Lake Group Research Articles

Rapidly expanding lake heatwaves under climate change

Lake heatwaves—prolonged periods of hot surface water temperature in lakes—have recently been shown to increase in intensity and duration, with numerous potential implications for aquatic ecosystems. However, an important physical attribute of lake heatwaves that has not yet been investigated is their spatial extent, and how it varies within a warming world. Here, we show that the spatial extent of lake heatwaves, defined as contiguous regions within a lake that simultaneously experience extreme warm conditions, is increasing in the largest group of freshwater lakes on Earth, The Laurentian Great Lakes. We show that the maximum spatial extent of lake heatwaves is sensitive to inter-annual variations in winter ice cover and the timing of stratification onset in spring. Notably, we find that a lengthening of the warm summer season and, in turn, an overall increase in surface water temperature, stimulates the development of larger lake heatwaves. On average, our results suggest that the mean spatial extent of lake heatwaves has increased two-fold since 1995. We anticipate this rapid expansion of lake heatwaves to have widespread implications for heat-related impacts on aquatic species.

Food availability and temperature optima shaped functional composition of chironomid assemblages during the Late Glacial–Holocene transition in Northern Europe

Non-biting midges (Chironomidae) are the most diverse and abundant invertebrate group in boreal lakes and are strongly responsive to climate change, thus they are a valuable palaeoecological proxy for studying aquatic biodiversity response in the face of climate change. Here, we aim to decipher the influence of climate-induced changes on temporal patterns in chironomid assemblages. We apply a novel approach combining traditional taxon-based analysis and species-trait framework to subfossil chironomid assemblages in a sediment core covering the Late Glacial–Holocene transition in Northern Europe. We produce pollen-based July and January temperature reconstructions to characterize past climate fluctuations that show a distinct Early Holocene warming for continuous 1700 years with considerably greater warming in winter (ca. 10 °C) than summer (ca. 4 °C) temperature. Overall, chironomid taxonomic changes were mainly induced by the temperature tolerances and optima of species, as temporal dynamics showed agreement with temperature reconstructions. Our results suggest that vegetation dynamics could also play a role in structuring chironomid assemblages by selecting taxa with the highest ability to exploit available food resources, thus potentially confounding chironomid-based summer climate reconstructions. We demonstrate that the study of the hidden chironomid functional composition could help to identify secondary drivers and thus strengthen the reliability of climate reconstruction based on subfossil chironomids.

Shale-hosted biota from the Dismal Lakes Group in Arctic Canada supports an early Mesoproterozoic diversification of eukaryotes

AbstractThe Mesoproterozoic is an important era for the development of eukaryotic organisms in oceans. The earliest unambiguous eukaryotic microfossils are reported in late Paleoproterozoic shales from China and Australia. During the Mesoproterozoic, eukaryotes diversified in taxonomy, metabolism, and ecology, with the advent of eukaryotic photosynthesis, osmotrophy, multicellularity, and predation. Despite these biological innovations, their fossil record is scarce before the late Mesoproterozoic. Here, we document an assemblage of organic-walled microfossils from the 1590–1270 Ma Dismal Lakes Group in Canada. The assemblage comprises 25 taxa, including 11 morphospecies identified as eukaryotes, a relatively high diversity for this period. We also report one new species,Dictyosphaera smauginew species, and one unnamed taxon. The diversity of eukaryotic forms in this succession is comparable to slightly older assemblages from China and is higher than worldwide contemporaneous assemblages and supports the hypothesis of an earlier diversification of eukaryotes in the Mesoproterozoic.

The consecutive lake group water storage variations and their dynamic response to climate change in the central Tibetan Plateau

Lakes on the Tibetan Plateau (TP) are a reliable indicator of local and global climate changes. Surveying lake water storage (LWS) and understanding the causes of lake variations are crucial to regulate water resources and protect local ecology. However, the lake bathymetric survey and the analysis of consecutive lake changes were absent on the TP. In this study, we investigated the LWS for seven lakes in the central TP and estimated their water storage variations during the period of 1976–2018 by utilizing long-term time series Landsat images and bathymetric data. Then, the driving factors of lake water storage variations were also analyzed based on the data of the meteorological station. The results suggested that the LWS of the seven lakes (Co Nag, Daru Co, Dung Co, Pung Co, Co Ngoin, Bam Co, and Neri Punco) in the central TP expanded by 2.54 km3 (22.12%) from 1976 to 2018, with total lake area increased by 183.42 km2 (22.73%), especially experienced obviously increasing trend between 1997 and 2006. The growth of LWS between 1997 and 2006 explained 70.63% of the net increase during the whole period. While the correlation analysis of LWS and climate change revealed that temperature, precipitation, and evaporation all had impacts on the changes of LWS, temperature and precipitation dominated the main role for the expansion of these lakes during the period of 1997–2006, and LWS had approximately 3 years of lag time in response to precipitation. We also found that the time of the abrupt increase of LWS was probably associated with the step change point of annual precipitation.

