East Of Lake Research Articles

Consistent solutions for simultaneous dynamic water, solute, stable isotope and radon balances to estimate average exchange fluxes between surface water bodies and groundwater

Many papers show that water, conservative solute, stable isotope and radon balances can be applied to the study of surface water – groundwater interaction. When undertaken simultaneously, such analysis provides an even more powerful method for estimating groundwater inflows and outflows, i.e. the exchange fluxes that for most people are hardest to estimate. The overarching objective of this paper is to provide practitioners with a consistent conceptual and simulation modelling framework with which to achieve a rapid initial understanding of surface water – groundwater interaction, as well as to guide the efficient and targeted acquisition of field data. This paper makes several important contributions. First, after an introduction that explains the complexities of groundwater flow patterns near surface water bodies, a set of general balance equations is developed using consistent terminology and notation. Second, after focusing on a simple conceptual model with steady groundwater inflow I, groundwater outflow O, precipitation P and ever-present evaporation E, analytical solutions are developed for transient and steady state conditions: one water balance solution is found to apply in all situations; solutions for the solute balance equation are developed for 23 different subcases; a transient balance equation for stable isotopes written in terms of 1+δ is found to apply in all situations; and a new transient solution for radon is found in terms of the upper incomplete gamma function. On the path towards developing the isotope balance equation, we present a rigorous approach, based on coupled nonlinear balance equations for abundant and rare isotope pairs (1H and 2H, then 16O and 18O), using isotope ratios and the fractions of each isotope. Third, we describe a Lake Water Balance Calculator (LWBC) written using GoldSim simulation software, a tool to help others to conduct the simultaneous analyses that we promote; we use GoldSim’s numerical methods to solve the general balance equations, we implement the analytical solutions to demonstrate that both GoldSim’s numerical methods and the analytical solutions are correct, and we also show that the 1+δ approximation is equivalent to the rigorous coupled equations, at least for heavy stable isotopes with very low abundance. Fourth, we describe field studies: we provide three examples of applications of LWBC to short-term studies of Perry Lakes East, Lake Jasper and Georgetown Billabong in Australia; we then describe WSIBal, a simulation model based on the same balance equations and describe its application to Lake Jasper over a 19-year period; finally, we describe R-WSIBal, which evolved from WSIBal, and explain its application to 2500 km of the Murray River in Australia.

Molecular phylogenetic analysis of the East Asian hemicultrine fishes (Teleostei: Cyprinidae: Xenocypridinae), with suggestions to their generic classification and redescription of the recently described species Hemiculter yungaoi Vasil'eva et al. 2022.

The hemicultrine fishes are a group of small-sized cyprinids, widely distributed but endemic to East Asian rivers and lakes. Till now, the taxonomic boundaries and relationships within this group remain poorly explored. In the present study, we study the phylogeny of this group, providing suggestions for classification of the hemicultrine group. Using two mitochondrial and three nuclear genes, and samples representing all genera, our results showed that the group consists of seven major lineages, of which four (Hemiculterella, Hainania, Pseudolaubuca, and Anabarilius) were monophyletic and three (Hemiculter, Toxabramis, and Pseudohemiculter) were not. Based on the phylogenetic tree, we redefined the genera. We revive the genus Siniichthys, which has three species, Siniichthys bleekeri, Siniichthys lucidus, and S. varpachovskii, that were previously treated as members of the genus Hemiculter but showed distant relationships to the genus Hemiculter in our phylogenetic tree. With the new results, a diagnostic key for clades of the hemicultrine group is provided. Furthermore, we provide more detailed information on diagnostic features of the recently described species Hemiculter yungaoi (Vasil'eva et al., 2022). This work will facilitate future systematic studies, pave the way for evolutionary studies, and provide valuable information for the urgent conservation of hemicultrine fishes.

