Columbia River Research Articles

River Discharge Mediates Extent of Phytoplankton and Harmful Algal Bloom Habitat in the Columbia River Estuary (USA) During North Pacific Marine Heat Waves

Marine heat waves (MHWs) have been associated with extensive harmful algal blooms (HABs) in the northeast Pacific Ocean, but the degree to which these large-scale oceanographic events are mirrored in nearshore environments has not been well established. We compared phytoplankton assemblages in the Lower Columbia River Estuary (LCRE) during two Pacific MHWs that took place in 2015 and 2019, with observations from 2017, a year with no MHW. These data were paired with environmental data from the summers of 2015–2019 to characterize differences in estuarine conditions during MHWs that promote phytoplankton assemblage transitions and identify HAB-conducive conditions. Bloom densities of HAB taxa, Pseudo-nitzschia spp. (4.16 × 106 cells L−1) and Gymnodinium catenatum (5.66 × 106 cells L−1), were noted in the estuary during 2015 and 2019, respectively, 2 years where Pacific MHWs occurred during the summer months. These blooms coincided with estuary temperatures that were 1–2 ℃ above and river discharge volumes 46–48% lower than decadal daily averages. We identified patterns in the densities of several algal taxa associated with MHW-mediated low discharge in the LCRE, such as declines in tychopelagic diatoms and increasing abundance of pelagic marine taxa. We conclude that low river discharge, through extension of saline habitat area and longer residence times, likely contributed to the development of the observed marine HABs in the estuary. MHWs and associated declines in discharge are projected to become more common in the Pacific Northwest with climate change, which may alter late summer phytoplankton assemblages in the LCRE.

Hydroinformatic tools and their potential in the search for missing persons in rivers

This research proposes a methodological approach to search floating bodies or floating body parts in rivers using hydroinformatic tools. These tools may allow possible search locations and potential release sites to be determined. The approach draws from hydrometric field information, two-dimensional (2D) hydrodynamic modeling, particle tracking (PT) models, and large-scale particle image velocimetry (LSPIV). This methodology was applied to a case study of the La Miel river in Colombia, where existing reports of deceased persons are available. A series of hydraulic accidents have been defined to represent the hydrodynamic and transport processes that occur in such situations. The results indicate that potential search locations, namely places where human floating bodies or floating body parts may be found, are principally on the left and right shores of recirculation systems.

Drivers for the artisanal fisheries production in the Magdalena River

We review knowledge on the Magdalena River in Colombia and its fish to identify those drivers that influence the artisanal fisheries production. We identify eight direct drivers (four natural and four anthropogenic) and at least four indirect drivers. Those drivers modify conditions in the fluvial network that promote fish movements, reproduction, and their larvae survivor. Landscape, rains, floods, connectivity of the fluvial net as land cover change, water pollution, hydropower, and alien species are the natural and anthropogenic direct drivers described in this article. The river–lake interaction dynamics in the Magdalena River are determined by two rainy cycles per year. Two seasonal flooding periods induce two cycles in the biological productivity of floodplains because water and sediment inputs. The most visible consequences in these hydrological cycles are the migrations of potamodromous fish and the periodic increase in the artisanal fishery production. Major floodplains are reducing their storage capacity by trapping ∼10%–40% of upstream sediment production. This process induces many research questions about rates of biomass production, carbon fluxes in the basin, impacts of human-induced erosion, and increasing rates of sediment load on floodplain connectivity, but still there is not enough data to answer them. Finally, we make some suggestions toward the sustainability of the Magdalena floodplains. The well-being of the floodplain ecosystems and their connectivity with the main river are the main tools to preserve and manage the ecosystem services of the Magdalena River and its floodplains lakes.

