Estimating Total and Bioavailable Nutrient Loading to Utah Lake from the Atmosphere

Anthropogenic activities have led to increases in the emission, atmospheric transport, and deposition of key nutrients. In addition, climate change along with anthropogenic soil disturbance has led to recent increases in the mobilization and transport of soils and other particles through the atmosphere, collectively described here as dust. These increased emissions have led to growing interest and concern over the composition of atmospheric deposition and total loading of nutrients to aquatic systems. In the last several decades, much effort has been directed towards the measurement and modeling of nitrogen deposition through wet and aerosol deposition. Less is known about the capacity for regional dusts to transport nutrients in meaningful quantities in space and time. This paper summarizes the state of knowledge on dust deposition, composition, and potential effects on aquatic ecosystems. More specifically, this paper focuses on the potential for atmospheric aerosol, dust, and wet deposition to contribute phosphorus and nitrogen to Utah Lake in Provo, Utah. As part of this effort this paper, a) summarizes recent estimates of dust deposition from Utah and elsewhere in the Great Basin, b) summarizes current knowledge on total and soluble phosphorus loading from dusts, and c) summarizes atmospheric deposition rates of nitrogen from wet, gaseous, and particulate sources. The above information is used to generate estimates of total (urban + regional) nutrient loading to Utah Lake based on local bootstrapped measurements and three attenuation scenarios. Based on the compiled information of observed deposition rates, 80% of estimates fell between 2 and 9 metric tons of Total Phosphorus (TP) deposition to Utah Lake per year. The annual deposition rate of the bioavailable fraction, here defined as the soluble plus organic fraction of phosphorus, is estimated at a minimum of 0.5 to a maximum of 7.9 metric tons, with probable deposition rates between 2-2.5 metric tons per year. Because there is an interest in determining the maximum possible deposition flux of P to Utah Lake, we determined the maximum loads based on the maximum measured deposition rates and phosphorus concentrations applied over the full year, and, extended the urban zone of influence to 2 and 3 times that observed at other large lakes as part of these estimates. Total nitrogen loading is estimated between 153 and 288 metric tons per year base on measurements and models produced elsewhere. Recommendations on best practices for the measurement of particulate deposition onto a large lake are also provided

Consequences of Didymo Blooms in the Transnational Kootenay River Basin

Stream habitat changes that affect primary consumers often indirectly impact secondary consumers such as fishes. Blooms of the benthic algae Didymosphenia geminata (Didymo) represent one such habitat change known to affect stream macroinvertebrates. However, the potential indirect trophic impacts on fish consumers via modifications to their diet are poorly understood. The overall goal of this project was to determine if Didymo blooms in streams of the Kootenay River basin of British Columbia and Montana affect the condition and growth of fishes, and to see whether trophic mechanisms were responsible for any observed changes. We therefore quantified the diet, condition, and growth rate of trout, charr, and sculpin in a paired, Didymo vs. reference study, during the summer of 2018 and across a gradient of Didymo abundance in 2019. In the 2018 study, trout diets were 81% similar despite obvious differences in the composition of macroinvertebrate assemblages between the Didymo and reference streams. Trout abundance was higher in the stream with Didymo, but the amount of invertebrates in the drift was higher in the stream without Didymo. Growth rate and energy demand by individual trout was similar between the two streams. In the 2019 study, across a gradient of coverage, Didymo abundance was correlated only with the percent of aquatic invertebrates in trout diets and did not affect diets of charr or sculpin. Variation in fish condition was low across study streams. Thus, Didymo blooms may impact trout diets to a small extent, but we found no evidence this impact translates to changes in condition or growth. The relationship of fish abundance to Didymo blooms bears further study, but we found no obvious trophic mechanisms that would explain any differences. We suggest future studies prioritize research on potential impacts during winter months and on species with limited mobility that may be most greatly impacted by Didymo

Sediment source fingerprinting as an aid to large-scale landscape conservation and restoration: A review for the Mississippi River Basin