An Initial Survey of Unionid Mussels in Lakes East of the Missouri River in South Dakota, USA

This study surveyed freshwater mussels (family Unionidae) in 116 lakes and reservoirs east of the Missouri River in South Dakota, USA, during 2017. Using two-person–hour/site timed searches, evidence of a total of 1789 mussels, including 1053 live mussels, was obtained from 50 waters. Nine species, from two different orders, were found in lakes and reservoirs throughout five of the six major river drainages east of the Missouri River. The native species observed included Giant Floater Pyganodon grandis, Fatmucket Lampsilis siliquoidea, Threeridge Amblema plicata, White Heelsplitter Lasmigona complanata, Wabash Pigtoe Fusconaia flava, Deertoe Truncilla truncata, and Pink Heelsplitter Potamilus alatus. Giant Floater was the most widespread and abundant species observed, representing 63.3% of the live mussels sampled. Two non-native species, Zebra Mussel Dreissena polymorpha and Chinese Basket Clam Corbicula fluminea, were also documented from three water bodies in the lower Missouri River drainage. Overall, mussel abundance was negatively correlated with lake water conductivity and positively correlated with turbidity. No significant correlations were observed between species abundance and water temperature, pH, dissolved oxygen, or substrate particle size.

Temporal and Spatial Comparison of Mercury Bioaccumulation in the Lower Trophic Levels of a Post-glacial Lake Food Web.

Total mercury (Hg) concentrations and carbon (δ13C) and nitrogen (δ15N) stable isotopes were quantified among aquatic invertebrate and sediment samples collected from Keuka Lake in New York's Finger Lakes region to evaluate temporal and spatial variability in Hg bioaccumulation and trophic ecology among these lower trophic levels. Hg concentrations ranged from 6.3 to 158.8ng/g (dry wt) across dreissenid mussel, zooplankton, and juvenile (< 10mm) and adult (≥ 10mm) mysid shrimp (Mysis diluviana) samples. Hg concentrations were higher in samples collected from the western basin in 2015 relative to those for samples collected from this basin in 2022 (p < 0.001). While no specific mechanisms could be identified to explain this difference, higher δ15N values for zooplankton collected in 2015 support conclusions regarding the role of zooplankton trophic status on Hg concentrations in these populations. Spatial patterns in Hg concentrations were of generally low variability among samples collected from the lake's east, west and south basins in 2022. Trophic positions as inferred by δ15N were represented by adult mysids > juvenile mysids > large zooplankton (≥ 500µm) > dreissenid mussels ≥ small zooplankton (64-500µm). Differences were evident among the regression slopes describing the relationships between sample Hg concentrations and δ15N values across the lake's three basins (p = 0.028). However, this was primarily attributed to high δ15N values measured in dreissenid mussels collected from the south basin in 2022. Biota sediment accumulation factors ranged from 0.2 to 2.3 and were highest for adult M. diluviana but mysid δ13C values generally supported a pelagic pathway of Hg exposure relative to benthic sediments. Overall, these results provide additional support regarding the contributions of lower trophic levels to Hg biomagnification in aquatic food-webs.

The records of 239+240Pu and 137Cs of global fallout in Lake East Dongting Sediments and Responses to watershed environmental changes

Plutonium-239 + 240 and 137Cs in the environment can usually be used to track the impact of nuclear activities on the environment, and have become important tools in environmental geochemical studies. In this study, nine sediment cores (E1-E9) in Lake East Dongting were collected and measured for the activity concentration of 239+240Pu, 137Cs and the atomic ratio of 240Pu/239Pu, and then their vertical distribution characteristics were analyzed. The results show that: the activity concentrations of 137Cs and 239+240Pu in Lake East Dongting ranged from 5.26 ± 0.43 to 28.6 ± 2.23 Bq kg−1 and 0.29 ± 0.02 to 1.37 ± 0.09 Bq kg−1, with an average of 7.48 ± 0.68 Bq kg−1 and 0.39 ± 0.03 Bq kg−1, respectively. The atomic ratios of 240Pu/239Pu are 0.168 ± 0.012–0.211 ± 0.015, which are basically consistent with the global atmospheric deposition. The vertical profiles of 137Cs and 239+240Pu in sediment cores show obvious single-peak distribution in E1-E6 and bimodal distribution in E7-E9. The results of sedimentation rates calculated by 137Cs and 239+240Pu method ranged from 0.59 cm y−1 to 1.99 cm y−1 with a mean of 1.18 cm y−1 and 0.61 cm y−1 to 2.18 cm y−1 with a mean of 1.26 cm y−1. The inventories of 137Cs and 239+240Pu in nine sediment cores are 5.87–10.8 kBq m−2 and 307–545 Bq m−2, which are about 8–14 and 9–15 times the inventory in the global average atmospheric deposition at the same latitude respectively. Comparing the results of the sedimentation rates and the inventories from different sampling points indicates that extreme climatic events and human activities have a significant impact on sediment environment of Lake East Dongting.