Socio-hydrological modeling of the tradeoff between flood control and hydropower provided by the Columbia River Treaty

Abstract. The Columbia River Treaty (CRT) signed between the United States and Canada in 1961 is known as one of the most successful transboundary water treaties. Under continued cooperation, both countries equitably share collective responsibilities of reservoir operations and flood control and hydropower benefits from treaty dams. As the balance of benefits is the key factor of cooperation, future cooperation could be challenged by external social and environmental factors which were not originally anticipated or change in the social preferences of the two actors. To understand the robustness of cooperation dynamics, we address two research questions. (i) How does social and environmental change influence cooperation dynamics? (ii) How do social preferences influence the probability of cooperation for both actors? We analyzed infrastructural, hydrological, economic, social, and environmental data to inform the development of a socio-hydrological system dynamics model. The model simulates the dynamics of flood control and hydropower benefit sharing as a function of the probability to cooperate, which in turn is affected by the share of benefits. The model is used to evaluate scenarios that represent environmental and institutional change and changes in political characteristics based on social preferences. Our findings show that stronger institutional capacity ensures equitable sharing of benefits over the long term. Under the current CRT, the utility of cooperation is always higher for Canada than non-cooperation, which is in contrast to the United States. The probability to cooperate for each country is lowest when they are self-interested but fluctuates in other social preference scenarios.

Broadscale distribution, abundance, and habitat associations of the invasive Asian clam (Corbicula fluminea) in the lower Columbia River, USA

AbstractThe Asian clam, Corbicula fluminea, is an invasive freshwater bivalve that has established populations across the globe and is known to have deleterious effects on natural and human systems. Yet, despite being present in the Columbia River (CR) for nearly a century, little is known about this invader's basic biology and ecology in this large river system. Thus, we undertook a field study to assess its (i) broadscale distribution and abundance, and (ii) associations with habitat characteristics in the lower CR. During 2019–2020, C. fluminea were collected from 27 shore‐based stations spanning 481 river kilometers of the lower CR, along with several habitat characteristics (bank slope, temperature, dissolved oxygen, pH, salinity, conductivity, chlorophyll‐a concentration, and sediment composition and % organic matter [OM]). C. fluminea abundance ranged from 0 to 430 ind. m−2. Most sites with abundances >100 ind. m−2 were located downstream of Bonneville Dam, whereas most sites with abundances <100 ind. m−2 were located upstream. Generalized linear models predicting the abundance of C. fluminea indicated significantly positive correlations with water temperature and % sand, and negative correlations with bank slope and sedimentary % OM. We also reviewed the global literature on abundance and habitat associations of C. fluminea and compared this with our own results. Our investigation represents the greatest spatial extent at which C. fluminea has been studied in the CR and our results provide a better understanding of the basic biology and ecology of this global invader, as well as provide natural resource managers with information on habitat conditions favorable for this invasive bivalve within temperate river ecosystems.

Measuring Estuarine Total Exchange Flow From Discrete Observations

The exchange between estuaries and the coastal ocean is a key dynamical driver impacting nutrient and phytoplankton concentrations and regulating estuarine residence time, hypoxia, and acidification. Estuarine exchange flows can be particularly challenging to monitor because many systems have strong vertical and lateral velocity shear and sharp gradients in water properties that vary over space and time, requiring high-resolution measurements in order to accurately constrain the flux. The total exchange flow (TEF) method provides detailed information about the salinity structure of the exchange, but requires observations (or model resolution) that resolve the time and spatial co-variability of salinity and currents. The goal of this analysis is to provide recommendations for measuring TEF with the most efficient spatial sampling resolution. Results from three realistic hydrodynamic models were investigated. These model domains included three estuary types: a bay (San Diego Bay), a salt-wedge (Columbia River), and a fjord (Salish Sea). Model fields were sampled using three different mooring strategies, varying the number of mooring locations (lateral resolution) and sample depths (vertical resolution) with each method. The exchange volume transport was more sensitive than salinity to the sampling resolution. Most (>90%) of the exchange flow magnitude was captured by three to four moorings evenly distributed across the estuarine channel with a minimum threshold of 1-5 sample depths, which varied depending on the vertical stratification. These results can improve our ability to observe and monitor the exchange and transport of water masses efficiently with limited resources.

Where and When Does Streamflow Regulation Significantly Affect Climate Change Outcomes in the Columbia River Basin?

