Saline systems of the Great Plains of western Canada: an overview of the limnogeology and paleolimnology

In much of the northern Great Plains, saline and hypersaline lacustrine brines are the only surface waters present. As a group, the lakes of this region are unique: there is no other area in the world that can match the concentration and diversity of saline lake environments exhibited in the prairie region of Canada and northern United States. The immense number of individual salt lakes and saline wetlands in this region of North America is staggering. Estimates vary from about one million to greater than 10 million, with densities in some areas being as high as 120 lakes/km(2). Despite over a century of scientific investigation of these salt lakes, we have only in the last twenty years advanced far enough to appreciate the wide spectrum of lake types, water chemistries, and limnological processes that are operating in the modern settings. Hydrochemical data are available for about 800 of the lake brines in the region. Composition, textural, and geochemical information on the modern bottom sediments has been collected for just over 150 of these lakes. Characterization of the biological and ecological features of these lakes is based on even fewer investigations, and the stratigraphic records of only twenty basins have been examined. The lake waters show a considerable range in ionic composition and concentration. Early investigators, concentrating on the most saline brines, emphasized a strong predominance of Na(+ )and SO(4)(-2 )in the lakes. It is now realized, however, that not only is there a complete spectrum of salinities from less than 1 ppt TDS to nearly 400 ppt, but also virtually every water chemistry type is represented in lakes of the region. With such a vast array of compositions, it is difficult to generalize. Nonetheless, the paucity of Cl-rich lakes makes the northern Great Plains basins somewhat unusual compared with salt lakes in many other areas of the world (e.g., Australia, western United States). Compilations of the lake water chemistries show distinct spatial trends and regional variations controlled by groundwater input, climate, and geomorphology. Short-term temporal variations in the brine composition, which can have significant effects on the composition of the modern sediments, have also been well documented in several individual basins. From a sedimentological and mineralogical perspective, the wide range of water chemistries exhibited by the lakes leads to an unusually large diversity of modern sediment composition. Over 40 species of endogenic precipitates and authigenic minerals have been identified in the lacustrine sediments. The most common non-detrital components of the modern sediments include: calcium and calcium-magnesium carbonates (magnesian calcite, aragonite, dolomite), and sodium, magnesium, and sodium-magnesium sulfates (mirabilite, thenardite, bloedite, epsomite). Many of the basins whose brines have very high Mg/Ca ratios also have hydromagnesite, magnesite, and nesquehonite. Unlike salt lakes in many other areas of the world, halite, gypsum, and calcite are relatively rare endogenic precipitates in the Great Plains lakes. The detrital fraction of the lacustrine sediments is normally dominated by clay minerals, carbonate minerals, quartz, and feldspars. Sediment accumulation in these salt lakes is controlled and modified by a wide variety of physical, chemical, and biological processes. Although the details of these modern sedimentary processes can be exceedingly complex and difficult to discuss in isolation, in broad terms, the processes operating in the salt lakes of the Great Plains are ultimately controlled by three basic factors or conditions of the basin: (a) basin morphology; (b) basin hydrology; and (c) water salinity and composition. Combinations of these parameters interact to control nearly all aspects of modern sedimentation in these salt lakes and give rise to four 'end member' types of modern saline lacustrine settings in the Great Plains: (a) clastics-dominated playas; (b) salt-dominated playas; (c) deep water, non-stratified lakes; and (d) deep water, "permanently" stratified lakes

Paleohydrology, Sedimentology, and Geochemistry of Two Meromictic Saline Lakes in Southern Saskatchewan

