The depositional history of the Bonneville Salt Flats, a perennial saline pan in Utah's Bonneville basin, has poor temporal constraints, and the climatic and geomorphic conditions that led to saline pan formation there are poorly understood. We explore the late Pleistocene to Holocene depositional record of Bonneville Salt Flats cores. Our data challenge the assumption that the saline pan formed from the desiccation of Lake Bonneville, the largest late Pleistocene lake in the Great Basin, which covered this area from 30 to 13 cal ka BP. We test two hypotheses: whether climatic transitions from (1) wet to arid or (2) arid to wet led to saline pan deposition. We describe the depositional record with radiocarbon dating, sedimentological structures, mineralogy, diatom, ostracode, and portable X-ray fluorescence spectrometer measurements. Gypsum and carbonate strontium isotope ratio measurements reflect changes in water sources. Three shallow saline lake to desiccation cycles occurred from >45 and >28 cal ka BP. Deflation removed Lake Bonneville sediments between 13 and 8.3 cal ka BP. Gypsum deposition spanned 8.3 to 5.4 cal ka BP, while the oldest halite interval formed from 5.4 to 3.5 cal ka BP during a wetter period. These findings offer valuable insights for sedimentologists, archaeologists, geomorphologists, and land managers.

Fildes Peninsula, on King George Island, has been greatly influenced by recent rapid climate warming. Lakes are pervasive features of Fildes Peninsula landscapes, some of which are used as water sources for Antarctic stations. We studied seven Fildes Peninsula lakes to explore differences among lakes and between seasons in phytoplankton and bacterioplankton communities. We measured environmental variables, analysed pigments using high-performance liquid chromatography and examined bacterial DNA through high-throughput sequencing of the 16S rRNA gene. The main driver structuring microbial communities was the season (i.e. spring vs autumn). Chlorophyceae were the dominant phytoplankton group in all lakes and both seasons. Indicator bacteria for each season were identified, including Flavobacterium, Polaromonas and Oxalobacteraceae as indicators of spring conditions under thick ice, whereas Frankiales and Verrucomicrobia were indicator species of autumn following the ice-free summer. The indicator species for spring are generally observed in oligotrophic conditions, whereas many of the autumn indicators are commonly found in soils. There were lesser between-lake differences in microbial communities in autumn, at the end of the open-water period, than in spring at the end of the ice-covered period. This study will act as the basis for future assessments of changes in aquatic microbial communities.

Protection of Antarctica's biodiversity and ecosystem values is enshrined in the Protocol on Environmental Protection to the Antarctic Treaty, which provides for the designation of Antarctic Specially Protected Areas (ASPAs) to areas with outstanding values. Concern has been raised that existing ASPAs fail to prioritize areas to maximize the likelihood of ensuring the long-term conservation of Antarctic ecosystems and biodiversity. The absence of systematic and representative protection is particularly acute for inland aquatic ecosystems, which support a disproportionate amount of inland biodiversity. This paper promotes the case for overt inclusion of inland waters as a critical component of a representative protected area framework for Antarctica, thereby addressing their current underrepresentation. We set out a structured approach to enable the selection of representative freshwater systems for inclusion in the ASPA framework that, with modification, could also be applied across other Antarctic habitats. We acknowledge an overall lack of information on the biogeography of inland aquatic diversity and recommend increased use of remote data collection along with classification tools to mitigate this, as well as the need for the consideration of catchment-scale processes. Changes that accompany contemporary and anticipated climate change make the need for the conservation of representative biodiversity increasingly urgent.

Paleoperspectives of climate provide important information for understanding future climate, particularly in arid regions such as California, where water availability is uncertain from year to year. Here, we present a record from Barley Lake, California, focusing on the interval spanning the Younger Dryas (YD) to the early Holocene (EH), a period of acute and rapid global climate change. Twelve radiocarbon dates constrain the timing between 12.9 and 8.1 ka. We combine a variety of sediment analyses to infer changes in lake productivity, relative lake level, and runoff dynamics. In general, the lake is characterized by two states separated by a <200-year transition: (1) a variably deep, lower-productivity YD lake; and (2) a two-part variably shallow, higher-productivity EH lake. Inferred EH winter-precipitation runoff reveals dynamic multidecadal-to-centennial-scale variability, in agreement with the EH lake-level data. The Barley Lake archive captures both hemispheric and regional signals of climate change across the transition, suggesting a role for both ocean-atmosphere and insolation forcing. Our paleoperspective emphasizes California's sensitivity to climate change and how that change can generate abrupt shifts in limnological regimes.

