is the identification of native plants that possess a broad adaptation to ecological sites and either exclude or uptake heavy metals of interest. This study evaluated forage concentrations of aluminum (Al), arsenic (As), chromium (Cr), cadmium (Cd), copper (Cu), iron (Fe), magnesium (Mn), nickel (Ni), lead (Pb), strontium (Sr), and zinc (Zn) in native wheatgrasses (WG) and wildryes (WR) when grown in soil originating from mine tailings from Clark Fork, Cabbage Gulch, and Keating surface mines in western Montana. Despite having metal concentrations that exceeded the upper limits of normal plant tissue for As, Cd, Sr, and Zn, bioconcentration factors (BCF), an indicator of plants ability to extract metals from the soil, were ≥ 1 only for Cd and Mn and were soil specific. Charleston Peak slender WG appears to have some potential has a Cd accumulator when grown on soils with pH levels of 5.01 and 4.26 compared to a more basic soil found in the Clark Fork (pH = 7.64). Due to BCF values ≥ 1 for Mn uptake, all basin WR cultivars/germplasms studied, First Strike slender and Secar WG could be possible materials for Mn accumulators in a phyto extraction program. However, based on BCF values and soil types used, none of the WG and WR studied could be considered as hyperaccumlulator species for Al, As, Cr, Cd, Cu, Fe, Mn, Ni, Pb, Sr, and Zn.

Repeated sedimentation and exposure of glacial Lake Missoula sediments: A lake-level history at Garden Gulch, Montana, USA

Abstract Glaciolacustrine sediments record lake transgression, regression, and subaerial modification of the silty lake-bottom of glacial Lake Missoula in the Clark Fork River valley. The sequence preserved at Garden Gulch, MT documents lake-level fluctuations at >65% of its full-pool volume. Twelve sedimentary cycles fine upwards from (1) very fine-grained sandy silt to (2) silt with climbing ripples to (3) rhythmically laminated silt and some clay. The cycles are fine-grained turbidites capped locally by thin layers of angular gravel derived from local bedrock outcrops. The gravels appear to be the toes of mass wasting lobes carried onto the exposed lakebed surface during repeated lake-level lowerings. Periglacial wedges, small rotational faults, involutions, and clastic dikes deform the tops of eleven cycles. The wedges are 10–30 cm wide, penetrate 30–70 cm deep, are spaced The lowest five cycles are thicker and display more periglacial modification at their tops than the upper seven cycles. The Garden Gulch section may represent as few as seven and as many as twelve substantial fillings and partial to complete drainings of glacial Lake Missoula.

Dams impact westslope cutthroat trout metapopulation structure and hybridization dynamics

Dams fragment aquatic networks and impact the evolutionary dynamics of migratory fish populations. Historically, the Lake Pend Oreille–lower Clark Fork River system in Idaho and Montana supported a large metapopulation of adfluvial westslope cutthroat trout (westslope). These fish matured in the lake and made upstream spawning migrations to their natal tributaries in the river. Currently, dams allow downstream passage for juvenile fish to the lake, but no upstream passage for adults. We examined 19 microsatellite and anonymous nuclear loci to characterize spatial patterns of non-native rainbow trout (rainbow) genetic introgression in westslope populations upstream and downstream of these dams. We detected hybridization at 20 of 42 sites sampled throughout the system, with rainbow introgression ranging from 1.1 to 99.8%. Rainbow introgression was higher in tributaries downstream of both dams (12 of 18 sites downstream vs 6 of 22 sites upstream). Within tributaries, hybrids were more common in lower sections and only one sampled site contained a hybrid swarm. Fish collected below both dams during the spawning migration were admixtures of westslope, rainbows and hybrids with an average rainbow introgression of 48%. Phenotypic criteria reduced rainbow introgression to less than 1% for putative westslope identified for selective upstream transport at both dams. Lack of upstream fish passage at these dams has likely constrained spread of hybridization and increased isolation among non-hybridized westslope populations by reducing the abundance of the migratory life history form in areas upstream of these dams.