AbstractThe Columbia River basin is a large transboundary basin located in the Pacific Northwest. The basin spans seven US states and one Canadian province, encompassing a diverse range of hydroclimates. Strong seasonality and complex topography are projected to give rise to spatially heterogeneous climate effects on unregulated streamflow. The basin's water resources are economically critical, and regulation across the domain is extensive. Many sensitivity studies have investigated climate impacts on the basin's naturalized hydrology; however, few have considered the large role of regulation. This study investigates where and when regulation affects projected changes in streamflow by comparing climate outcomes across 80‐member ensembles of unregulated and regulated streamflow projections at 75 sites across the basin. Unregulated streamflow projections are taken from an existing data set of climate projections derived from Coupled Model Intercomparison Project version 5 Global Climate Models. Regulated streamflow projections were modeled by the US Army Corps of Engineers and the US Bureau of Reclamation by using these unregulated flows as input to hydro‐regulation models that simulate operations based on current and historical water demands. Regulation dampens shifts in winter and summer streamflow volumes. Regulation generally attenuates changes in cool‐season high flow extremes but amplifies shifts in warm‐season and annual high flow extremes at historically snow‐dominant headwater reservoirs. Regulation reduces dry‐season low flow changes in headwater tributaries where regulation is large but elsewhere has little effect on changes in low flows. Results highlight the importance of accounting for water management in climate sensitivity analysis particularly in snow‐dominant basins.

Exotic Carbonate Mineralization Recovered from a Deep Basalt Carbon Storage Demonstration.

Mitigating climate change requires transformational advances for carbon dioxide removal, including geologic carbon sequestration in reactive subsurface environments. The Wallula Basalt Carbon Storage Pilot Project demonstrated that CO2 injected into >800 m deep Columbia River Basalt Group flow top reservoirs mineralizes on month-year timescales. Herein, we present new optical petrography, micro-computed X-ray tomography, and electron microscopy results obtained from sidewall cores collected two years after CO2 injection. As no other anthropogenic carbonates from geologic carbon storage field studies have been recovered, this world-unique sample suite provides unparalleled insight for subsurface carbon mineralization products and paragenesis. Chemically zoned nodules with Ca/Mn-rich cores and Fe-dominant outer rims are prominent examples of the neoformed carbonate assemblages with ankerite-siderite compositions and exotic divalent cation correlations. Paragenetic insights for the timing of aragonite, silica, and fibrous zeolites are clarified based on mineral texture and spatial relationships, along with time-resolved downhole fluid sampling. Collectively, these results clarify the mineralogy, chemistry, and paragenesis of carbon mineralization, providing insight into the ultimate fate and transport of CO2 in reactive mafic-ultramafic reservoirs.

Filling critical gaps in the space-time record of High Lava Plains and co-Columbia River Basalt Group rhyolite volcanism

Miocene rhyolitic volcanism of eastern Oregon, USA, can be divided into two main episodes. Mantle plume upwelling is thought to have generated Columbia River Basalt Group (CRBG) lavas and coeval >16.5−15 Ma silicic volcanism trending north−south from northeast Oregon to northern Nevada. Rhyolite volcanism of the 12−0 Ma High Lava Plains province has been ascribed to either buoyancy-driven westward plume spreading or to slab rollback and mantle convection spanning from southeast Oregon to Newberry Volcano to the west. The apparent ca. 15−12 Ma eruptive hiatus suggests that rhyolites of these provinces were a product of separate processes, yet this gap was based on incomplete data. The lack of data on ∼33 of the total ∼50 rhyolitic eruptive centers in the area where the two provinces overlap (117−119°W, 43−44°N) yields only tenuous relationships between these two provinces. We acquired 40Ar/39Ar ages for 29 previously unanalyzed rhyolite centers that confirm the existence of a rhyolitic eruptive episode concurrent with CRBG flood basalt volcanism. Rhyolite eruptions gradually initiated at ca. 17.5 Ma, and our new ages indicate that peak intensity of the first eruptive episode occurred between 16.3 Ma and 14.4 Ma. We refine the ca. 15−12 Ma rhyolitic eruptive hiatus to 14.4−12.1 Ma, where strong recommencement of rhyolite eruptions began with Beatys Butte at 12.05 Ma. We find two prominent fluxes in rhyolitic eruptive activity after 12.1 Ma as opposed to one continuous, age-progressive trend, at 12.1−9.6 Ma and 7.7−5.1 Ma, which are separated by an ∼2 m.y. period of decreased rhyolite volcanism. Rhyolite eruptions were scarce after 5.1 Ma, at which point most eruptions were associated with Newberry Volcano. Periodicity of rhyolite volcanism along the High Lava Plains demands more punctuated basalt inputs than what continuous partial melting from west-spreading plume material should generate. Our new data suggest that regional rhyolite eruptions are a series of episodic events related to the arrival and storage of mafic mantle magmas. Paucity in rhyolite eruptions from 14.4 Ma to 12.1 Ma is related to decreased flux of CRBG flood basalt magmas at ca. 15 Ma. Strong recommencement of rhyolite volcanism at 12.1 Ma is related to continued Northwest Basin and Range extension and a peak rotation rate of Siletzia affecting regional lithosphere weakened by CRBG volcanism. Waning rhyolitic eruptive activity from ca. 9.6 Ma to 7.7 Ma reflects a regional transition in the primary mode of accommodation of extension from Northwest Basin and Range normal faulting to extension and shearing of the Brothers Fault Zone. Rhyolite volcanism between 7.7 Ma and 5.1 Ma was driven by continued regional extension in an area less affected by CRBG magmatism. Post-5.1 Ma rhyolite eruptions occurred within crust not influenced by CRBG magmatism but impacted by both regional extension and the Cascadia subduction zone.