It's complicated: Heterogeneous patterns of genetic structure in five fish species from a fragmented river suggest multiple processes can drive differentiation.

Fragmentation of river systems by dams can have substantial genetic impacts on fish populations. However, genetic structure can exist naturally at small scales through processes other than isolation by physical barriers. We sampled individuals from five native fish species with varying life histories above and below a dam in the lower Boardman River, Michigan, USA, and used RADseq to investigate processes influencing genetic structure in this system. Species assessed were white sucker Catostomus commersonii, yellow perch Perca flavescens, walleye Sander vitreus, smallmouth bass Micropterus dolomieu, and rock bass Ambloplites rupestris. We detected significant differentiation within each species, but patterns of population structure varied substantially. Interestingly, genetic structure did not appear to be solely the result of fragmentation by the dam. While genetic structure in yellow perch and walleye generally coincided with “above dam” and “below dam” sampling locations, samples from our other three species did not. Specifically, samples from rock bass, smallmouth bass, and, to a much lesser extent, white sucker, aligned with a putative Great Lakes (GL) group that contained mostly individuals sampled below the dam and a putative Boardman River (BR) group that contained individuals sampled both above and below the dam, with some evidence of admixture among groups. We hypothesize that the GL and BR groups formed prior to dam construction and our samples largely represent a mixed stock that was sampled sympatrically outside of the spawning season. Support for this hypothesis is especially strong in smallmouth bass, where GL fish were 151 mm smaller than BR fish on average, suggesting a potential ontogenetic habitat shift of young GL fish into the lower river for feeding and/or refuge. Our study illuminates the complex dynamics shaping genetic structure in fragmented river systems and indicates that conclusions drawn for a single species cannot be generalized.

Quantifying Ecosystem Services of High Mountain Lakes across Different Socio-Ecological Contexts

Mountain lakes are highly sensitive to global change, requiring sustainable management strategies that support crucial ecosystem services (ES). However, small mountain lakes are rarely in the focus of ES assessments, and indicators are potentially lacking. Therefore, this study aimed at comprehensively assessing key ES of 15 study lakes located in two regions in the European Alps. We involved local stakeholders and experts to identify important ES. We quantified eight ES in non-monetary terms, using 29 indicators based on limnological, spatial and socio-economic data. Finally, we evaluated ES in relation to the socio-ecological context of the study lakes. The most important ES included surface water for non-drinking purposes, maintaining populations and habitats, outdoor recreation, aesthetic value, entertainment and representation, scientific research, education as well as existence, option, or bequest value. Quantitative results indicate varying levels of ES across the study lakes. Based on 12 different socio-ecological variables, we identified four groups of lakes differing also in five ES. Maintaining populations and habitats, aesthetic value as well as existence, option or bequest value were rather independent from the socio-ecological context. Our findings contribute to a deeper understanding of ES of mountain lakes, also supporting the development of sustainable management strategies in mountain regions.

Deposition models for the widespread Eocene bedded halite in China and their implications for hydrocarbon potential of salt-associated mudstones