Principles of geomorphic disturbance and recovery in response to storms

AbstractThe most important geomorphic responses to storms are qualitative changes in system state. Minor storms produce no state change or very rapid recovery to pre‐storm state, and extinction events wipe out the system. In other cases disturbance results in a state change, which may be transitional (change to a previously existing state), state space expansion (change to a new state), and clock‐resetting events that return the system to its initial state. Recovery pathways are much more varied than the monotonic progressions represented in classic vegetation succession and linear channel evolution models. Those linear sequential pathways are only one of several archetypal recovery pathways, which also include binary, convergent, divergent, and more complex networks. Filter‐dominated systems are more likely to follow linear sequential or convergent patterns, whereas amplifier‐dominance is characteristic of divergent and more complex mesh or fully‐connected patterns. Amplifier domination is also more likely to lead to evolutionary or state space expansion responses. Amplification and filtering in geomorphic response and recovery can be assessed using the 'Four R's' framework of response, resistance, relaxation, and recursion. High resistance and resilience, rapid relaxation times, and stable recursive feedback networks reduce or offset effects of disturbances, thus filtering their impacts. Conversely, low resistance and resilience, slow relaxation, and dynamically unstable feedbacks can exaggerate disturbances, creating disproportionately large and long‐lived impacts, thereby amplifying disturbances.Unless new filter mechanisms evolve (either autogenically or anthropically), or the number of extinction or clock‐resetting events increases, intensified storminess will result in more geomorphic variability. These ideas are applied to a case study of a flood on the Clark Fork River, Montana, USA. Copyright © 2016 John Wiley & Sons, Ltd.

Nature's complex flume — Using a diagnostic state-and-transition framework to understand post-restoration channel adjustment of the Clark Fork River, Montana

There is an imperfect symmetry between the patterns of channel evolution observed during laboratory flume experiments and those which materialize in rivers exposed to ambient environmental conditions that produce hydrogeomorphic fluxes which are more complex, contingent, and unpredictable. One strategy to improve our understanding of short- to medium-term channel evolution is to study landscapes that have undergone significant disturbance and have had their biogeomorphic templates reset to a known condition — in effect, creating a flume in nature. This study adopts a diagnostic state-and-transition framework to narrate and document baseline hypotheses for the potential evolutionary trajectories Clark Fork River, near Milltown, Montana. Following dam removal and remediation, a 5-km stretch of the Clark Fork River and its adjoining floodplain were reconstructed. Since flow was introduced to the newly constructed channel in December 2010, complex evolutionary trajectories have been observed on the Clark Fork's mainstem, its secondary channels, and floodplain. Focusing particularly on the river's secondary channels, this paper develops a typology of channel states that have been observed and demonstrates that multiple adjustment trajectories have materialized, sometimes within the same channel. A diagnostic state-and-transition framework offers a parsimonious strategy to quantitatively or qualitatively anticipate the influence of water, sediment, and ecological fluxes on channel evolution at the basin, reach, or segment scale. It provides environmental agencies with a robust method to devise spatially explicit scenario-based management plans for rivers in a variety of geomorphic settings.

Summer Stream Temperatures Influence Sculpin Distributions and Spatial Partitioning in the Upper Clark Fork River Basin, Montana

The upper Clark Fork River basin of western Montana supports a poorly understood sculpin (Uranidea spp.) fauna that has perplexed ichthyologists and fish ecologists since the late 1800s. During our study, the basin contained three sculpin taxa whose taxonomy was under revision. All three taxa were formerly referred to the genus Cottus but are now treated as Uranidea. Our goal was to improve understanding of the distribution and ecology of two of the taxa. From 2006 to 2009, we sampled 144 reaches in 31 streams and rivers to determine distributions of each taxa across the study area and within streams. We collected habitat data in 2007 and stream temperature data from 2006–2009 to identify correlates of sculpin distributions. In streams where both taxa occurred, Rocky Mountain Sculpin Uranidea sp. cf. bairdii were downstream and Columbia Slimy Sculpin U. sp. cf. cognata were upstream with a syntopic zone in between. Summer stream temperatures strongly influenced sculpin distributions, with mean August 2007...