Maximizing salmonid bycatch survival with passively operated commercial fish traps

Commercial fish traps were recently implemented at a limited scale in the lower Columbia River in efforts to selectively harvest hatchery-origin fishes with minimal mortality of wild-origin salmonids listed under the U.S. Endangered Species Act. Prior studies of a modified passive trapping technique demonstrated nearly 100 % survival among adult salmonids released as bycatch. Building upon this research, additional survival studies for adult coho salmon, spring-run Chinook salmon, and summer-run Chinook salmon were conducted between 2019 and 2021 at two separate fish trap sites in the lower Columbia River. Over three years of study, we used mark-recapture and net pen holding methodologies to estimate post-release survival of Chinook salmon and coho salmon, respectively. Evaluating detections of Chinook salmon tagged and released from a passively operated fish trap in 2019, detection at Bonneville Dam over a mean 6.5 d upriver migration (167 km) was 1.000 (95 % CI: S ≥ 0.970) for the sample genetically assigned to populations originating upriver of Bonneville Dam. Through two separate net pen holding studies, post-release survival of coho salmon was estimated at 1.000 (95 % CI: S ≥ 0.975) over 4 d in 2020 and 0.965 (95 % CI: 0.948 ≤ S ≤ 0.969) over 6 d in 2021. Given that these analyses lacked control groups to adjust survival estimates for confounding mortality effects, study results are inherently conservative. Ultimately, the findings of our research support the conclusions of prior studies and further suggest that passively operated fish traps may allow for selective harvesting of targeted fish stocks with little to no mortality of adult salmonid bycatch.

Using spatial data for sampling prioritization and prediction of PFAS chemicals in fish tissue in the Columbia River Basin

Background and Aim U.S. tribes and states are challenged with identifying and characterizing the extent of per- and polyfluoroalkyl substances (PFAS) contamination and human exposure to PFAS, as well as developing effective and cost-efficient ways to prioritize site investigation. In the Columbia River Basin (CRB), particularly in and around the region’s tribal lands, the availability of PFAS occurrence data is limited and exposure is less characterized than in other parts of the country. This study aims to develop and pilot a predictive modeling workflow for prioritization of sampling locations that show potential for PFAS exposures in vulnerable populations in the CRB. Methods and Results While previous studies have mainly developed predictive models for PFAS in groundwater, this study develops and evaluates predictive models for PFAS in fish tissue. Understanding PFAS levels in fish is particularly important in CRB because it can be a major component of tribal and indigenous peoples’ diet. Existing spatial data in the region are leveraged including locations of known PFAS sources or contaminated sites and potential, yet unconfirmed, sources such as PFAS-related industry facilities, mining and refinery sites, airports, and landfills. Machine learning and statistical models employ these spatial data to predict PFAS concentrations in fish tissue in natural waters throughout the CRB and will be evaluated using empirical fish tissue occurrence data. Conclusions Model predictions help to identify areas in which high PFAS concentrations are likely to occur in fish tissue but sampling has not yet confirmed. This workflow for targeted prioritization of sampling investigations and the identification of contaminated natural resources will help U.S. tribes and states in the Columbia River Basin more efficiently manage waste, initiate clean-up activities, and identify opportunities for source reduction, thereby promoting healthy and resilient communities. Keywords PFAS, spatial analysis, predictive modeling, fish tissue, Columbia River Basin

Broad-scale eDNA sampling for describing aquatic species distributions in running waters: Pacific lamprey Entosphenus tridentatus in the upper Snake River, USA.

One of the most fundamental yet challenging tasks for aquatic ecologists is to precisely delineate the range of species, particularly those that are broadly distributed, require specialized sampling methods, and may be simultaneously declining and increasing in different portions of their range. An exemplar is the Pacific lamprey Entosphenus tridentatus, a jawless anadromous fish of conservation concern that is actively managed in many coastal basins in western North America. To efficiently determine its distribution across the accessible 56,168 km of the upper Snake River basin in the north-western United States, we first delimited potential habitat by using predictions from a species distribution model based on conventionally collected historical data and from the distribution of a potential surrogate, Chinook salmon Oncorhynchus tshawytscha, which yielded a potential habitat network of 10,615 km. Within this area, we conducted a two-stage environmental DNA survey involving 394 new samples and 187 archived samples collected by professional biologists and citizen scientists using a single, standardized method from 2015 to 2021. We estimated that Pacific lamprey occupied 1875 km of lotic habitat in this basin, of which 1444 km may have been influenced by recent translocation efforts. Pacific lamprey DNA was consistently present throughout most river main stems, although detections became weaker or less frequent in the largest and warmest downstream channels and near their headwater extent. Pacific lamprey were detected in nearly all stocked tributaries, but there was no evidence of indigenous populations in such habitats. There was evidence of post-stocking movement because detections were 1.8-36.0km upstream from release sites. By crafting a model-driven spatial sampling template and executing an eDNA-based sampling campaign led by professionals and volunteers, supplemented by previously collected samples, we established a benchmark for understanding the current range of Pacific lamprey across a large portion of its range in the interior Columbia River basin. This approach could be tailored to refine range estimates for other wide-ranging aquatic species of conservation concern.

Pathways and Estimate of Aquifer Recharge in a Flood Basalt Terrain; A Review from the South Fork Palouse River Basin (Columbia River Plateau, USA)

Aquifer recharge is one of the most important hydrologic parameters for understanding available groundwater volumes and making sustainable the use of natural water by minimizing groundwater mining. In this framework, we reviewed and evaluated the efficacy of multiple methods to determine recharge in a flood basalt terrain that is restrictive to infiltration and percolation. In the South Fork of the Columbia River Plateau, recent research involving hydrologic tracers and groundwater modeling has revealed a snowmelt-dominated system. Here, recharge is occurring along the intersection of mountain-front alluvial systems and the extensive Miocene flood basalt layers that form a fractured basalt and interbedded sediment aquifer system. The most recent groundwater flow model of the basin was based on a large physio-chemical dataset acquired in laterally and vertically distinctive locations that refined the understanding of the intersection of the margin alluvium and the spatially variable basalt flows that filled the basin. Modelled effective recharge of 25 and 105 mm/year appears appropriate for the basin’s plain and the mountain front, respectively. These values refine previous efforts on quantifying aquifer recharge based on Darcy’s law, one-dimensional infiltration, zero-flux plane, chloride, storage, and mass-balance methods. Overall, the combination of isotopic hydrochemical data acquired in three dimensions and flow modelling efforts were needed to simultaneously determine groundwater dynamics, recharge pathways, and appropriate model parameter values in a primarily basalt terrain. This holistic approach to understanding recharge has assisted in conceptualizing the aquifer for resource managers that have struggled to understand aquifer dynamics and sustainable withdrawals.

An ethic of co-inhabitation for the biocultural conservation of rivers

During the 20th century, numerous rivers were pumped, channeled, stratified, dammed, and diverted. Diverse water courses and bodies (rivers, streams, lakes, wetlands, estuaries, and aquifers) were transformed for agricultural irrigation and energy purposes, supplying urban areas or simply favoring economic interests. These transformations were driven by a mentality inherited from modernity that has led to understanding and exploiting rivers as mere water channels or fuel for hydroelectric power plants. This one-dimensional mentality continues to promote the conversion of rivers into paved channels and/or their clogging by constructing large hydroelectric dams worldwide. In this article, I use the conceptual framework of the “3Hs” (Habits, Habitats, co-in-Habitants) of my biocultural ethics to criticize the problematic modern habit of indiscriminately channeling water courses, which leads to the proliferation of homogeneous habitats (crossed by captive water courses) that entail the suffering or elimination of myriads of co-inhabitants. These co-inhabitants include both the exuberant biological diversity that inhabits rivers (freshwater fish, insects, plants, algae, and bacteria) and the rich cultural diversity of human communities that co-inhabit watersheds. In addition, the “3Hs” model of my biocultural ethics can guide us to protect and/or regenerate connections between human societies and rivers, transforming not only biophysical habitats but also our symbolic and material culture. I explore how the perspective of my biocultural ethics supports and is supported by: (i) the philosophical revaluation of the concept of meander developed by environmental thinker Irene Klaver; (ii) innovative scientific methodologies to study river biota proposed by freshwater ecologist Tamara Contador; (iii) the recent legal attribution of biocultural rights to rivers in Colombia, New Zealand, and India; and (iv) expressions of indigenous poets and other artists that communicate deep river-human interconnections. On the one hand, adopting my proposed biocultural ethics requires us to abandon a one-dimensional mentality to embrace ancient and new forms of systemic, contextual, complex, and dynamic thinking to understand and value rivers. On the other, we must cultivate habits of care for riparian habitats where we co-inhabit with various co-inhabitants (humans and other-than-humans), seeking their well-being. Thus, an ethic of co-inhabitation emerges that guides us to value and defend the biocultural conservation of rivers.

Predation probabilities and functional responses: How piscivorous waterbirds respond to pulses in fish abundance

How predators respond to changes in prey abundance (i.e., functional responses) is foundational to consumer–resource interactions, predator–prey dynamics, and the stability of predator–prey systems. Predation by piscivorous waterbirds on out-migrating juvenile steelhead trout (Oncorhynchus mykiss) is considered a factor affecting the recovery of multiple Endangered Species Act-listed steelhead populations in the Columbia River basin. Waterbird functional responses, however, may vary by predator species and location, with important implications to predator management strategies. We used a 13-year dataset on waterbird abundance across seven breeding colonies (three Caspian tern [Hydroprogne caspia], two double-crested cormorant [Nannopterum auritum], and two California and ring-billed gull [Larus californicus and Larus delawarensis] colonies) and steelhead tag-recovery data (>645,000 tagged and >32,000 recovered steelhead) to quantify weekly predation probabilities and functional responses across waterbird species, colonies, and years. Weekly predation probabilities were highly variable, ranging from 0.01 to 0.30 at tern colonies, 0.01 to 0.20 at cormorant colonies, and 0.03 to 0.13 at gull colonies. Per capita predation probabilities were an order of magnitude higher at inland tern and cormorant colonies relative to estuary colonies of the same species. Terns displayed Type II functional responses across colonies and years, where predation probabilities peaked at low steelhead abundances and declined as steelhead abundance increased (i.e., predator swamping). Cormorants nesting at the large estuary colony (several thousand birds) displayed a Type III functional response, but cormorants nesting at the smaller inland colony (several hundred birds) displayed a Type II response. Consumption probabilities of steelhead by gulls remained consistent across a large range of steelhead availability, suggesting a Type I or a Type III functional response, but a lack of colony abundance data prevented quantifying functional responses. The level of tern predation combined with Type II functional responses indicate possible population-level impacts that could destabilize small or declining prey populations. Conversely, the apparent Type III functional responses of gulls and estuary nesting cormorants are indicative of prey switching behaviors targeted at periods of high steelhead abundance. Our results illustrate the complexity of predator–prey interactions and the importance of quantifying predator- and location-specific functional responses when predicting the efficacy of management strategies to enhance prey populations.