Lacustrine sedimentary records and the proxies contained within them are valuable archives of past climate. However, the resolution of these records is frequently coarse or contains a high degree of uncertainty, making it difficult to resolve how climatic variability impacts the ecosystems on which humans depend. The goal of this study is to couple recent sediment cores sampled at centimeter-scale resolution with paleo- and historical information about lake levels to document how changes in the paleoenvironment impact the paleoecology of a rift basin lake. We present multiproxy data from three short cores collected from Ferguson's Gulf (FG), a shallow embayment connected to the western shore of Lake Turkana, Kenya. Five distinct biozones were interpreted on the basis of ostracods and geochemistry (δ18O, δ13C, and major elements), spanning the Little Ice Age (LIA) to the modern. Overall, ostracod total abundance and assemblage diversity decreased up-core, with the largest total abundance and genera diversity occurring during the LIA. This fits with regional datasets that indicate the Eastern Branch of the East African Rift System was wetter during the LIA than it is today. This also suggests that human impact in and around Lake Turkana has weakened the resiliency of the ecosystems in FG.

A quantitative high-resolution autumn (September–November) temperature reconstruction for the southeastern Swiss Alps back to AD 1580 is presented here. We used the annually resolved biogenic silica (diatoms) flux derived from the accurately dated and annually sampled sediments of Lake Silvaplana (46°27′N, 9°48′E, 1800 m a.s.l.). The biogenic silica flux smoothed by means of a 9-yr running mean was calibrated (r=0.70, p<0.01) against local instrumental temperature data (AD 1864–1949). The resulting reconstruction (± 2 standard errors=±0.7 °C) indicates that autumns during the late Little Ice Age were generally cooler than they were during the 20th century. During the cold anomaly around AD 1600 and during the Maunder Minimum, however, the reconstructed autumn temperatures did not experience strong negative departures from the 20th-century mean. The warmest autumns prior to 1900 occurred around AD 1770 and 1820 (0.75 °C above the 20th-century mean). Our data agree closely with two other autumn temperature reconstructions for the Alps and for Europe that are based on documentary evidence and are completely unrelated to our data, revealing a very consistent picture over the centuries.

Sediment magnetic properties of a short core from Sharkey Lake, MN, record the effects of Euroamerican settlement and climate change over the last 150 yr. The onset of European-style farming led to increased erosion, reflected in high values of concentration-dependent parameters such as magnetic susceptibility (ĸ), Isothermal Remanent Magnetization (IRM), and Anhysteretic Remanent Magnetization (ARM). These high values are only partially due to increased supply of terrigenous material to the lake, and recent sediment contains an additional component of authigenic fine (single-domain) magnetite, most likely magnetosomes from magnetotactic bacteria. High organic productivity in the lake during the 1920s to 1940s drought increased this authigenic component resulting in highly magnetic fine-grained sediment. A comparison with older Holocene sediment from the same lake shows that, over time, most of the fine magnetic signal is lost after deposition, leading to decreases in magnetization and a bimodal grain size distribution of ultrafine, superparamagnetic grains and coarser multidomain particles, evident from measurements of ARM/IRM ratios, hysteresis measurements, and low-temperature analyses. The effects of dissolution and the superposition of climate and land-use signals complicate the use of recent sediments as modern analogs for sediment magnetic analyses.