The Northern Great Plains of western Canada contain numerous saline and hypersaline lakes. Most of these lakes are shallow (< 3 m) and exhibit playa characteristics. Some, however, are relatively deep, permanent water bodies. The sediment records of these deep perennial saline lakes offer an excellent opportunity to evaluate key paleohydrologic and hydrochemical parameters. Variations in these parameters may, in turn, be interpreted with respect to climatic fluctuations in the region. Waldsea and Deadmoose lakes, located in south-central Saskatchewan, are both presently meromictic, with saline Mg-Na-SO4-CI waters overlying denser hypersaline brines of similar composition. The modern sediments of the lakes consist of a mixture of organic matter, finegrained detrital elastics (mainly clay minerals, carbonate minerals, quartz, and feldspars), and finely crystalline endogenic/authigenic precipitates (aragonite, gypsum, calcite, pyrite, and mirabilite). Variations in mineralogy and chemistry of sediment cores from the morphologically simple Waldsea basin show that the lake was much shallower and more saline about 4000 years ago. Although water levels have since generally increased in the basin giving rise to higher organic productivity and greater inorganic carbonate precipitation, there is also evidence of several hydrologie reversals during the last 2000 years. The stratigraphy preserved in nearby Deadmoose Lake is much more complex because of the irregular basin morphology. Lower water levels about 1000 years ago created several isolated but still relatively deep lakes in the Deadmoose basin.Les grandes plaines du nord de l'ouest du Canada contiennent de nombreux lacs salés et hypersalés. La plupart de ces lacs sont peu profonds (< 3 m) et offrent les caractéristiques des playas. D'autres, par contre, sont des plans d'eau permanents relativement profonds. Les données sédimentologiques de ces derniers permettent d'évaluer certains paramètres clés de paléohydrologie et d'hydrochimie. Les variations qu'offrent ces paramètres peuvent à leur tour être interprétées en fonction des fluctuations climatiques qu'a connues la région. Les lacs Waldsea et Deadmoose, dans le centre-sud de la Saskatchewan, sont méromictiques et leurs eaux composées de Mg-Na-So4-Cl recouvrent une saumure hypersaline plus dense, mais de composition semblable. Les sédiments actuels de ces lacs consistent en un mélange de matière organique, de roches détritiques à grains fins (surtout des minéraux argileux et carbonates ainsi que des quartz et des feldspaths) et de calcaires de précipitation cristallins à grains fins endogènes et authigènes (aragonite, gypse, calcite, pyrite et mirabilite). La minéralogie et la chimie des sédiments contenus dans les carottes recueillies dans le bassin du lac Waldsea, de morphologie simple, montrent des variations qui indiquent que le lac était beaucoup moins profond et plus salé il y a 4000 ans. Bien que, de façon générale, les niveaux lacustres se soient haussés depuis, ce qui a donné lieu à une production accrue de matière organique et à une plus forte précipitation des carbonates inorganiques, on trouve les témoins de plusieurs inversions de nature hydrologique depuis les 2000 dernières années. Non loin, au lac Deadmoose, la stratigraphie est beaucoup plus complexe en raison de la morphologie irrégulière du bassin. Il y a 1000 ans environ, les bas niveaux lacustres ont été à l'origine de la formation de plusieurs lacs isolés et relativement profonds dans le bassin Deadmoose.den nôrdlichen groBen Ebenen von West-Kanada gibt es zahlreiche salzhaltige und hypersalzhaltige Seen. Die meisten dieser Seen sind seicht (< 3 m) und zeigen Pfannen Charakteristika. Einige hingegen sind relativ tiefe permanente Wasserspiegel. Die Sediment-Belege dieser tiefen, bestândigen Salz-Seen bieten eine ausgezeichnete Gelegenheit, die paleohydrologischen und hydrochemischen Schlùssel-Parameter zu bewerten. Variationen dieser Parameter kônnen ihrerseits interpretiert werden in Bezug auf die klimatischen Fluktuationen in dieser Region. Die Seen Waldsea und Deadmoose, die im sùdlichen Zentrum von Saskatchewan liegen, sind gegenwârtig beide meromiktisch, mit salinen Mg-Na-SO4-Cl Wassern, welche dichtere, hypersaline Salzlaken âhnlicher Zusammensetzung ùberlagern. Die gegenwàrtigen Sedimente dieser Seen bestehen aus einer Mischung von organischem Material, feinkôrnigen Trùmmergesteinen (hauptsàchlich Lehm-Minerale, Karbonat-Minerale, Quartz und Feldspate), und fein kristallinen endogenen/ authigenen Niederschlàgen (Aragonit, Gipsstein, Kalkspat, Pyrit und Mirabilit). Variationen in der Minéralogie und Chemie der Sediment-Keme von dem morphologisch einfachen Waldsea-Becken zeigen, dafî der See vor etwa 4000 Jahren viel seichter und saliner war. Obwohl die Wasserspiegel seitdem im Allgemeinen in dem Becken angestiegen sind, was zu hôherer organischer Produktivitàt und vestârktem inorganischem Karbonat-Niederschlag fùhrte, findet man auch Belege fur einige hydrologische Umschwùnge wâhrend der letzten 2000 Jahre. Die im nahegelegenen Deadmoose-See erhaltene Stratigraphie ist viel komplexer auf Grund der unregelmàfîigen Morphologie des Beckens. Niedrigere Wasserspiegel vor ungefâhr 1000 Jahren fùhrten zu einigen isolierten, aber immer noch relativ tiefen Seen im Deadmoose-Becken

A gap analysis on modelling of sea lice infection pressure from salmonid farms. I. A structured knowledge review

Sustainability of aquaculture, an important component of the blue economy, relies in part on ensuring assessment of environmental impact and interactions relating to sea lice dispersing from open pen salmon and trout farms. We review research underpinning the key stages in the sea lice infection process to support modelling of lice on wild salmon in relation to those on farms. The review is split into 5 stages: larval production; larval transport and survival; exposure and infestation of new hosts; development and survival of the attached stages; and impact on host populations. This modular structure allows the existing published data to be reviewed and assessed to identify data gaps in modelling sea lice impacts in a systematic way. Model parameterisation and parameter variation is discussed for each stage, providing an overview of knowledge strength and gaps. We conclude that a combination of literature review, empirical data collection and modelling studies are required on an iterative basis to ensure best practice is applied for sustainable aquaculture. The knowledge gained can then be optimised and applied at regional scales, with the most suitable modelling frameworks applied for the system, given regional limitations

A gap analysis on modelling of sea lice infection pressure from salmonid farms. II. Identifying and ranking knowledge gaps: output of an international workshop

Sea lice are a major health hazard for farmed Atlantic salmon in Europe, and their impact is felt globally. Given the breadth of ongoing research in sea lice dispersal and population modelling, and focus on research-led adaptive management, we brought experts together to discuss research knowledge gaps. Gaps for salmon lice infection pressure from fish farms were identified and scored by experts in sea lice-aquaculture-environment interactions, at an international workshop in 2021. The contributors included experts based in Scotland, Norway, Ireland, Iceland, Canada, the Faroe Islands, England and Australia, employed by governments, industry, universities and non-government organisations. The workshop focused on knowledge gaps underpinning 5 key stages in salmon lice infection pressure from fish farms: larval production; larval transport and survival; exposure and infestation of new hosts; development and survival of the attached stages; and impact on host populations. A total of 47 research gaps were identified; 5 broad themes emerged with 13 priority research gaps highlighted as important across multiple sectors. The highest-ranking gap called for higher quality and frequency of on-farm lice count data, along with better sharing of information across sectors. We highlight the need for synergistic international collaboration to maximise transferable knowledge. Round table discussions through collaborative workshops provide an important forum for experts to discuss and agree research priorities

The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis ... The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model ... Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic