Summary
Peñahueca is an athalassohaline hypersaline inland ephemeral lake originated under semiarid conditions in the central Iberian Peninsula (Spain). Its chemical composition makes it extreme for ...microbial life as well as a terrestrial analogue of other planetary environments. To investigate the persistence of microbial life associated with sulfate‐rich crusts, we applied cultivation‐independent methods (optical and electron microscopy, 16S rRNA gene profiling and metagenomics) to describe the prokaryotic community and its associated viruses. The diversity for Bacteria was very low and was vastly dominated by endospore formers related to Pontibacillus marinus of the Firmicutes phylum. The archaeal assemblage was more diverse and included taxa related to those normally found in hypersaline environments. Several ‘metagenome assembled genomes’ were recovered, corresponding to new species of Pontibacillus, several species from the Halobacteria and one new member of the Nanohaloarchaeota. The viral assemblage, although composed of the morphotypes typical of high salt systems, showed little similarity to previously isolated/reconstructed halophages. Several putative prophages of Pontibacillus and haloarchaeal hosts were identified. Remarkably, the Peñahueca sulfate‐rich metagenome contained CRISPR‐associated proteins and repetitions which were over 10‐fold higher than in most hypersaline systems analysed so far.
Sulfur controls the fate of many geochemical elements in lake sediments, including iron, phosphorus and environmentally important trace elements. We measured the speciation of pore-water and ...sediment-bound sulfur (aqueous sulfate and sulfides, elemental sulfur, iron monosulfide, pyrite, organic sulfur) and supporting geochemical variables (carbon, oxygen, iron) in the sediments of a perennially oxygenated and a seasonally anoxic basin of an oligotrophic lake in Québec, using a combination of pore-water analyses, sequential extractions and X-ray absorption near edge structure. A non-steady state early diagenetic model was developed and calibrated against this extensive dataset to help unravel the pathways and quantify the rates of S transformations. Results suggest that the main source of S to the sediments is the settling of organic ester-sulfate (R-O-SO3-H). Hydrolysis of these compounds provides an additional source of sulfate for anaerobic microbial oxidation of sedimentary organic matter, releasing sulfide to the pore-water. Reduced solid-bound S species accumulate as thiols (R-SH) and iron sulfides in the perennially oxygenated and seasonally anoxic basin, respectively. The model-estimated rate constant for R-SH formation is lower than previously estimated for this particular lacustrine site, but similar to that proposed for marine shelf sediments. The solid sediment S profiles, however, carry the imprint of the time-dependent sulfate input to the lake. Iron sulfide enrichments formed during past decades of elevated atmospheric SO4 deposition are presently dissolving. In the sediments of the perennially oxygenated basin this reaction hampers the build-up of Fe(III) (oxy)hydroxide near the sediment–water interface.
Holocene climate in the high tropical Andes was characterized by both gradual and abrupt changes, which disrupted the hydrological cycle and impacted landscapes and societies. High-resolution ...paleoenvironmental records are essential to contextualize archaeological data and to evaluate the sociopolitical response of ancient societies to environmental variability. Middle-to-Late Holocene water levels in Lake Titicaca were reevaluated through a transfer function model based on measurements of organic carbon stable isotopes, combined with high-resolution profiles of other geochemical variables and paleoshoreline indicators. Our reconstruction indicates that following a prolonged low stand during the Middle Holocene (4000 to 2400 BCE), lake level rose rapidly ~15 m by 1800 BCE, and then increased another 3 to 6 m in a series of steps, attaining the highest values after ~1600 CE. The largest lake-level increases coincided with major sociopolitical changes reported by archaeologists. In particular, at the end of the Formative Period (500 CE), a major lake-level rise inundated large shoreline areas and forced populations to migrate to higher elevation, likely contributing to the emergence of the Tiwanaku culture.
China is confronting the challenge of accelerated lake eutrophication, where Lake Dianchi is considered as the most serious one. Eutrophication control for Lake Dianchi began in the mid-1980s. ...However, decision makers have been puzzled by the lack of visible water quality response to past efforts given the tremendous investment. Therefore, decision makers desperately need a scientifically sound way to quantitatively evaluate the response of lake water quality to proposed management measures and engineering works. We used a water quality modeling based scenario analysis approach to quantitatively evaluate the eutrophication responses of Lake Dianchi to an under-construction water diversion project. The primary analytic framework was built on a three-dimensional hydrodynamic, nutrient fate and transport, as well as algae dynamics model, which has previously been calibrated and validated using historical data. We designed 16 scenarios to analyze the water quality effects of three driving forces, including watershed nutrient loading, variations in diverted inflow water, and lake water level. A two-step statistical analysis consisting of an orthogonal test analysis and linear regression was then conducted to distinguish the contributions of various driving forces to lake water quality. The analysis results show that (a) the different ways of managing the diversion projects would result in different water quality response in Lake Dianchi, though the differences do not appear to be significant; (b) the maximum reduction in annual average and peak Chl-a concentration from the various ways of diversion project operation are respectively 11% and 5%; (c) a combined 66% watershed load reduction and water diversion can eliminate the lake hypoxia volume percentage from the existing 6.82% to 3.00%; and (d) the water diversion will decrease the occurrence of algal blooms, and the effect of algae reduction can be enhanced if diverted water are seasonally allocated such that wet season has more flows.
Display omitted
•A model-based scenario analysis for quantitative evaluation of lake responses.•A two-step statistical analysis to distinguish the effects on eutrophication.•Water diversion will decrease the occurrence of algal blooms in Lake Dianchi.•Watershed nutrient loading has the greatest effect on lake water quality.
During the re‐eutrophication of Lake Erie, dissolved reactive phosphorus (DRP) loading and concentrations to the lake have nearly doubled, while particulate phosphorus (PP) has remained relatively ...constant. One potential cause of increased DRP concentrations is P stratification, or the buildup of soil‐test P (STP) in the upper soil layer (<5 cm). Stratification often accompanies no‐till and mulch‐till practices that reduce erosion and PP loading, practices that have been widely implemented throughout the Lake Erie Basin. To evaluate the extent of P stratification in the Sandusky Watershed, certified crop advisors were enlisted to collect stratified soil samples (0–5 or 0–2.5 cm) alongside their normal agronomic samples (0–20 cm) (n = 1758 fields). The mean STP level in the upper 2.5 cm was 55% higher than the mean of agronomic samples used for fertilizer recommendations. The amounts of stratification were highly variable and did not correlate with agronomic STPs (Spearman's r = 0.039, p = 0.178). Agronomic STP in 70% of the fields was within the buildup or maintenance ranges for corn (Zea mays L.) and soybeans Glycine max (L.) Merr. (0–46 mg kg−1 Mehlich‐3 P). The cumulative risks for DRP runoff from the large number of fields in the buildup and maintenance ranges exceeded the risks from fields above those ranges. Reducing stratification by a one‐time soil inversion has the potential for larger and quicker reductions in DRP runoff risk than practices related to drawing down agronomic STP levels. Periodic soil inversion and mixing, targeted by stratified STP data, should be considered a viable practice to reduce DRP loading to Lake Erie.
Core Ideas
P stratification increases surficial soil‐test levels by 55% over agronomic cores.
Agronomic soil‐test levels are not good indicators of surficial soil‐test levels.
Soils in maintenance range account for the largest proportion of DRP runoff risks.
Targeted stratification reduction could reduce DRP runoff more than drawdown.
Stratification reduction could reduce DRP runoff more quickly than drawdown.
•The quality of remotely sensed reflectance products was assessed.•A robust power function model was constructed for inland lakes.•The consistency of the SDD values from Landsat series data was ...evaluated.
Water clarity (expressed as Secchi disk depth (SDD)) reflects light transmission capacity of a water body and influences growth of aquatic plants, aquatic organisms, and primary productivity. Here, we calibrated and validated a general model based on Landsat series data for deriving SDD of various inland waters across China. The quality of remotely sensed reflectance products from different Landsat series images was assessed using in situ reflectance measurements. The results indicated that the products in the visible bands are the most robust and stable to estimate SDD for inland waters. Subsequently, a simple power function model based on red band was built using 887 pairs of in situ SDD measurements and concurrent Landsat images. The model was validated with an independent dataset of 246 SDD measurements, and the results showed that the mean relative error and normalized root mean square error were 34.2% and 55.4%, respectively. Finally, the model was applied to Landsat images acquired between 2016 and 2018 to investigate the SDD spatial distribution of all lakes with water area ≥ 10 km2 (total 641 lakes) in China. The estimation results demonstrated that the Eastern Plain Lake Zone and Northeast Plain Lake zone have relatively low SDD, with multiyear average SDD of 0.56±0.17 m and 0.47±0.29 m, respectively. The Yunnan‐Guizhou Plateau Lake Zone and Tibetan Plateau Lake Zone have relatively high SDD, with multiyear average SDD of 1.48 ± 0.86 m and 1.30 ± 0.83 m, respectively. The results indicated that the proposed model exhibits strong ability to accurately construct SDD coverage for various lakes.
Display omitted
There is a growing interest for the use of coliphage as an alternative indicator to assess fecal pollution in recreational waters. Coliphage are a group of viruses that infect Escherichia coli and ...are considered as potential surrogates to infer the likely presence of enteric viral pathogens. We report the use of a dead-end hollow fiber ultrafiltration single agar layer method to enumerate F+ and somatic coliphage from surface waters collected from three Great Lake areas. At each location, three sites (two beaches; one river) were sampled five days a week over the 2015 beach season (n = 609 total samples). In addition, culturable E. coli and enterococci concentrations, as well as 16 water quality and recreational area parameters were assessed such as rainfall, turbidity, dissolved oxygen, pH, and ultra violet absorbance. Overall, somatic coliphage levels ranged from non-detectable to 4.39 log10 plaque forming units per liter and were consistently higher compared to F+ (non-detectable to 3.15 log10 PFU/L), regardless of sampling site. Coliphage concentrations weakly correlated with cultivated fecal indicator bacteria levels (E. coli and enterococci) at 75% of beach sites tested in study (r = 0.28 to 0.40). In addition, ultraviolet light absorption and water temperature were closely associated with coliphage concentrations, but not fecal indicator bacteria levels suggesting different persistence trends in Great Lake waters between indicator types (bacteria versus virus). Finally, implications for coliphage water quality management and future research directions are discussed.
Display omitted
•D-HFUF-SAL allowed for simultaneous measurement of somatic and F+ coliphage.•E. coli and enterococci indicator levels were consistently higher than coliphage.•Coliphage levels weakly correlated with indicator bacteria (r ≤ 0.04) at 75% of beach sites.•Ultraviolet light absorption and water temperature closely associated with coliphage levels.•Water quality and recreational parameters were better predictors of indicator bacteria.
Abstract
A number of prokaryotes are capable of employing arsenic oxy-anions as either electron acceptors arsenate; As(V) or electron donors arsenite; As(III) to sustain arsenic-dependent growth ...(‘arsenotrophy’). A subset of these microorganisms function as either chemoautotrophs or photoautotrophs, whereby they gain sufficient energy from their redox metabolism of arsenic to completely satisfy their carbon needs for growth by autotrophy, that is the fixation of inorganic carbon (e.g. HCO3−) into their biomass. Here we review what has been learned of these processes by investigations we have undertaken in three soda lakes of the western USA and from the physiological characterizations of the relevant bacteria, which include the critical genes involved, such as respiratory arsenate reductase (arrA) and the discovery of its arsenite-oxidizing counterpart (arxA). When possible, we refer to instances of similar process occurring in other, less extreme ecosystems and by microbes other than haloalkaliphiles.
Arsenic can support the growth of a number of microorganisms, some of which carry out arsenic-based chemoautotrophy and photoautotrophy.
Diverse in their languages and customs, the Native American
peoples of the Great Lakes region-the Miamis, Ho-Chunks,
Potawatomis, Ojibwas, and many others-shared a tumultuous history.
In the colonial ...era their rich homeland became a target of imperial
ambition and an invasion zone for European diseases, technologies,
beliefs, and colonists. Yet in the face of these challenges, their
nations' strong bonds of trade, intermarriage, and association grew
and extended throughout their watery domain, and strategic
relationships and choices allowed them to survive in an era of war,
epidemic, and invasion.
In Peoples of the Inland Sea, David Andrew Nichols
offers a fresh and boundary-crossing history of the Lakes peoples
over nearly three centuries of rapid change, from pre-Columbian
times through the era of Andrew Jackson's Removal program. As the
people themselves persisted, so did their customs, religions, and
control over their destinies, even in the Removal era. In Nichols's
hands, Native, French, American, and English sources combine to
tell this important story in a way as imaginative as it is bold.
Accessible and creative, Peoples of the Inland Sea is
destined to become a classroom staple and a classic in Native
American history.
Meromictic lakes located in landlocked steppes of central Asia (~2500 km inland) have unique geophysiochemical characteristics compared to other meromictic lakes. To characterize their bacteria and ...elucidate relationships between those bacteria and surrounding environments, water samples were collected from three saline meromictic lakes (Lakes Shira, Shunet and Oigon) in the border between Siberia and the West Mongolia, near the center of Asia. Based on in-depth tag pyrosequencing, bacterial communities were highly variable and dissimilar among lakes and between oxic and anoxic layers within individual lakes. Proteobacteria, Bacteroidetes, Cyanobacteria, Actinobacteria and Firmicutes were the most abundant phyla, whereas three genera of purple sulfur bacteria (a novel genus, Thiocapsa and Halochromatium) were predominant bacterial components in the anoxic layer of Lake Shira (~20.6% of relative abundance), Lake Shunet (~27.1%) and Lake Oigon (~9.25%), respectively. However, few known green sulfur bacteria were detected. Notably, 3.94% of all sequencing reads were classified into 19 candidate divisions, which was especially high (23.12%) in the anoxic layer of Lake Shunet. Furthermore, several hydro-parameters (temperature, pH, dissolved oxygen, H2S and salinity) were associated (P< 0.05) with variations in dominant bacterial groups. In conclusion, based on highly variable bacterial composition in water layers or lakes, we inferred that the meromictic ecosystem was characterized by high diversity and heterogenous niches.
PDF