A group of Eocene saline lakes were developed in the middle latitudinal arid zone across East Asia. In these lakes, bedded halite and laminated mudstones were alternately deposited in lake centers, leading to a long-standing controversy about their depositional water conditions. Here we selected three representative Eocene saline lakes, spanning east to west over China, and made comparisons of their minerology and minor element abundances. Minor elements of solid halite can reflect the relative abundances of impurities: quartz (Zr, Hf), K-silicates (Rb, Th, Cs, Pb, Zn), clays (Co, Cr, V, Ni, Li), carbonates (Sc, Cu, Sr), sulphates (U, Ba), and organic matter (Mo, Cu, V, Ni), and thus can indicate depositional environments. Halite in the east Dongpu Depression is mainly composed of chevron crystals and comparatively enriched in most elements. Halite in the central Qianjiang Depression mainly consists of tightly-cemented coarsely-crystalline mosaics and is depleted in most elements, except for elements Cu, V, and Ni. Whereas halite in the west Mangya Depression underwent syndepositional and burial recrystallization, and contains moderate abundances of most minor elements, with significant enrichments in elements Sc, Cu, and V. Saline lakes in the three depressions represent three typical continental settings for bedded halite deposition: a stratified shallow-water lake in the Dongpu Depression, a stratified deep-water lake in the Qianjiang Depression, and a mixed shallow-water lake in the Mangya Depression. These depositional models provide implications about the hydrocarbon exploration potential of salt-associated mudstones: highest in the stratified deep-water lakes, medium in the stratified shallow-water lakes and lowest in the mixed shallow-water lakes.

Planning and Responding to a Petrochemical Disaster in the North American Inland Seas

The Great Lakes represent the largest group of freshwater lakes in the world along a 1,500 mile international boundary between the United States and Canada. A source of drinking water for 35 million people and a hub of unique biodiversity, a major petrochemical spill would be devastating. With the increase in pipeline activity due to regional tar sands drilling and the navigationally challenging waterways hosting an increasing stream of petrochemical commerce, risk to the Lakes is higher than ever. Given the Lake's closed-system nature and their geographic remoteness relative to current US and Canadian government and private sector assets, the current response posture is inadequate. As the primary maritime spill response agency in the United States, the US Coast Guard retains the mantle of prevention and planning for a Great Lakes petrochemical disaster. This paper seeks to examine the historic, current, and future states of the Great Lakes' oil-spill risk, in light of increased maritime commerce and recent spill “near-misses” regarding submerged pipelines in the Straits of Mackinac. The US Congress and the US Coast Guard have identified that the Great Lakes are not prepared for a large scale spill. Current resourcing levels and technology are insufficient, especially given the challenge of responding while the Lakes are frozen for a substantial portion of the year. With resources focused on the prospect of disaster in salt water regions, the “inland seas” of the Great Lakes receive too little attention. After identifying the evolution of Great Lakes spill prevention and response policy, this paper will apply the Gulf of Mexico Deepwater Horizon spill as a case study into what spill response would look like on the Great Lakes. Given the authors' expansive experience as an operator during that historic spill and current commander of one of two US oil spill response assets in the Great Lakes, this paper will also identify remaining challenges to an effective spill response policy, and conclude with recommendations on how to tackle the response issues identified. The US Congress recently established the US Coast Guard's National Center of Expertise for the Great Lakes and one of their primary tasks is to analyze the effect of a spill in freshwater and develop an appropriate response plan. By attempting to identify critical gaps, this paper seeks to advance government and industry's ability to posture the region swiftly in the face of a growing threat and assist in the Center's work.

ОСОБЕННОСТИ ФЛОРИСТИЧЕСКОГО СОСТАВА И ХАРАКТЕР ЗАРАСТАНИЯ МАЛЫХ НЕПРОТОЧНЫХ ОЗЕР НАРОЧАНСКОЙ ГРУППЫ (БЕЛОРУССИЯ)

The flora of small non-flowing lakes of the Narach lake group located on the territory of the Narachanski National Park (Belarus, Minsk region, Myadelsky district) was studied. The taxonomic composition of the flora numbering 126 species of vascular plants belonging to 85 genera from 42 families was revealed. Three plant species which are included in the list of protected taxa in Belarus were found – Liparis loeselii (L.) Rich. (Lake Shestakovo), Aldrovanda vesiculosa L. (Lake Shestakovo) and Isoëtes lacustris L. (Lake Beloe). Based on the annotated list of species presented in the work, taxonomic, geographical, ecological-coenotic and ecobiomorphological analyzes of the flora of water bodies were performed. According to the taxonomic and environmental structure, the flora of the studied lakes is shown to be traditional for this territory. The differences in the flora of the studied lakes are mainly due to their trophic status and, to a lesser extent, due to the diversity of biotopes and the nature of the anthropogenic load. Information on the nature of overgrowing of these water bodies is provided.

Optimal Operation of Floodwater Resources Utilization of Lakes in South-to-North Water Transfer Eastern Route Project

In order to meet the demand of emergency water supply in the northern region without affecting normal water transfer, considering the use of the existing South-to-North Water Transfer eastern route project to explore the potential of floodwater resource utilization in the flood season of Hongze Lake and Luoma Lake in Jiangsu Province, this paper carried out relevant optimal operating research. First, the hydraulic linkages between the lakes were generalized, then the water resources allocation mode and the scale of existing projects were clarified. After that, the actual available amount of flood resources in the lakes was evaluated. The average annual available floodwater resources in 2003–2017 was 1.49 billion m3, and the maximum available capacity was 30.84 billion m3. Then, using the floodwater resource utilization method of multi period flood limited water levels, the research period was divided into the main flood season (15 July to 15 August) and the later flood season (16 August to 10 September, 11 September to 30 September) by the Systematic Clustering Analysis method. After the flood control calculation, the limited water level of Hongze Lake in the later flood season can be raised from 12.5 m to 13.0 m, and the capacity of reservoir storage can increase to 696 million m3. The limited water level of Luoma Lake can be raised from 22.5 m to 23.0 m (16 August to 10 September), 23.5 m (11 September to 30 September), and the capacity of reservoir storage can increase from 150 to 300 million m3. Finally, establishing the floodwater resource optimization model of the lake group with the goals of maximizing the floodwater transfer amount and minimizing the flood control risk rate, the optimal water allocation scheme is obtained through the optimization algorithm.

Novel responses of diatoms in neotropical mountain lakes to indigenous and post-European occupation

How Indigenous peoples and European settlers transformed terrestrial ecosystems in the Americas is well evidenced in the literature, but far less is known about how aquatic ecosystems changed. This study examined diatom records from sediment cores from paleoclimate studies in mountain lakes of Guatemala, Panama, and Colombia, in order to clarify the long-term human influences on the ecology of these lakes. We focused on two aspects of beta diversity in identified diatom zones: species turnover and variation in relative abundances of species. All records displayed a single diatom zone or cluster of zones with assemblages that had no close analogues in the past. The ages of these distinctive assemblages varied from post-European to 5000 cal yr BP. Most novel assemblages comprised moderately motile, non-planktonic, single-celled diatoms, associated with disturbed, productive environments. Archaeological data and pollen records pointed to the onset of intensification of human activities as the main driver behind the changes in diatoms. Maximum depth exerted control on how diatom communities responded to anthropogenic stressors. In shallower lakes, diatom assemblages transitioned gradually over time into their current novel composition. In deeper lakes, assemblages displayed slight fluctuations before shifting to their current condition. Differences between the two lake groups likely resulted from a more complete water-column mixing and higher rates of nutrient cycling in the shallow lakes, which led to a more rapid response of the diatoms to environmental changes. The shift to novel recent diatom assemblages suggests that these lakes now display ecosystem characteristics with no past analogues, and that they have lost their capacity to resist change or recover from stressors, jeopardizing the future of mountain water resources.

Phylogenetic diversity and dominant ecological traits of freshwater Antarctic Chrysophyceae

Previous studies conducted in summer in the lakes at Hope Bay (Antarctic Peninsula) between 1991 and 2007 showed a large numerical contribution of flagellated Chrysophyceae to the phytoplankton communities, particularly in the oligotrophic lakes, as evidenced by light microscopy observations and molecular fingerprinting. Given the ecological relevance of this group in these Antarctic microbial foodwebs, we carried out further molecular analyses (clone libraries and 18S Illumina high throughput sequencing) to characterize their phylogenetic diversity. The results of this study significantly increased the retrieved Chrysophyceae biodiversity. Clone libraries in two selected lakes (one oligotrophic and one mesotrophic) yielded 12 different chrysophycean OTUs, whereas 81 Swarm OTUs were recovered from six lakes using Illumina HiSeq. With the combination of both methods, we observed sequences of all the chrysophyte known clades, although most of the diversity belonged to Clade D, a group comprising mixotrophic and heterotrophic species. The percentage of reads for this clade in Illumina HiSeq ranged from 30% to 96% of the total Chrysophyceae reads. Based on experiments and observations, we also describe the main ecological traits of this group: the dominant taxa were small pigmented flagellates, well adapted to survive in oligotrophic systems, sometimes abundant under ice-cover subjected to low light intensities, and that have phagotrophic behavior. The used combination of methods allowed us to characterize the biodiversity and ecology of the Chrysophyceae, the dominant phytoplankton group in the oligotrophic lakes of this Maritime Antarctic region.

Biogeochemical peculiarities of accumulation of chemical elements by plants of the Svydovets Massif of the Ukrainian Carpathians


 
 
 he objective of the paper was determining biogeochemical peculiarities of ac- cumulation of chemical elements (Mn, Ni, Сo, V, Cr, Zr, Cu, Pb, Zn, Ba, P) by wild-grow- ing shrubs (stems and leaves) – bog bilberry (Vaccіnium uliginоsum), European blueberry (Vaccinium myrtillus L.), alpine juniper (J. communis subsp. alpina); perennial herbaceous plants (flowers and leaves) – common tormentil (Potentіlla erecta (L.) Hampe), willow gentian (Gentiana asclepiadea), true sedges (Carex); and trees (needles) of European silver fir (Abies alba) on nine plots in the Svy- dovets Massif of the Ukrainian Carpathians. The results we obtained based on field surveys (selection of samples of soil and vegeta- tion) and interpretation of their analysis allowed us to determine the total regional background of chemical elements in soils and ash of plants using emission spectral analysis. We assessed the total concentration of chemical elements in soils of the plots (least to highest): the Apshynets Ridge – the Herashaska Polonyna – Drahobratske Lake – the Svydovets stream – Apshynets Lake – Herashaske Lake – the Zhuravlyne Bog – Vorozheske Lake (group of small lakes) – Vorozheske Lake (large) and determined the dependence on type of soil and pH. We determined that for wild-growing herbaceous plants the biogeochemical activity of species increases in the following sequence: true sedges - willow gentian - common tormentil; for wild-growing shrubs (bog bilberry, European blueberry, alpine juniper) such a sequence is impossible to determine due to the great difference between the values on different plots. We determined the role of each plant as medicinal for treating microelement deficiency in Cu, Zn, Co. We determined that in the plot of the Herashaska Polonyna, the needles of alpine juniper contain a maximum amount of Zn and Co, the needles and leaves of bog bilberry – Cu, Zn, Co; the flowers and leaves of common tormentil by Apshynets Lake and European silver fir near the area of the Svydovets stream – Cu. We calculated the daily dose of each element according to species of plants to overcome microelementosis. The results of biogeochemical surveys may be the basis for determining and recommending plants as medicinal, and also of geochemical and biogeochemical monitoring studies.
 
 

Paleolatitude and tectonic rotations of the Early Carboniferous Fountain Lake Group, Cobequid Highlands, Nova Scotia, Canada

The ca. 355 Ma Fountain Lake Group in the Cobequid Highlands of Nova Scotia, is part of the transtensional basin fill that formed during dextral strike-slip motion between Avalonia and the Meguma terranes following the Acadian Orogeny. Paleomagnetic analysis of the Fountain Lake Group offers a paleolatitude estimate for the Laurentian accretionary margin in the Early Carboniferous as well as locality-specific paleomagnetic directions, which indicate clockwise-sense block rotations during dextral strike-slip motion along the Cobequid Fault zone. Stepwise demagnetization of 142 specimens from 20 sites in three Fountain Lake Group localities across the Cobequid Highlands (Squally Point, West Moose River, and Wentworth exposures) reveals remanence consisting of an easily removed component of probable recent origin, and more persistent components carried by magnetite and hematite, which in petrographic and electron beam analysis appear to be of primary igneous and volcanic oxidation origins, respectively. Sites from all three localities carry stable characteristic remanent magnetization (ChRM) directions that assume similar moderate downward inclinations when tilt-corrected. A Block Rotation Fisher analysis inclination-only fold test demonstrated best agreement at 90% unfolding, showing that remanence acquisition pre-dates Alleghenian deformation in the Late Carboniferous and is most likely of primary 355 Ma age. Paleomagnetic results for the Squally Point, West Moose River, and Wentworth localities show relative rotations between the blocks that are variously clockwise-rotated compared with a Laurentia cratonic reference frame. Inclinations at all three localities imply a subtropics paleolatitude for the margin (at Squally Point, 27.2° ± 9.4°; N = 7 sites), directly supporting the depicted location of Laurentia and its Appalachian accretionary margin in most Devonian to Early Carboniferous reconstructions.

Structure of phytoplankton functional groups in shallow lakes with different equilibrium states

Changes in equilibrium states in shallow lakes are associated with disturbances and resilience. The study evaluated the structure and composition of phytoplankton functional groups in two lakes, Lagoa do Paó (turbid waters) and Santa Lúcia (clear waters). Monthly collections of limnological variables and phytoplankton occurred between August 2014 and June 2015 in the pelagic region. The lakes shared five functional groups: K, S1 , X1 , W2 and P, formed by coccoid and filamentous cyanobacteria, coccoid chlorophytes and euglenophytes, and desmids, respectively. The canonical correspondence analysis evidenced a clear separation, highlighting the groups TD, N, W2 and S1 in Santa Lúcia and functional groups composed of potentially toxic cyanobacteria in Lagoa do Paó (SN, Lo), indicating that the submerged macrophyte coverage can act promoting the phosphorous stabilization in the sediment in Santa Lúcia, reducing its contribution to the water column and inhibiting the dominance of the mentioned species. Temperature, pH, phosphorus and light attenuation coefficient influenced the occurrence of H1 , SN, S1 , W2 , X1 , D, and Lo , in the Lagoa do Paó. The composition and structure of the functional groups responded in the two lakes with some functional groups associated with toxic cyanobacteria occurring exclusively in Lagoa do Paó, having also been observed the sharing of some functional groups.

Study on evolution of groundwater-lake system in typical prairie open-pit coal mine area.

Due to the drought climate and a large amount of groundwater drainage, there are widespread environmental geological problems in prairie open-pit coal mining areas, such as hydrological cycle imbalance, soil desertification and prairie degradation. This study takes the Hulunbeir Prairie Yimin Open-pit Coal Mine as the research object. Basing on the investigation of the groundwater-lake system in the mining area, data of hydrological, meteorological and remote sensing image, the mathematical model of groundwater level-lake area response mechanism in the mining area was constructed by using the principle of water balance. And the influence of mining area development on the lake area of Yimin basin had been predicted and analyzed. The results show that in the past 35years of coal mining, the number of lake groups in Yimin basin has changed from 5 before mining (1982) to 2 (2018), and the total area of lakes has reduced from 6.94km2 before mining to 1.43km2 with an area reduction rate of 79%. The prairie lake-groundwater coupling model was constructed based on the principle of water balance, and the goodness-of-fit reached more than 0.83 after testing. Based on the model, it's predicted that when the Yimin Coal Mine is closed (2045), the area of Chaidaminol lake will shrink to 1.37km2 under the condition of little fluctuation of climatic factors and stable mine development.

Investigating the morphological and genetic divergence of arctic char (Salvelinus alpinus) populations in lakes of arctic Alaska.

Polymorphism facilitates coexistence of divergent morphs (e.g., phenotypes) of the same species by minimizing intraspecific competition, especially when resources are limiting. Arctic char (Salvelinus sp.) are a Holarctic fish often forming morphologically, and sometimes genetically, divergent morphs. In this study, we assessed the morphological and genetic diversity and divergence of 263 individuals from seven populations of arctic char with varying length‐frequency distributions across two distinct groups of lakes in northern Alaska. Despite close geographic proximity, each lake group occurs on landscapes with different glacial ages and surface water connectivity, and thus was likely colonized by fishes at different times. Across lakes, a continuum of physical (e.g., lake area, maximum depth) and biological characteristics (e.g., primary productivity, fish density) exists, likely contributing to characteristics of present‐day char populations. Although some lakes exhibit bimodal size distributions, using model‐based clustering of morphometric traits corrected for allometry, we did not detect morphological differences within and across char populations. Genomic analyses using 15,934 SNPs obtained from genotyping by sequencing demonstrated differences among lake groups related to historical biogeography, but within lake groups and within individual lakes, genetic differentiation was not related to total body length. We used PERMANOVA to identify environmental and biological factors related to observed char size structure. Significant predictors included water transparency (i.e., a primary productivity proxy), char density (fish·ha‐1), and lake group. Larger char occurred in lakes with greater primary production and lower char densities, suggesting less intraspecific competition and resource limitation. Thus, char populations in more productive and connected lakes may prove more stable to environmental changes, relative to food‐limited and closed lakes, if lake productivity increases concomitantly. Our findings provide some of the first descriptions of genomic characteristics of char populations in arctic Alaska, and offer important consideration for the persistence of these populations for subsistence and conservation.