Temporal and Spatial Variability of Dust in the Urmia Basin, 1990–2019

The living conditions in the Urmia Basin (northwestern Iran) face significant challenges due to dust events. This study investigates the spatial and temporal characteristics of dust phenomena in the Urmia Basin using MERRA-2 data and observational data from Tabriz, Urmia, Sarab, and Mahabad over a 30-year period (1990–2019). The findings reveal that despite several fluctuations, the annual number of dusty days increased from the 1990s to the 2010s in the Urmia Basin. The maximum number of dusty days was found to predominantly occur in May (spring) and October (autumn), driven by two distinct mechanisms. In early autumn, developing synoptic systems associated with increased wind speeds can cause dust emission from dry land sources. Consequently, an increase in dust wet deposition, precipitation, dust surface concentration, and the number of dusty days occurs in October. In contrast, a sharp decrease in precipitation from April to May leads to drying soil and dust emission in May. Among the studied cities, Tabriz experienced the highest number of dusty days (728) due to the combined effects of cross-border and local dust sources. The highest dust column density and dust dry deposition in the south and east of Urmia Lake indicate the impact of declining water levels, which resulted in a dry lakebed as the primary local dust source. The MERRA-2 spatial distribution reveals that dust surface concentration, and the number of dusty days decrease similarly from the southwest to the northeast of the Urmia Basin as the distance from cross-border dust sources increases. A positive correlation is observed between the number of dusty days and MEERA-2 data, including dust surface concentration, dust dry deposition, column mass dust, and total aerosol extinction, with coefficients of 0.74, 0.71, 0.69, and 0.68, respectively.

Natural and anthropogenic factors regulating fluoride enrichment in groundwater of the Nansi Lake Basin, Northern China

Excess fluoride (F−) in groundwater can be hazardous to human health of local residents who rely upon it. Beside natural sources, anthropogenic input may be an additional source to be considered. Twenty surface water and 396 groundwater samples were collected from the Nansi Lake Basin, with hydrogeochemical and isotope techniques employed to clarify the spatial variability, source, and the natural and anthropogenic factors regulating the occurrence of high F− groundwater. The factors responsible for elevated F− levels in surface water and deep confined aquifers are discussed based on their hydraulic relationship. Also a conceptual model of F− enrichment with different aquifer systems is put forward based on the geomorphic units of the basin. The results show that F− concentration is between 0.1 and 6.9 mg/L in the west of Lake, while ranged from 0.03 to 1.74 mg/L in the east of Lake. The hydrogeological setting and lithology are the primary factor determining the provenance of high-fluoride groundwater in the basin. Fluoride mainly originated from the dissolution of fluorine-bearing minerals, and is affected by the alkaline groundwater environment, cation exchange, adsorption, and evaporation. The landforms on the east side of Nansi Lake are low hills and piedmont sedimentary plains, where the aquifers consist of karst fissure water and overlying porewater. High F− groundwater is not observed in this area due to its rapid flow and Ca2+-enriched hydrochemical characteristics. The anthropogenic input (such as fertilizer application on farms and illegal industrial pollutant discharge), contribute F− to groundwater in varying degrees, especially in the shallow aquifers east of the lake and in some parts west of the lake. This work is a clear example of how natural processes together with human activities can affect the chemical quality of groundwater, which is essential to safeguard the sustainable management of water resources in semi-arid areas.