Reliable quantitative information on sediment sources to rivers is critical to mitigate contamination and target conservation and restoration actions. However, for large-scale river basins, determination of the relative importance of sediment sources is complicated by spatiotemporal variability in erosional processes and sediment sources, heterogeneity in sediment transport and deposition, and a paucity of sediment monitoring data. Sediment source fingerprinting is an increasingly adopted field-based technique that identifies the nature and relative source contribution of sediment transported in waterways. Notably, sediment source fingerprinting provides information that is independent of other field, modeling, or remotely sensed techniques. However, the diversity in sampling, analytical, and interpretive methods for sediment fingerprinting has been recognized as a problem in terms of developing standardized procedures for its application at the scale of large river basins. Accordingly, this review focuses on sediment source fingerprinting studies conducted within the Mississippi River Basin (MRB), summarizes unique information provided by sediment source fingerprinting that is distinct from traditional monitoring techniques, evaluates consistency and reliability of methodological approaches among MRB studies, and provides prospects for the use of sediment source fingerprinting as an aid to large-scale landscape conservation and restoration under current management frameworks. Most MRB studies reported credible fingerprinting results and found near-channel sources to be the dominant sediment sources in most cases, and yet a lack of standardization in procedural steps makes results difficult to compare. Findings from MRB studies demonstrated that sediment source fingerprinting is a highly valuable and reliable sediment source assessment approach to assist land and water resource management under current management frameworks, but efforts are needed to make this technique applicable in large-scale landscape conservation and restoration efforts. We summarize research needs and discuss sediment fingerprinting use for basin-scale management efforts with the aim of encouraging that this technique is robust and reliable as it moves forward

Plastic Rain in Protected Areas of the United States

Eleven billion metric tons of plastic are projected to accumulate in the environment by 2025. Because plastics are persistent, they fragment into pieces that are susceptible to wind entrainment. Using high-resolution spatial and temporal data, we tested whether plastics deposited in wet versus dry conditions have distinct atmospheric life histories. Further, we report on the rates and sources of deposition to remote U.S. conservation areas. We show that urban centers and resuspension from soils or water are principal sources for wet-deposited plastics. By contrast, plastics deposited under dry conditions were smaller in size, and the rates of deposition were related to indices that suggest longer-range or global transport. Deposition rates averaged 132 plastics per square meter per day, which amounts to \u3e1000 metric tons of plastic deposition to western U.S. protected lands annually

Sediment Dynamics in the Bear River-Mud Lake-Bear Lake System

The overarching goal of this project was to compile and analyze a variety of existing datasets, and generate several new datasets, to advance our understanding of how the Bear River Mud Lake-Bear Lake system functions, how it has, or is expected to change, identify which components are degraded or vulnerable to degradation, and determine if/where critical data and/or knowledge gaps exist. We conducted a series of analyses to evaluate changes in hydrology and suspended sediment, collected sediment cores from nine locations in Mud Lake to evaluate how sedimentation rates, sediment sources and water quality have changed over time, and utilized historical air photos and satellite imagery to document changes in Bear Lake’s shoreline. Hydrologic analyses indicate that low, median and high flows have not changed systematically at the Inlet Canal in terms of their long-term averages, since the 1940s. However, all three flow metrics have increased in terms of variability and have experienced longer duration wet and dry periods over the past three decades. We note a paucity of long-term hydrologic datasets for the Bear River-Dingle Marsh-Bear Lake system and additional monitoring would greatly help ensure that we are able to monitor trends throughout the system more carefully. We compiled suspended sediment data from all available sources and concluded, similar to previous studies, that Mud Lake appears to serve as a sediment sink for sediment, but the sediment trapping efficiency appears to vary considerably within and among years. Similar to the flow data, we note an unfortunate paucity of suspended sediment data and strongly recommend more rigorous and continuous monitoring of sediment in all parts of the Bear River-Mud Lake-Bear Lake system. Existing data and monitoring programs are insufficient to identify trends over time. The nine sediment cores extracted from Mud Lake provide a longer-term perspective on sediment dynamics. Results demonstrate that Mud Lake has historically and continues to serve as a net sediment sink. Two of the six dated cores document continuous deposition over the past 120 years, while the other four cores show truncated profiles in the 1950s. Visual inspection of the cores, as well as analysis of organic, calcium carbonate and mineral fractions occurring in the cores demonstrate highly variable history of sediment sources and water quality conditions in Mud Lake. Analysis of diatom algae species provides more detailed information regarding water quality conditions, indicating that Mud Lake has changed from a planktonic glacial lake, to a cold water, low nutrient environment and has existed as a mesotrophic environment with moderate water quality over the past century. Given the detailed information that diatoms can provide regarding historical water quality, we suggest that a similar diatom study examining the past 150 years in Bear Lake’s history could be worthwhile. Elemental analysis of Mud Lake sediments indicate two significant shifts in sediment sources, one coincident with diversion of Bear River into Mud Lake approximately 100 years ago, and a recent shift, within the past 10 years as silver, mercury and rare earth elements have increased considerably. Analysis of Bear Lake’s shoreline from historical imagery shows considerable amount of deposition has occurred in most areas around the lake in the past several decades. The shoreline at low water levels has moved lakeward by 30 to 50 meters (100 to 160 feet) in several locations and as much as 500 m (1600 feet) in the northwest corner of the lake, near St. Charles Creek. Notably, the only location where we document shoreline erosion (i.e., the shoreline moving landward for a given water elevation) is along the eastern edge of the lake, near Porcupine Hollow, Peterson Hollow and Bear Lake State Park. Further, we document that approximately 10% of the beach area in the northwest corner of the lake near St. Charles Creek has transitioned to vegetation cover between 2003 and 2016

Timing and Cause of Water Level Fluctuations in Kluane Lake, Yukon Territory, Over the Past 5000 Years

We reconstructed late Holocene fluctuations of Kluane Lake in Yukon Territory from variations in bulk physical properties and carbon and nitrogen elemental and isotopic abundances in nine sediment cores. Fluctuations of Kluane Lake in the past were controlled by changes in climate and glaciers, which affected inflow of Slims and Duke rivers, the two largest sources of water flowing into the lake. Kluane Lake fluctuated within a narrow range, at levels about 25 m below the present datum, from about 5000 to 1300 cal yr BP. Low lake levels during this interval are probably due to southerly drainage of Kluane Lake to the Pacific Ocean, opposite the present northerly drainage to Bering Sea. Slims River, which today is the largest contributor of water to Kluane Lake, only rarely flowed into the lake during the period 5000 to 1300 cal yr BP. The lake rose 7–12 m between 1300 and 900 cal yr BP, reached its present level around AD 1650, and within a few decades had risen an additional 12 m. Shortly thereafter, the lake established a northern outlet and fell to near its present level

Evidence for a Climate-Driven Hydrologic Regime Shift in the Canadian Columbia Basin

Water resources from the Columbia River Basin are intensely used for domestic, agricultural, industrial and hydroelectric generation needs. Water availability in the Pacific Northwest is influenced by several ocean–atmosphere modes of climate variability that occur in the Pacific Ocean. Climate change has the potential to alter these relationships and influence both the volume and timing of streamflow in the snowmelt-dominated tributaries to the Columbia River. Here, the historical influences of climate variability and recent climate warming on the volume and timing of streamflow for 40 tributary streams in the Columbia River Basin of Canada were evaluated. Regional relationships were found between streamflow and several Pacific Ocean climate indices, including the already established relationships with the Pacific Decadal Oscillation (PDO) and El Nino/Southern Oscillation (ENSO). However, in recent decades the statistical relationship between streamflow and climate indices has become weaker, which has implications for managers using these indices as decision-making tools. A comparison of the average annual streamflow for the cool PDO phase, which occurred from 1947 to 1976, to the more recent cool phase from 1999 to 2011 indicates a 11% decline across the Canadian portion of the basin. Removing the influence of these climate indices on historical streamflow reveals decreases in the residual streamflow beginning sometime in the 1980s. The potential role of increased temperatures on streamflow was investigated, and statistically significant relationships between decreased streamflow and increased temperatures in the summer months were found, particularly with the number of days over 18°C. The results suggest that climate change may be altering the historical relationship between climate indices and streamflow in the Canadian portion of the Columbia Basin

Increasing Ca2+ Deposition in the Western US: The Role of Mineral Aerosols

Considerable research has focused on the role of industrial emissions in controlling the acidity of precipitation; however, much less research has focused on the role of mineral aerosols emitted from soils. According to data published by the National Atmospheric Deposition Network (NADP), over the past 17 years Ca2+ deposition has increased over large regions of the US. A trend analysis to determine regions of significant change in Ca2+ deposition revealed statistically significant increases in three broad regions within the western half of the country: the inter-mountain west, the midwest, and the northwest. We evaluated potential changes in sources of calcium to the atmosphere including soil erosion, industrial emissions, forest fires, and sea-salt aerosols to determine the cause of rising atmospheric calcium deposition. Based on our evaluation, the most parsimonious explanation for increased Ca2+ deposition is an increase in mineral aerosol emissions from within the western US. This explanation is corroborated by independent evidence showing increases in the frequency of dust storms and low-visibility days across regions of the western US. Furthermore, our analysis indicates that the increase in mineral aerosol emissions is most likely due to (1) increased aridity and wind transport and (2) increased area and intensity of upwind human activities. Changes in atmospheric dust concentrations can have important ecological implications through the contribution of acid neutralizing capacity to both precipitation and regions of deposition. Thus increased dust emissions have the potential to ameliorate the detrimental effects of acid precipitation on terrestrial ecosystems, though dust may exacerbate the impacts of air quality on human health