Byers Peninsula, Livingston Island, was one of the first sites in Antarctica designated for environmental conservation and scientific protection. Research on Byers Peninsula has been predominantly international, with 88 indexed publications (93% of them published during last 20 years) from 209 authors affiliated to 110 institutions from 22 nations, all of which are signatories to the Antarctic Treaty. Palaeontological research represented 20% of the published articles. The variety of freshwater bodies within the area has made Byers Peninsula a reference site for limnological studies (24% of papers). The site also contains numerous outcrops and periglacial features relevant to geology, stratigraphy and geomorphology (29%). Terrestrial biodiversity is extraordinarily high for lichens, bryophytes and invertebrates (15% of articles). Only 5% of the publications concern research on human activities, including both archaeology and impact monitoring. Glaciology, meteorology and climatology studies represent only 7% of papers. This work highlights the international and multidisciplinary nature of science conducted on Byers Peninsula in order to promote international cooperation and to provide information relevant for environmental management and conservation.

A survey of the 1:100,000 topographic maps of Papua New Guinea revealed that there are about 5383 freshwater lakes in the country. They range in size up to 647 km2 but the majority are less than 10 ha. They are found at all altitudes to over 4000 m but most are situated below 40 m in the floodplains of the Fly, Sepik and Aramia rivers. The majority of lakes are undoubtedly shallow but depths range up to 360 m. The lakes were formed in at least 20 different ways but the majority by fluviatile action. The few data on chemical and physical conditions suggest that most lakes are chemically poor with low light penetration and low pH values. With the possible exception of the macrophytes the fauna and flora of the lakes are virtually unstudied, particuarly from a quantitative aspect. Most lakes are probably polymictic.

This study is the first published survey of diatom-environment relationships on sub-Antarctic Macquarie Island. Fifty-eight sites in 50 coastal and inland lakes were sampled for benthic diatoms and water chemistry. 208 diatom species from 34 genera were identified. Multivariate analyses indicated that the lakes were distributed along nutrient and conductivity gradients. Conductivity, pH, phosphate (SRP), silicate and temperature all explained independent portions of the variance in the diatom data. Transfer functions provide a quantitative basis for palaeolimnological studies of past climate change and human impacts, and can be used to establish baseline conditions for assessing the impacts of recent climate change and the introduction of non-native plants and animals. Statistically robust diatom transfer functions for conductivity, phosphate and silicate were developed, while pH and temperature transfer functions performed less well. The lower predictive abilities of the pH and temperature transfer functions probably reflect the broad pH tolerance range of diatoms on Macquarie Island and uneven distribution of lakes along the temperature gradient. This study contributes to understanding the current ecological distribution of Macquarie Island diatoms and provides transfer functions that will be applied in studies of diatoms in lake sediment cores to quantitatively reconstruct past environmental changes.

Lake Wilson, a perennially ice-capped, deep (>100 m) lake at 80°S in southern Victoria Land was investigated in January 1993. Water chemistry and physical structure showed three distinct layers; an upper c. 35 m mixed layer of low salinity, moderately turbid water; a less turbid mid layer, 20 m thick of slightly higher salinity and supersaturated with oxygen; and a deep 20 m brackish layer (conductivity c. 4000 μS cm−1) with anoxic conditions in the lower 5 m. Extreme supersaturation of N2O (up to 400 times air saturation) together with high nitrate concentration (4000 mg m−3) was recorded in the deep layer. Phytoplankton biomass and photosynthetic activity was confined to the upper mixed layer and the band of supersaturated dissolved oxygen located at 40–55 m appears to represent a relict layer from when the lake level was lower. The evidence from a comparison of profiles between 1975 and 1993 suggests that Lake Wilson has risen 25 m since 1975, synchronous with a period of lake level rise in the McMurdo Dry Valleys lakes to the north at 77°S. Geochemical diffusion models indicate that Lake Wilson had evaporated to a smaller brine lake about 1000 yrs BP, which also fits the pattern shown by the McMurdo Dry Valleys lakes. Climate changes influencing lake levels have thus covered a wide area of southern Victoria Land.

Lake Untersee is the largest freshwater lake in the interior of East Antarctica. It is a perennially ice-covered, max. 169 m deep, ultra-oligotrophic lake. In contrast to earlier studies, we found clear evidence for physical and chemical stratification in the summer of 1991–92. However, the stratification was restricted to a trough, c. 500 m wide and up to 105 m deep, in the south-western part of the lake. There, the water body was distinctly stratified as indicated by sharp vertical gradients of temperature, pH, dissolved oxygen, and electrical conductivity. The water column was anoxic below 80 m. The chemical stratification is also indicated by changes of ionic ratios. Moreover, there was some evidence for methanogenesis and bacterial sulphate reduction in Lake Untersee.

Two sediment cores taken from Jaw lake (Bunger Hills, East Antarctica) were analysed for diatom composition and abundance. A diatom-salinity transfer function developed for the nearby Vestfold Hills was used to determine palaeosalinity reconstructions from the assemblages preserved in each of the cores. There is a large step-wise decrease in salinity in the second core from at least c. 4000 to c. 2000 uncorrected 14C yr BP. The salinity record from the first core starts at c. 3000 uncorrected 14C yr BP and is comparable with the salinity of the second core between c. 3000 and c. 2000 uncorrected 14C yr BP. Sudden lake water dilution in both cores at c. 1900 uncorrected 14C yr BP is followed by brief increases in lake water salinity between c. 1900 and c. 500 uncorrected 14C yr BP, after which gradual dilution to present occurs. This analysis of the local environmental history of this saline lake reveals a mid–late Holocene evolution of the lake basin similar to that documented from earlier marine and freshwater lacustrine sediments in the Bunger Hills. The high coherence of the independent sediment records suggests a robust general palaeosalinity reconstruction of the lake is achieved in addition to providing evidence for the fidelity of single sediment cores as useful and adequate representation of the palaeolimnological histories of Antarctic lakes.

Le peuplement en Hydracariens (Hydrachnellae, Acari) a été étudié dans 108 stations (86 espèces) des Pyrénées centrales. L'analyse canonique et l'analyse factorielle des correspondances permettent de mettre en évidence : - d'une part, une corrélation entre les facteurs écologiques habituellement reconnus (température, vitesse du courant,...) et un certain nombre de paramètres topographiques, hydrologiques, géologiques,..., qui constituent un complexe stationnel, stable dans le temps pour une même station. - d'autre part, une corrélation entre les complexes stationnels et un certain nombre (8) d'associations d'Hydracariens. Cinq paramètres, - altitude de la source, altitude de la station, pente, surface du bassin-versant et régime des eaux, - suffisent à définir un complexe stationnel et à expliquer, avec la nature du substrat (galets ou mousses), la distribution des espèces. Le régime des eaux, notamment, joue un rôle fondamental dans cette distribution et justifie la distinction des auteurs de langue allemande entre faune de Mittel - et Hochgebirge. En fonction du substrat, du taux de reproduction, du cycle biologique, différents types biologiques d'Hydracariens sont mis en évidence. Mais, pour expliquer la structure des communautés, et notamment leur diversité, il faut faire appel à des notions comme la stabilité du biotope (durée), sa surface (espace), la distance entre biotopes équivalents, - c'est-à-dire à la théorie des îles de Mac-Arthur et Wilson. Le peuplement des biotopes instables, de surface limitée et isolés est à la limite aléatoire.

Un bilan d'entrées-sorties du phosphore total pour le Léman entre 1964 et 1983 est présenté. Dans l'ensemble, le lacréalise l'élimination nette de Ptot à un taux moyen de 0,2 an-1, mais avec de fortes fluctuations, les années à sédimentation nette alternant avec celles à régénération nette. Les conditions météorologiques jouent un rôle capital dans cette alternance.L'application au Léman du modèle simple de Vollenweider et des normes OCDE est discutée. L'approximation du coefficient d'élimination Φ à l'aide du coefficient de renouvellement de l'eau conduit à une forte surestimation de l'élimination.Pour tenir compte de la variabilité de Φ, l'on simule l'évolution du stock selon divers scénarios en suivant une approche stochastique. Il s'avère qu'une variabilité réaliste de Φ (50 %) peut provoquer des fluctuations interannuelles du stock de plusieurs milliers de tonnes.Dans les conditions de charge actuelle (1200 t an- 1), ou même après une réduction de 400 t an- 1 suite à une interdiction des phosphates dans les détergents, le lac ne pourra pas atteindre l'objectif d'un stock à 2 000-3 000 t.