Assessing Benthic Community and Water Quality as the Bioindicator of Environment in Semayang Lake East Kalimantan, Indonesia

Assessing Benthic Community and Water Quality as the Bioindicator of Environment in Semayang Lake East Kalimantan, Indonesia

Finger Millet- A Possible Source of Human Nourishment and Health

Accessible for a significantly lower cost than other items, finger millet, the primary crop in human nutrition is regarded as a healthful diet for low-income populations. In Africa's West, East, and Great Lakes Regions, it is a reliable source of food. Furthermore, native to Ethiopia, it can withstand drought well. The chemical makeup of various finger millet types is crucial in determining which has a high nutritional value. Ethiopian research on the crop's chemical makeup is, however, lacking. This analysis evaluates the nutritional benefits, overall health, and application of finger millet in value-added foods. Its product is one of the most significant and is widely grown in several locations in Ethiopia and Eritrea. This little millet provides an essential amino acid in the form of foodstuffs lacking in leucine, isoleucine, methionine, and phenylalanine. The polyphenol and fiber content are also useful for various health advantages, including antioxidant, anti-diabetic, anti-atheroclerogenic, and anti-tumorigenic actions. Generally speaking, these millets are crucial for many items and are also utilized as a healthful food for newborns when fermented. They are also recognized as a significant source of fiber for diabetes patients.

Geochemistry and fluxes of gases from hydrothermal features at Newberry Volcano, Oregon, USA

We present the chemical and isotopic compositions of gases and fluxes of CO2 from the hydrothermal features of Newberry Volcano, a large composite volcano located in Oregon's Cascade Range with a summit caldera that hosts two lakes, Paulina and East Lakes. Gas samples were collected from 1982 to 2021 from Paulina Hot Springs (PHS) on the shore of Paulina Lake, East Lake Hot Springs (ELHS) on the shore of East Lake, and Obsidian Flow Gas Seep (OFGS), an area of diffuse gas emissions. Surveys of CO2 flux were conducted in 2020 at OFGS (1400 m2) and East Lake (4.1 km2). Gases from all three sites were CO2-rich (≥79 mol% in dry gas) but showed considerable compositional variability over time due to interaction with ground and surface water. An increase in H2S concentrations and decline in CO2/H2S ratios in ELHS gases coincided with a drop in East Lake water level from 1999 to 2021. ELHS and OFGS gases were high in CH4 relative to PHS and the δ13C of CH4 values for ELHS gases (−72.2 and − 63.6 ‰) reflected a predominantly biogenic origin. The dominant source of N2 and Ar in PHS, ELHS, and OFGS samples was likely groundwater. Helium isotopic ratios (6.47 to 8.02 Rc/Ra) support a persistent source of magmatic He beneath Newberry caldera and consistently high values measured at OFGS and PHS relative to ELHS suggest distinct fluid flow paths from depth to the surface features. The δ13C of CO2 and CO2/3He values (−8.9 to −5.35 ‰ and 1.3 × 109 to 4.6 × 1010, respectively) measured in gases reflect contributions of CO2 from both mantle and crustal sources. Measured CO2 fluxes at OFGS and East Lake ranged from 1 to 8808 and < 1 to 364 g m−2 d−1, respectively. A CO2 emission rate of 0.5 t d−1 was calculated for OFGS. The CO2 emission rate estimated for East Lake was 30 t d−1 and when compared to prior estimates, reflects steady-state lake degassing. An enhanced geochemical monitoring plan, including annual sampling of gases at ELHS, OFGS, and PHS for geochemical analysis, installation of a continuous lake-level monitoring station at East Lake, and annual CO2 flux surveys at OFGS, would provide valuable background data and insights into any precursor volcanic activity. Integrating geochemical data with data from the real-time seismic and GPS network at Newberry Volcano could better resolve and interpret potential changes in its magma-hydrothermal system.