Consequences of Actively Managing a Small Bull Trout Population in a Fragmented Landscape

AbstractHabitat fragmentation, which affects many native salmonid species, is one of the major factors contributing to the declines in distribution and abundance of Bull Trout Salvelinus confluentus. Increasingly, managers are considering options to maintain and enhance the persistence of isolated local populations through active management strategies. Understanding the ecological consequences of such actions is a necessary step in conservation planning. We used an individual‐based model to evaluate the consequences of an ongoing management program aimed at mitigating the anthropogenic fragmentation of the lower Clark Fork River in Montana. Under this program juvenile Bull Trout are trapped and transported from small, headwater source populations to Lake Pend Oreille, Idaho, for rearing, and adults are subsequently recaptured in their upstream migration and returned to the natal population for spawning. We examined one of these populations and integrated empirical estimates of demographic parameters to simulate different management scenarios where moderate (n = 4) and high (n = 8) numbers of age‐2, age‐3, or age‐4 Bull Trout were removed for transport with variable return rates under both demographic stochasticity and environmental perturbations. Our results indicated the risks from removal with no returns increased substantially when removal totals and age of Bull Trout removed from the simulated population increased. Specifically, removing eight age‐3 or age‐4 individuals resulted in 26% and 62% reductions in average adult population size, respectively, across simulations. We found the risks of transport were not likely alleviated with low (3%) or moderate (6%) return rates, and there were considerable risks of declines for the source population even when return rates were extremely high (>12%). Our simulations indicated little risk of declines for the source population with removals of age‐2 Bull Trout, and any risks were alleviated with low return rates. However, we found higher return rates were particularly beneficial in the presence of large, density‐independent perturbations.

The role of trust in restoration success: public engagement and temporal and spatial scale in a complex social‐ecological system

The social dimensions of river restoration are not well understood especially in the context of large‐scale restoration projects embedded in a complex social‐ecological system. This study used in‐depth interviews with diverse stakeholders to examine perceptions of restoration success on the Clark Fork River Superfund project in Western Montana. Trust emerged as critical to restoration success and was influenced by public engagement, and by spatial and temporal scale. At this large scale, multiple relationships between agencies,NGOs, businesses, landowners, and other stakeholders meant that building trust was a complicated endeavor. The large spatial scale and long time frame made public engagement challenging, and landowners in particular were critical of the project, expressing mistrust in both agencies and the project as a whole. However, projects focused on smaller spatial scales, such as particular stream reaches, appeared to inspire more effective collaboration. Relationships between organizations were important at this large scale, but inter‐organizational conflict affected trust across the project. Further, because trust requires accepting vulnerability, recognizing the differential vulnerability that particular groups and communities experience, based on the risks and benefits they accrue relative to the project, is important.

Cottus schitsuumsh, a new species of sculpin (Scorpaeniformes: Cottidae)in the Columbia River basin, Idaho-Montana, USA.

Fishes of the genus Cottus have long been taxonomically challenging because of morphological similarities among species and their tendency to hybridize, and a number of undescribed species may remain in this genus. We used a combination of genetic and morphological methods to delineate and describe Cottus schitsuumsh, Cedar Sculpin, a new species, from the upper Columbia River basin, Idaho-Montana, USA. Although historically confused with the Shorthead Sculpin (C. confusus), the genetic distance between C. schitsuumsh and C. confusus (4.84-6.29%) suggests these species are distant relatives. Moreover, the two species can be differentiated on the basis of lateral-line pores on the caudal peduncle, head width, and interpelvic width. Cottus schitsuumsh is also distinct from all other Cottus in this region in having a single small, skin-covered, preopercular spine. Haplotypes of mtDNA cytochrome oxidase c subunit 1 of C. schitsuumsh differed from all other members of the genus at three positions, had interspecific genetic distances typical for congeneric fishes (1.61-2.74% to nearest neighbors), and were monophyletic in maximum-likelihood trees. Microsatellite analyses confirmed these taxonomic groupings for species potentially sympatric with C. schitsuumsh and that fish used in morphological comparisons were unlikely to be introgressed. Its irregular distribution, in the Spokane River basin in Idaho and portions of the Clark Fork River basin in Montana, may have resulted from human-assisted translocation.