International Law Application to Transboundary Pollution: Solutions to Mitigate Mining Contamination in the Elk–Kootenai River Watershed

The Elk Valley is home to five of the six largest mines in British Columbia, with ongoing plans for further expansion. These headwater coal mines have contributed to selenium pollution in the freshwater ecosystems of the transboundary Elk – Kootenai River watershed, evidenced in part by the $60 million fine imposed on Teck Resources Ltd. under Canada’s Fisheries Act in 2021 for the ‘deposit of deleterious substances’. Indigenous communities, including the Ktunaxa Nation, and various other organizations on both sides of the border, alongside governments in the United States, have been calling for higher standards of mining pollution control originating in Canada and for the International Joint Commission to make recommendations on this issue. Two agreements exist between the countries that may be relevant here, including the Boundary Waters Treaty (1909) and Columbia River Treaty (1964). In this article, these agreements describing the potential role of the International Joint Commission are analyzed, along with the outlining of the current process for this organization to make recommendations to resolve this ongoing, hot-button issue. The examples from case law and other international agreements pertaining to pollution are used to formulate a two-part conclusion in the form of (1) a short-term solution to effectively communicate and facilitate a resolution of transboundary mining pollution in the Elk – Kootenay River watershed; (2) a long-term solution to settle future disagreements regarding transboundary pollution between Canada and the United States

Spatiotemporal distribution of Ceratonova shasta in the lower Columbia River Basin and effects of exposure on survival of juvenile chum salmon Oncorhynchus keta.

In the Columbia River Basin (CRB), USA, anthropogenic factors ranging from dam construction to land use changes have modified riverine flow and temperature regimes and degraded salmon habitat. These factors are directly implicated in native salmon and steelhead (Oncorhynchus species) population declines and also indirectly cause mortality by altering outcomes of ecological interactions. For example, attenuated flows and warmer water temperatures drive increased parasite densities and in turn, overwhelm salmonid resistance thresholds, resulting in high disease and mortality. Outcomes of interactions between the freshwater myxozoan parasite, Ceratonova shasta, and its salmonid hosts (e.g., coho O. kisutch and Chinook salmon O. tshawytscha) are well-described, but less is known about effects on chum salmon O. keta, which have a comparatively brief freshwater residency. The goal of this study was to describe the distribution of C. shasta relative to chum salmon habitat in the CRB and assess its potential to cause mortality in juvenile chum salmon (listed as threatened in the CRB under the U.S. Endangered Species Act). We measured C. shasta densities in water samples collected from chum salmon habitat throughout the lower CRB during the period of juvenile chum salmon outmigration, 2018–2020. In 2019, we exposed caged chum salmon fry from two hatchery stocks at three C. shasta-positive sites to assess infection prevalence and survival. Results demonstrated: (1) C. shasta was detected in spawning streams from which chum salmon have been extirpated but was not detected in contemporary spawning habitat while juvenile chum salmon were present, (2) spatiotemporal overlap occurs between C. shasta and juvenile chum salmon in the Columbia River mainstem, and (3) low densities of C. shasta caused lethal infection in chum salmon fry from both hatchery stocks. Collectively, our results suggest C. shasta may limit recovery of chum salmon now and in the future.

Spring peak flows control abundance of Cladophora in a Hydropower‐Impacted River

AbstractThe lower Deschutes River represents the 161‐km reach downstream of three hydroelectric dams flowing to its confluence at the Columbia River. We examined hydrology and nutrient chemistry from 2015–2017 to 2019 to determine factors affecting periphyton community composition and abundance following a change in the outlet structure and depth of release waters from the major upstream impoundment. The periphyton community composition was abundant and diverse in 2015 and 2016 and lower in 2017 and 2019. Filamentous chlorophytes were dominant in the first 2 years but were sparse in the subsequent years. Cyanophytes were dominant in 2017 and 2019. The expectation entering the study was that altered nutrient chemistry associated with the change in operations resulted in conditions more favorable for periphyton growth. Concentrations of total and soluble phosphorous are independent of reservoir operations, being high in all years because of natural weathering of P‐rich volcanic rocks in the basin. Concentrations of TN and DIN were low all study years, resulting in a system that was N‐limited, but with similar chemistry among the study years. The hydrology during 2015 and 2016, with abundant chlorophytes, exhibited low flow in the spring, whereas high spring flows were observed in the latter years. We conclude that high spring flows were far more influential in affecting the periphyton community composition in the lower Deschutes River compared to nutrient chemistry.

Life in the Fast Lane: Feeding and Growth of Juvenile Steelhead and Chinook Salmon in Main‐Stem Habitats of the Columbia River Estuary

AbstractVery little is known about the ecology of juvenile Pacific salmon Oncorhynchus spp. that rapidly traverse estuaries. For these species and life history types, main‐stem habitats are thought to largely function as migratory corridors rather than as productive habitats that support feeding or growth, although little research has focused on this issue. This is especially true in the highly modified Columbia River estuary, where it is unclear whether fast‐migrating salmon benefit from extensive tidal marsh restoration. To address this deficit, we sampled migratory juvenile steelhead O. mykiss and Chinook Salmon O. tshawytscha at locations spread across nearly 200 km of the Columbia River estuary. Our results demonstrated that these juvenile salmon were actively feeding and growing as they moved downstream; dominant prey included chironomids, other insects, and corophiid and gammarid amphipods. We also observed variation in diet composition and quantity between years, which was likely associated with the highly contrasting river conditions. Insulin‐like growth factor 1 hormone levels and the size of juvenile salmon increased as the fish moved downstream, suggesting that prey quality and quantity were sufficient to fuel rapid growth, which may increase survival in marine waters. Our results have direct management implications for habitat restoration and suggest the potential for competition between hatchery and wild salmon. Overall, our results support a fundamental shift in the view of main‐channel estuarine habitats from serving primarily as a migration corridor to serving as productive habitat where rapidly moving salmon actively feed and grow.

Genetics Reveal Long-Distance Virus Transmission Links in Pacific Salmon.

Simple SummaryThe transmission of viruses between host populations is essential for viruses to persist on the landscape. Therefore, the identification of specific transmission links can provide insights into how a virus moves from source to recipient (sink) populations, allowing for the development of strategies to interrupt transmission routes and control viral disease. For the fish pathogen infectious hematopoietic necrosis virus (IHNV), this study identifies three transmission links associated with the emergence of IHNV in coastal Washington steelhead trout populations between 2007 and 2011. The links were identified by the genetic typing of virus isolates obtained from coastal fish and potential source fish from the Columbia River Basin. Three exact genotype matches were found, indicating at least three introductions of virus from Columbia fish to coastal fish during years of the emergence event. Likely sources were juvenile fish in the Columbia region experiencing disease, and the first detected recipient populations in all cases were adult fish returning to coastal hatcheries. Variation in timing and distance for these three transmission links will provide Pacific Northwest fish health managers with a better understanding of IHNV transmission routes from Columbia region fish to coastal steelhead trout.In the coastal region of Washington State, a major pathogen emergence event occurred between 2007 and 2011 in which steelhead trout (Oncorhynchus mykiss) experienced a high incidence of infection and disease outbreaks due to the rhabdovirus infectious hematopoietic necrosis virus (IHNV). Genetic typing showed that the introduced viruses were in the steelhead-specific MD subgroup of IHNV and indicated the most likely source was a virus from the nearby Columbia River Basin. In the current study, full-length viral glycoprotein (G) gene sequences were determined for 55 IHNV isolates from both coastal and Columbia fish populations to identify specific source populations and infer mechanisms of transmission to coastal steelhead. We identified three transmission links based on exact fullG genotype matches between Columbia and coastal fish. In all cases, the likely source population was infected juvenile fish, and sink populations were adult fish returning to coastal rivers to spawn. The time intervals between detection in source and sink populations varied from 6 months to nearly 4 years, suggesting different transmission pathways. Surprisingly, distances between source and sink populations varied between 140 and 1000 km. These results confirm repeated introductions of virus from Columbia River Basin fish as the cause of emergence of MD virus on the Washington coast from 2007 to 2011.