Monitoring Shoreline and Land Use/Land Cover Changes in Sandbanks Provincial Park Using Remote Sensing and Climate Data

Climate change-driven forces and anthropogenic interventions have led to considerable changes in coastal zones and shoreline positions, resulting in coastal erosion or sedimentation. Shoreline change detection through cost-effective methods and easy-access data plays a key role in coastal management, where other effective parameters such as land-use/land-cover (LULC) change should be considered. This paper presents a remotely sensed shoreline monitoring in Sandbanks Provincial Park, Ontario, Canada, from 1984 to 2021. The CoastSat toolkit for Python and a multilayer perceptron (MLP) neural network classifier were used for shoreline detection, and an unsupervised change detection framework followed by a postclassification change detection method was implemented for LULC classification and change detection. The study assessed the recent coastal erosion and accretion trends in the region in association with spatiotemporal changes in the total area of the West and East Lakes, the transition between LULC classes, extreme climate events, population growth, and future climate projection scenarios. The results of the study illustrate that the accretion trend apparently can be seen in most parts of the study area since 1984 and is affected by several factors, including lake water-level changes, total annual precipitations, sand movements, and other hydrologic/climatic parameters. Furthermore, the observed LULC changes could be in line with climate change-driven forces and population growth to accelerate the detected accretion trend in the East and West Lakes. In total, the synergistic interaction of the investigated parameters would result in a greater accretion trend along with a lower groundwater table amid even a low carbon scenario. The discussed findings could be beneficial to regional/provincial authorities, policymakers, and environmental advocates for the sustainable development of coastal communities.

Structure of the Crustal Magmatic System in the Geysers-Clear Lake Area (Northern California) Imaged by Adjoint-State Travel-Time Tomography

Abstract The Clear Lake volcanic field (CLVF) in northern California powers the world’s largest geothermal power plant, the Geysers Geothermal Complex. Volcanic-type earthquakes, hot springs, and seepage of volcanic gas suggest possible volcanic eruptions in the future. In this study, we apply a recently developed adjoint-state travel-time tomography method to high-quality manually picked P- and S-wave travel-time data to create 3D crustal VP and VS models for the Geysers-Clear Lake area. The adjoint-state travel-time tomography method has advantages of computational efficiency, ease of parallel implementation, and high accuracy in dealing with complex media. Strong velocity heterogeneities are revealed in the Geysers-Clear Lake area and its surrounding regions. Within the overall high VP, high VS Coast Ranges, a low VP, low VS anomaly is imaged beneath Mount Hannah, which indicates the existence of a large magma chamber. Our tomographic results suggest a simplified three-layer magmatic model beneath the CLVF: the upper layer (&amp;lt;7 km) consists of some intrusions of silicic magma from beneath Mount Hannah to the Geysers Geothermal Field in the southwest and to the Wilbur Springs area east of Clear Lake; the median layer includes the main body of the magma chamber at 5–13 km in depth and in the shape of an oblate ellipsoid; and the lower layer includes some mafic intrusions and molten or partially molten volcanic rocks from the upwelling mantle. The detailed velocity heterogeneities revealed by the newly picked travel-time data with the adjoint-state travel-time tomography method provide necessary constraints on seismogenic, volcanic, and geothermal processes in the Geysers-Clear Lake area, which are also useful for the mitigation of geologic hazards in northern California.

Deep Learning-Based Automatic Extraction of Cyanobacterial Blooms from Sentinel-2 MSI Satellite Data

Cyanobacterial harmful algal blooms (CyanoHABs) in inland water have emerged as a major global environmental challenge. Although satellite remote sensing technology has been widely used to monitor CyanoHABs, there are also some automatic extraction methods of CyanoHABs based on spectral indices (such as gradient mode, fixed threshold, and the Otsu method, etc.), the accuracy is generally not very high. This study developed a high-precision automatic extraction model for CyanoHABs using a deep learning (DL) network based on Sentinel-2 multi-spectral instrument (MSI) data of Chaohu Lake, China. First, we generated the CyanoHABs “ground truth” dataset based on visual interpretation. Thereafter, we trained the CyanoHABs extraction model based on a DL image segmentation network (U-Net) and extracted CyanoHABs. Then, we compared three previous automatic CyanoHABs extraction methods based on spectral index threshold segmentation and evaluated the accuracy of the results. Based on “ground truth”, at the pixel level, the F1 score and relative error (RE) of the DL model extraction results are 0.90 and 3%, respectively, which are better than that of the gradient mode (0.81,40%), the fixed threshold (0.81, 31%), and the Otsu method (0.53, 62%); at CyanoHABs area level, the R2 of the scatter fitting between DL model result and the “ground truth” is 0.99, which is also higher than the other three methods (0.90, 0.92, 0.84, respectively). Finally, we produced the annual CyanoHABs frequency map based on DL model results. The frequency map showed that the CyanoHABs on the northwest bank are significantly higher than in the center and east of Chaohu Lake, and the most serious CyanoHABs occurred in 2018 and 2019. Furthermore, CyanoHAB extraction based on this model did not cause cloud misjudgment and exhibited good promotion ability in Taihu Lake, China. Hence, our findings indicate the high potential of the CyanoHABs extraction model based on DL in further high-precision and automatic extraction of CyanoHABs from large-scale water bodies.