ÇEŞİTLİ SUCUL HİPERSALİN HABİTATLARDAKİ (TÜRKİYE) PROKARYOTİK TOPLULUKLARIN VE NANOHALOARKEAL SOYLARIN ÇEŞİTLİLİĞİNİN YÜKSEK-VERİMLİ DİZİLEME VE KLONLAMA KULLANILARAK DEĞERLENDİRİLMESİ

IIn this study, distribution of the prokaryotic groups in Tuz Lake, Ayvalık and Tuzlagözü solar salterns was investigated using 16S rRNA gene targeted approaches. The relative abundance of prokaryotic taxa in the samples was detected by using high-throughput sequencing. Operational taxonomic units (OTUs) associated with Haloquadratum were the most abundant in MiSeq reads. Nanohaloarchaeota-related OTUs were rare (<1%) in Ayvalık and Tuzlagözü solar salterns, and around 5% in Tuz Lake. Other OTUs frequently found and shared in the samples were associated with Halorubrum, Halonotius and Salinibacter genera. Nanohaloarchaeota lineages, whose phylotypes have been frequently detected in diverse hypersaline environments, were examined in more detail by 16S rRNA gene cloning using group-specific primer. Some of the highly represented nanohaloarchaeal phylotypes in the clone libraries showed low similarity to any sequence in the database, generating two distinct clades. One of the novel lineages was found to be prominent in the clone library constructed from Ayvalık sample. Phylotypes showing 95-97% sequence similarity to Ca. Nanopetramus were also highly represented in Ayvalık. Phylotypes frequent in the clone libraries of Tuz Lake and Tuzlagözü samples were associated with a novel lineage, as well as Ca. Nanosalina and its relatives.

Geothermal Assessment of Target Formations Using Recorded Temperature Measurements for the Alberta No. 1 Geothermal Project

The Alberta No. 1 project is a planned power and heat (direct use) geothermal project located within the County of Grande Prairie and Municipal District of Greenview. For the project to successfully produce power and heat on a commercial scale, temperatures of 120 °C are desirable. The produced fluids must also be from highly permeable formations from depths of less than 4500 m. Bottomhole temperature measurements and wireline logs from Alberta’s extensive oil and gas database were used to determine the depths to target formations and temperatures within these formations in the project area. The target formations include the dolomitized carbonate units of Devonian age from the Beaverhill Lake Group to the top of the Precambrian Basement. Permeable Devonian-aged sandstone units such as the Granite Wash Formation are also targets. Results suggest that elevation to the top of the Beaverhill Lake Group range from 3104 m to 4094 m and temperatures at the top of the formation range from 87 °C to 123 °C in the study area. Elevation to the top of the Precambrian Basement ranges from 3205 m to 4223 m and temperatures at the formation top range from 74 °C to 124 °C. Within the area where Alberta No. 1 plans to drill, temperatures close to and exceeding 120 °C are expected within the target formations.

Bottom-up and top-down effects on phytoplankton functional groups in Hulun Lake, China

The debates about the extent to which phytoplankton in freshwater ecosystems are regulated by top-down or bottom-up forces have been ongoing for decades. This study examines the effects of bottom-up and top-down factors on the phytoplankton functional groups in a eutrophic lake. Phytoplankton and zooplankton were sampled and physical-chemical variables measured from May 2019 to October 2019 in Lake Hulun, China. Approximately 43 phytoplankton species were observed and grouped into 23 functional groups. For the zooplankton, about 27 species were observed and classified into 8 functional groups. The study revealed that the bottom-up effects of physical-chemical variables on some phytoplankton functional groups was stronger than the top-down effects of zooplankton. Water temperature (WT), total phosphorus (TP), total nitrogen (TN), conductivity (Cond), water transparency (SD), and dissolved oxygen (DO) significant influence the biomass of the phytoplankton functional groups. The biomass of phytoplankton functional groups was influenced positively by nutrient availability likely because nutrients influence the growth and reproduction of phytoplankton in freshwater. WT and DO had a positive influence on biomass of phytoplankton functional groups. Conversely, phytoplankton biomass revealed a decreasing trend when SD and Cond significantly increased. This study showed that zooplankton functional groups were positively correlated with phytoplankton biomass implying that the top-down control of phytoplankton by the zooplankton in the lake is not strong enough to produce a negative effect. It is evident that the zooplankton functional groups in Lake Hulun are controlled more by bottom-up force than top-down.