Novel Fish Communities: Native and Non-Native Species Trends in Two Run-of-the-River Reservoirs, Clark Fork River, Montana

Long-term (1955–2011) trends in fish community structure were investigated in Noxon and Cabinet Gorge Reservoirs, Montana, based on the analysis of gillnet catches since the construction of the reservoirs. Results of gillnetting show significant declines in several forage species in absolute and relative abundance since the mid-1990s. Catches have declined for forage species as a group and for individual species such as non-native yellow perch Perca flavescens, native suckers Catostomus spp., and native peamouth Mylocheilus caurinus. In contrast, the aggregate catches of the non-native predators increased greatly as a percentage of the total catch since the 1990s, including increases in catches of walleye Sander vitreus, and northern pike Esox lucius. As a result of the non-native species increases, species diversity has, overall, trended upward whereas species dominance based on the three most abundant species has decreased, as previously abundant forage species have been reduced and greater evenness has resulted. Overall, the fish community in the reservoirs has shifted from a natural, seasonally coldwater riverine system (pre-impoundment) to a modified, coldwater-managed (i.e., salmonid stocked) system in the 1950s through the 1970s to a coolwater system dominated by forage species in the 1980s and early to mid-1990s, and, most recently, to a coolwater system more strongly structured by non-native piscivores. This novel (i.e., native-non-native) community poses some difficult issues for managers on which species to proactively manage for. Additional effort is needed to assess benefits and costs of proactively managing for non-natives as part of successful, comprehensive management plans.

Spawning Success of Bull Trout Transported above Main‐Stem Clark Fork River Dams in Idaho and Montana

AbstractThree main‐stem dams have fragmented the Clark Fork River in Montana and Idaho for nearly 100 years. Since 2001, Bull Trout Salvelinus confluentus collected below the farthest downstream dam, Cabinet Gorge Dam, have been manually transported upstream so that they can return to natal spawning tributaries and contribute gametes to numerically depressed populations upstream from the dams. Although redd counts and radio telemetry data suggest that these adults attempted to spawn after upstream transport, spawning success has not been documented or quantified. We used genetic parentage assignments to determine whether adult Bull Trout were successfully spawning after being transported upstream. Parentage data were also used to examine reproductive success and spawning behavior of fish transported upstream (transports) as well as Bull Trout that spawned in the same tributaries but were not transported upstream (nontransports). We genotyped 1,362 juvenile Bull Trout collected in two Clark Fork River tributaries, East Fork Bull River and Graves Creek, from 2008 to 2010 as well as 184 adult Bull Trout collected below Cabinet Gorge Dam and in Clark Fork River tributaries from 2004 to 2010. Parentage data indicated that Bull Trout collected below Cabinet Gorge Dam did spawn after upstream transport; nearly 27% of the juveniles sampled in this study had at least one upstream transport parent. Reproductive success varied widely among the adults we assigned as parents. We observed a variety of spawning patterns including adults that spawned only once, annual repeat spawners, and alternate‐year spawners. Our data provide evidence that the upstream transport program is meeting its goal of increasing the number of spawning adults in Bull Trout populations upstream from Clark Fork River dams and highlights the fact that nontransported fish also make an important contribution to the local tributary populations.Received January 29, 2013; accepted August 28, 2013

A hybrid SVM-PSO model for forecasting monthly streamflow

The long-term streamflow forecasts are very significant in planing and reservoir operations. The streamflow forecasts have to deal with a complex and highly nonlinear data patterns. This study employs support vector machines (SVMs) in predicting monthly streamflows. SVMs are proved to be a good tool for forecasting the nonlinear time series. But the performance of the SVM depends solely upon the appropriate choice of parameters. Hence, particle swarm optimization technique is employed in tuning SVM parameters. The proposed SVM-PSO model is used in forecasting the streamflow values of Swan River near Bigfork and St. Regis River near Clark Fork of Montana, United States. Further SVM model with various input structures is constructed, and the best structure is determined using various statistical performances. Later, the performance of the SVM model is compared with the autoregressive moving average model (ARMA) and artificial neural networks (ANN's). The results indicate that SVM could be a better alternative for predicting monthly streamflows as it provides a high degree of accuracy and reliability.

The role of nanominerals and mineral nanoparticles in the transport of toxic trace metals: Field-flow fractionation and analytical TEM analyses after nanoparticle isolation and density separation

Nanominerals and mineral nanoparticles from a mining-contaminated river system were examined to determine their potential to co-transport toxic trace metals. A recent large-scale dam removal project on the Clark Fork River in western Montana (USA) has released reservoir and upstream sediments contaminated with toxic trace metals (Pb, As, Cu and Zn), which had accumulated there as a consequence of more than a century and a half of mining activity proximal to the river’s headwaters near the cities of Butte and Anaconda. To isolate the high-density nanoparticle fractions from riverbed and bank sediments, a density separation with sodium polytungstate (2.8g/cm3) was employed prior to a standard nanoparticle extraction procedure. The stable, dispersed nanoparticulate fraction was then analyzed by analytical transmission electron microscopy (aTEM) and flow field-flow fractionation (FlFFF) coupled to both multi-angle laser light scattering (MALLS) and high-resolution, inductively coupled plasma mass spectrometry (HR-ICPMS). FlFFF analysis revealed a size distribution in the nano range and that the elution profiles of the trace metals matched most closely to that for Fe and Ti. aTEM confirmed these results as the majority of the Fe and Ti oxides analyzed were associated with one or more of the trace metals of interest. The main mineral phases hosting trace metals are goethite, ferrihydrite and brookite. This demonstrates that they are likely playing a significant role in dictating the transport and distribution of trace metals in this river system, which could affect the bioavailability and toxicity of these metals.

Combining historical and process perspectives to infer ranges of geomorphic variability and inform river restoration in a wandering gravel‐bed river

ABSTRACTRestoration approaches such as dam removal and channel reconstruction have moved beyond the realm of small streams and are being applied to larger rivers. This development has substantial economic and ecological implications but may test gaps in our understanding of larger river systems and of restoration science. We examine how information about historical ranges of geomorphic variability can inform stream restoration in the context of the Clark Fork River, Montana, focusing on a study reach where one of the largest restoration projects to date was implemented, upstream of the recently removed Milltown Dam. Analysis of historical sources and aerial photographs of the Clark Fork River's pre‐mining, mining, and more recent history suggest that a wandering channel pattern has persisted despite variations in sediment supply and transport capacity. Predictive metrics for channel pattern also suggest a wandering pattern, transitional between braided and meandering, in this geomorphic setting. These analyses suggest that the creation of a single‐thread meandering channel, which incorporates structures to limit erosion and channel movement, is inconsistent with the historical range of variability in this reach. The perils of restoring channels to a condition different than the historical range of variability for their geomorphic setting were illustrated on the Clark Fork by flood‐induced avulsions of the restored channel that occurred soon after project construction. Application of an experimental approach to restoration, founded on the method of multiple working hypotheses, provides a means for embracing uncertainty, can maximize the potential for site‐specific restoration success, and can foster advances in restoration science. Copyright © 2012 John Wiley & Sons, Ltd.

Response of Algal Biomass to Large‐Scale Nutrient Controls in the Clark Fork River, Montana, United States1

Suplee, Michael W., Vicki Watson, Walter K. Dodds, and Chris Shirley, 2012. Response of Algal Biomass to Large‐Scale Nutrient Controls in the Clark Fork River, Montana, United States. Journal of the American Water Resources Association (JAWRA) 48(5): 1008‐1021. DOI: 10.1111/j.1752‐1688.2012.00666.xAbstract: Nutrient pollution is an ongoing concern in rivers. Although nutrient targets have been proposed for rivers, little is known about long‐term success of programs to decrease river nutrients and algal biomass. Twelve years of summer data (1998‐2009) collected along 383 km of the Clark Fork River were analyzed to ascertain whether a basin‐wide nutrient reduction program lowered ambient total nitrogen (TN) and total phosphorus (TP) concentrations, and bottom‐attached algal biomass. Target nutrient and algal biomass levels were established for the program in 1998. Significant declines were observed in TP but not TN along the entire river. Downstream of the city of Missoula, TP declined below a literature‐derived TP saturation breakpoint and met program targets after 2005; TN was below targets since 2007. Algal biomass also declined significantly below Missoula. Trends there likely relate to the city’s wastewater facility upgrades, despite its 20% population increase. Upstream of Missoula, nutrient reductions were less substantial; still, TP and TN declined toward saturation breakpoints, but no significant reductions in algal biomass occurred, and program targets were not met. The largest P‐load reduction to the river was from a basin‐wide phosphate laundry detergent ban set 10 years before, in 1989. We document that nutrient reductions in rivers can be successful in controlling algal biomass, but require achievement of concentrations below saturation and likely close to natural background.

The sequence and timing of large late Pleistocene floods from glacial Lake Missoula

Glacial Lake Missoula formed when the Purcell Trench lobe of the Cordilleran ice sheet dammed Clark Fork River in Montana during the Fraser Glaciation (marine oxygen isotope stage 2). Over a period of several thousand years, the lake repeatedly filled and drained through its ice dam, and floodwaters coursed across the landscape in eastern Washington. In this paper, we describe the stratigraphy and sedimentology of a significant new section of fine-grained glacial Lake Missoula sediment and compare this section to a similar, previously described sequence of sediments at Ninemile Creek, 26 km to the northwest. The new exposure, which we informally term the rail line section, is located near Missoula, Montana, and exposes 29 units, each of which consists of many silt and clay couplets that we interpret to be varves. The deposits are similar to other fine-grained sediments attributed to glacial Lake Missoula. Similar varved sediments overlie gravelly flood deposits elsewhere in the glacial Lake Missoula basin. Each of the 29 units represents a period when the lake was deepening, and all units show evidence for substantial draining of glacial Lake Missoula that repeatedly exposed the lake floor. The evidence includes erosion and deformation of glaciolacustrine sediment that we interpret happened during draining of the lake, desiccation cracks that formed during exposure of the lake bottom, and fluvial sand deposited as the lake began to refill. The floods date to between approximately 21.4 and 13.4 cal ka ago based on regional chronological data. The total number of varves at the rail line and Ninemile sites are, respectively, 732 and 583. Depending on lake refilling times, each exposure probably records 1350–1500 years of time. We present three new optical ages from the rail line and Ninemile sites that further limit the age of the floods. These ages, in calendar years, are 15.1 ± 0.6 ka at the base of the Ninemile exposure, and 14.8 ± 0.7 and 12.6 ± 0.6 ka midway through the rail line exposure. The sediment at the two sections was deposited during later stages of glacial Lake Missoula, after the largest outburst events.

Mercury and Other Mining-Related Contaminants in Ospreys Along the Upper Clark Fork River, Montana, USA

We investigated links between mining-related contaminants in river sediment and their occurrence in nestling ospreys (Pandion haliaetus) in the Clark Fork River Basin, Montana, USA. Blood and feather samples from 111 osprey chicks were collected during 4years from nests along river sections with greatly different sediment concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn), and mercury (Hg). No significant differences between river sections were found among Zn (3,150±160μg L(-1)) and Cd (<5μg L(-1)) concentrations in blood. Cu, Pb, and As concentrations in blood were significantly increased in chicks from the most contaminated river sections (mean values of 298, 8.9, and 100μg L(-1), respectively). Cu, Zn, and Pb concentrations increased significantly during a year of above-average river runoff combined with high suspended sediment loads in rivers. Total Hg concentrations in blood and feathers were highly correlated and depended on the geographic locations of the nests. The lowest blood concentrations of Hg were observed in the most upstream river section (mean 151μg L(-1)) where total sediment concentrations were increased (0.80mgkg(-1)). River sections with intermediate blood concentrations (mean 206 and 303μg L(-1)) were associated with low to intermediate sediment concentrations (0.058 and 0.46mgkg(-1)). The highest concentrations of Hg in ospreys (mean 548μg L(-1)) were observed downstream from a contaminated tributary (1-4mgkg(-1) in sediment). In river sections with lower Hg concentrations in sediment, there was a negative correlation between blood Hg concentration and chick mass, presumably due to high deposition rates into growing feathers. This relationship was absent in sections of high Hg exposure. Osprey blood and feathers are suitable for monitoring Hg in aquatic ecosystems; however, responses of As, Cd, Cu, Pb, and Zn are more subtle.

Use of genetic markers to aid in re-establishing migratory connectivity in a fragmented metapopulation of bull trout (Salvelinus confluentus)

Dams and other barriers fragment important migratory corridors for bull trout ( Salvelinus confluentus ) across the species range. Three dams constructed without fish passage facilities prevented migratory bull trout in the Lake Pend Oreille and Clark Fork River system in Idaho and Montana, USA, from returning to their natal spawning tributaries for nearly 100 years. We genotyped bull trout from 39 spawning tributaries to assemble a baseline data set that we used to develop a real-time genotyping and analysis protocol to assist with upstream fish transport decisions. Self-assignment tests and analysis of blind samples indicated that unknown individuals could be assigned to their region of origin with a high degree of confidence. From 2004 to 2010, genetic assignments were conducted for 259 adult bull trout collected below mainstem dams. Based on genetic assignments, 203 fish were transported upstream above one or more dams. This protocol has helped re-establish connectivity in a fragmented system, providing increased numbers of spawning adults for numerically depressed populations above the dams. We discuss the utility of genetic data for assisting with upstream passage decisions.

Lake Missoula and Its Floods

The city of Spokane lies astride the Spokane River, some 40 miles from its origination near Coeur d’Alene, Idaho. The convention center and hotel, site of the 65th annual meeting of SRM, are located right along the river, creating a beautiful and even idyllic setting. These qualities make it even harder to imagine a long-ago day when a miles-wide wall of water, measuring as much as 500 feet high, bore down on this site. Hours before, a great ice dam on glacial Lake Missoula (present-day Clark Fork River) had failed. The dam was as much as 2,500 feet in height, impounded a lake up to 2,000 feet deep, extended east in the intermontane valleys for 200 miles, and covered some 3,000 square miles. It probably contained over 500 cubic miles of water, approximating half the volume of Lake Michigan. It is now generally agreed that catastrophic fl oods, in accordance with prevailing ice age conditions, repeatedly issued from Lake Missoula, probably on the order of several tens of times. Geologists estimate that the latest and last of the fl oods occurred about 13,000 years ago, creating the observable effects on the ground today, while largely obscuring the effects of earlier fl oods. Most students of the fl oods support that this particular event and its effects should be named “Bretz’s Flood” after the early geologist J Harlen Bretz, who fi rst recognized in 1919 the effects of catastrophic fl ooding on the Columbia drainage of southeastern Washington, as well as the Columbia River Gorge, the Portland-Vancouver Basin, and the Willamette Valley of Oregon. Over the 2 million years of the last ice age, four major glaciations advanced into what is now the northwestern United States. The last of these, the Wisconsin glaciation, left clear evidence of its effects, while likely obscuring most of the evidence of earlier fl ooding. It is near-certain, however, that each of the many fl oods inundated thousands of square miles in what is now central and southeastern Washington to depths of hundreds of feet. Later study also showed that the many fl oods likely shared the same provenance, that is, the same cause and effect. Piecing together the available evidence, it appears that the full glacial climate was cold and dry, with strong winds that redistributed soil materials to the southeastern quadrant of the Columbia Basin. These processes created what is today called the Palouse, an area of wind-deposited silts (loess) over the underlying basalt that had literally oozed out of the earth over previous untold centuries. The winds created dune-like deposits of variable orientation and depth that today make up fertile farmland in southeastern Washington and adjacent Idaho. Bretz’s Flood followed the path of the many earlier fl oods and recreated the effects over thousands of square miles in the Columbia Basin. These can briefl y be considered in four major categories: 1) the channeled scablands, 2) the river canyon, 3) the Grand Coulee, and 4) Lake Lewis.