Selenium Distribution and Trophic Transfer in the Periphyton-Benthic Macroinvertebrate Food Chain in Boreal Lakes Downstream from a Milling Operation.

Selenium (Se) is an essential micronutrient with a narrow essentiality-toxicity range known to bioaccumulate in aquatic food webs. Selenium uptake and trophic transfer at the base of aquatic food chains represent a great source of uncertainty for Se risk assessment. The goal of the present study was to investigate Se distribution in water and sediment and its subsequent transfer into the periphyton-benthic macroinvertebrate (BMI) food chain in boreal lakes downstream from a Saskatchewan uranium mill. In particular, the present study aimed to assess potential differences in Se bioaccumulation patterns by BMI taxa to contribute to the current knowledge gap. During summer 2018 and 2019, water, sediment, periphyton, and BMI were sampled at two sites in Vulture Lake, seven sites in McClean Lake east basin, and one reference site in McClean Lake west basin. Periphyton and BMI taxa were sampled with artificial substrates (Hester-Dendy) deployed for 5 weeks in 2018 and 7 weeks in 2019; BMI were sorted into the lowest practical achievable taxonomic level and analyzed for total Se concentrations. At the diluted effluent exposure sites, Se concentrations in BMI ranged from 1.3 to 18.0 µg/g dry weight and from 0.3 to 49.3 µg/g dry weight in 2018 and 2019, respectively, whereas concentrations ranged from 0.01 to 3.5 µg/g dry weight at the reference site. Selenium concentrations in periphyton and some BMI taxa sampled near the effluent diffuser (Se < 1 µg/L) reached levels comparable to higher effluent exposure sites (Se > 2 µg/L). Despite differences in Se bioaccumulation among BMI taxa, an approximately one-to-one trophic transfer ratio was observed for benthic primary consumers and benthic predatory taxa. Environ Toxicol Chem 2022;41:2181-2192. © 2022 SETAC.

Occurrence of polycyclic aromatic hydrocarbons in the estuarine sediments of the Taihu Lake and their associated toxic effects on aquatic organisms

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous toxic organic pollutants in the natural environment that are strongly associated with socioeconomic activities. Exploring the distribution, sources, and ecological toxicity of PAHs is essential to abate their pollution and biological risks. Sixteen priority PAHs in different lakeside city estuarine sediments in northern Taihu Lake in China were determined by gas chromatography-mass spectrometry. Results showed that total concentrations of PAHs (ΣPAHs) ranged from 672.07 to 5 858.34 ng g -1 , with a mean value of 2 121.37 ng g -1 . High-molecular-weight PAHs (4–6 rings) were dominant, accounting for 85% of the ΣPAHs detected. Due to the barrier of gate/dam in the estuarine area, the concentrations of PAHs in the sediments were significantly different between the river mouth and lake side. Changes in total organic carbon (TOC) content and the spatial distribution of PAHs in the sediments were consistent. Sediment pollution assessment explored using the fuzzy evaluation model indicated 75% of slight PAH pollution. Some estuarine sediments (22%) concentrated in the east of Wuli Lake were moderately or heavily polluted. The PAHs may lead to occasional detrimental biological consequences in the area. Diagnostic ratios and principal component analysis-multiple linear regression suggested vehicle emission and natural gas combustion as the primary PAH contributors (81%).

Delineating Effluent Exposure and Cumulative Ecotoxicological Risk of Metals Downstream of a Saskatchewan Uranium Mill Using Autonomous Sensors.

There is increasing interest in using autonomous sensor technology to monitor aquatic ecosystems in real time and in employing such monitoring data to perform better ecological risk assessments. At seven locations in McClean Lake in northern Saskatchewan (Canada) that received diluted uranium milling effluent, we deployed sensor units to track effluent distribution and help predict potential biological effects on aquatic invertebrates. Water was also collected from each location on multiple occasions to measure major ions, dissolved metals, and routine water quality, and sediment was sampled to analyze total metals. The ecotoxicological risk to aquatic invertebrates was estimated using hazard quotients (HQs). The cumulative risk was estimated by summing the individual HQs, and the major ions risk was based on total osmolarity. The results indicated temporal and spatial variations in effluent exposure based on sensor electrical conductivity (EC) measurements in the McClean Lake East Basin. Individual HQs for water ranged from "moderate" (0.40-0.69) to "very high" (greater than 1) for silver, cadmium, arsenic, selenium, mercury, iron, and thallium. At all sites, major ions risk was less than 1. Individual HQs for sediment were "moderate" (0.40-0.69), "high" (0.7-0.99), and "very high" (greater than 1) for vanadium and cadmium. The cumulative risk in water and sediment for all metals combined was greater than 1 at some sites in Vulture Lake (which discharged into McClean Lake) and in McClean Lake itself. A more detailed estimation of the risks for aqueous selenium and arsenic (the only two metals that had good correlation with sensor EC data) indicated that their 90th percentile HQ values were less than 1 in McClean Lake, suggesting that these contaminants of concern do not represent a significant direct risk to aquatic invertebrate communities. Environ Toxicol Chem 2022;41:1765-1777. © 2022 SETAC.

Report of the Eighty-Third Annual Meeting: San Diego, California October 14–16, 2021

Report of the Eighty-Third Annual MeetingSan Diego, California October 14–16, 2021 Liz Ridder, Atsushi Nara, and Yolonda Youngs (bio) After a one-year meeting hiatus due to Covid-19, APCG members gleefully gathered, in-person and online, for the Eighty-Third Annual Meeting at San Diego State University (SDSU). Much to the organizers' relief, 149 people pre-registered for the meeting, with 66 online and 83 in-person attendees, plus several folks who registered in person. This year's meeting was unique for many reasons and was aptly themed "Geographies of Transition." Organizers Atsushi Nara, Liz Ridder, and Yolonda Youngs, each from a different California State University (CSU)—SDSU, CSU San Marcos, and CSU San Bernardino—banded together to bring a hybrid meeting format to APCG without losing long-standing APCG meeting traditions. This "experimental" year was part of a larger initiative organized by the AAG and its Climate Action Task Force as part of their Regions Connect: A Joint Climate Forward Initiative, which may lead to larger regional meetings in the future, to reduce carbon emissions of AAG events. As part of meeting registration, attendees could virtually attend the streaming and recorded sessions of the Applied Geography Conference and the AAG Regional Division meetings of the Southwest (SWAAG), East Lakes, West Lakes, New England-St. Lawrence Valley (NESTVAL), and Great Plains/Rocky Mountains. Concurrent paper and poster sessions took place Thursday and Friday in the Conrad Prebys Aztec Student Union. Also known as the Union, the building opened in 2013, replacing the first CSU student union, the Aztec Center. The construction of the Union reused and recycled approximately eighty percent of the Aztec Center's materials, and the building is LEED Double Platinum Certified. The recent renaming of one of the meeting rooms created momentary confusion until a clever geographer updated the door sign to match the new name printed in the meeting program and campus maps. Once [End Page 163] meeting room locations were sorted, thirty-one in-person and seventeen virtual papers and eight posters were presented by authors from Arizona, California, Michigan, Washington, Oregon, Nevada, Florida, Alabama, and Germany. On Thursday afternoon, Keynote Speaker Dr. Marilyn Raphael, Professor, UCLA, Director of the UCLA Institute of the Environment and Sustainability, and Vice President of the AAG, presented "Antarctic Sea Ice—How Important Is It?" highlighting regional patterns of spatial, spectral, and temporal variability, including the timing of advance and retreat, and positive and negative growth trends of sea ice throughout the Antarctic. These patterns are likely related to Antarctica's geography and the influence of the ocean and atmosphere, which are expected to change as the atmosphere continues to change. Friday's Keynote Lecture by Dr. Park Williams continued discussions on "Geographies of Transition" and the impacts of climate change in his talk, "The effect of climate change on water, wildfire, and life across North America." This year's conference also featured two special sessions on Friday afternoon. Dr. Atsushi Nara organized and moderated a hybrid-mode interactive workshop to identify perceptions about the skills and knowledge to succeed in geocomputation-related careers. The project is an NSF-funded collaboration through an Encoding Geography Researcher-Practitioner Partnership (RPP) led by AAG, SDSU, San Diego Mesa Community College, Sweetwater High School Union District, Texas State University, and UC Riverside. Dr. Dan Arreola organized and moderated a discussion panel titled "Donald W. Meinig's Southwest at Half-Century, A Reflection and Appreciation." Former Meinig students and scholars of his work Bill Wyckoff, Craig Colten, Paul Starrs, and Richard Nostrand shared their perspectives on Meinig's influence on their interpretations of the Southwest and the formation of their geographical perspectives. Social events such as the Women's Network and Graduate Student lunches provided opportunities to celebrate students and connect with new colleagues and old friends. The Thursday-night reception on the Union's 3rd Floor Terrace included wonderful food and drink, supplemented [End Page 164] by a spectacular view and live music from the courtyard below. The highlights of Friday night's awards banquet were the numerous student awards for outstanding papers and posters and student travel scholarships, presenting Chris Lukinbeal with the Distinguished Service...

Trachyandesite of Kennedy Table, its vent complex, and post–9.3 Ma uplift of the central Sierra Nevada: Reply

We thank Emmanuel Gabet for his interest in our work on the Trachyandesite of Kennedy Table and for the opportunity to more fully explain our methods. We (Hildreth et al., 2021) claimed that various lines of evidence from the lava flow strongly support ∼1° of tilting of the central Sierra Nevada since 9.3 Ma. Gabet (2021) stated, “However, their analyses rely on inferences and assumptions that are not supported by field evidence.” First, he addressed the issue of whether the sinuous lava-flow remnants east of Millerton Lake are fortuitously shaped erosional remnants of a planar lava flow, or whether they are fossilized meanders of the paleo−San Joaquin River, which he terms to be our “interpretation.” We strongly disagree with this characterization. In Hildreth et al. (2021), we treated the meander question as a hypothesis to be tested using topographic data.

Grain size characteristics of the sand silt layers in the ancient delta of the dried Lop Nur lake (east Tarim Basin) and their environmental implications

Grain size characteristics of the sand silt layers in the ancient delta of the dried Lop Nur lake (east Tarim Basin) and their environmental implications

A Phylogeographic Contact Zone for Arctic Grayling in Alberta, Canada

AbstractArctic Grayling Thymallus arcticus are a salmonid with a Holarctic distribution, extending from northeastern Eurasia through northwestern North America. Throughout their range, Arctic Grayling face a number of threats, including angling mortality, habitat fragmentation and loss, and climate change. Thus, there is a need to protect the species through targeted management actions. Genetic information can assist in determining the appropriate scale for these actions through the description of designatable units. Here we use newly collected mitochondrial DNA sequence data to assess the phylogeographic structure of Arctic Grayling in Alberta, Canada, and link these with previously collected mitochondrial and microsatellite data to determine how many designatable units may exist across Canada. Our assessment of 831 base pairs of sequence data in 96 individuals found two deeply divergent lineages in Alberta. When combined with 22 previously collected sequences, our results highlight that Alberta is a contact zone for the observed lineages of Arctic Grayling in North America. A reassessment of nine microsatellites that were genotyped in 1,116 individuals further highlighted interbasin divergence, likely the result of historical processes. Given the divergence and geographic distribution of the genetic diversity, Arctic Grayling in Canada merit consideration for separate designatable units in future species status assessments and management plans. Continuing research should attempt to expand sampling geographically (e.g., regions east of Great Slave Lake and along the Arctic coastline) to clarify possible colonization routes and add to or synthesize the work on Arctic Grayling behavior, morphology, and life history to address the limited understanding of local adaptions within this species.