Similar Physicochemical Conditions Research Articles

Comprehensive research of the distribution of tellurium-bismuth mineralization in the ores of the Abyz and Maleevskoe sulfide deposits (Republic of Kazakhstan)

Abstract. Within the formations of ensimatic and ensialic island arcs in the territory of Central and Northern Kazakhstan, there are more than thirty pyrite deposits enriched in copper, lead, zinc, gold, silver and rare metal mineralization, which is still insufficiently studied. Relevance. The need to replenish information on tellurium-bismuth mineralization in ores of sulfide deposits formed in ensimatic (Abyz deposit) and ensialic (Maleevskoe deposit) island-arc systems, to establish a spatial connection of this type of mineralization with geodynamic conditions and predict the potential for their associated extraction from ore. Aim. To study and compare morphological characteristics, distribution patterns and conditions for the formation of tellurium-bismuth mineralization in ores of pyrite deposits formed in different island-arc geodynamic settings. Methods. Inductively coupled plasma mass spectrometry, mineragraphic and mineralogical analyses, scanning electron microscopy in combination with X-ray spectral microanalysis, Raman spectroscopy, thermobarogeochemical studies. Results. A comparison of the pyrite deposits of the Rudno-Altai and Chingiz-Tarbagatai island arc systems showed many similarities and differences between them. The deposits have a multi-stage formation and a similar mechanism of ore deposition with similar physicochemical conditions for the formation of tellurium-bismuth mineralization. A spatial relationship between Te-Bi mineralization and geodynamic settings was established: for deposits associated with paleooceanic structures, a predominance of the tellurium element is observed, and for continental rifts, a predominance of the bismuth element.

Evolution of an ancient VMS ore-forming system recorded by pyrite and sphalerite mineral texture, trace elements, and sulfur isotope: A case study from the Huangtupo Cu-Zn (-Au) deposit, Eastern Tianshan, NW China

The Huangtupo Cu-Zn (-Au) volcanogenic massive sulfide deposit is hosted in a suite of Early Paleozoic basic to acidic volcanic, volcaniclastic rocks in the Eastern Tianshan orogen, northwest China. The Cu-Zn orebodies are characterized by the zoning of metallogenic elements upward from a deep stockwork mineralized zone (Cu > Zn) to a shallow massive mineralized zone (Zn > Cu). Detailed petrographic and LA-ICP-MS analyses have identified five types of pyrite and three types of sphalerite. These sulfides can be distinguished in a paragenesis with four stages of sulfide mineralization. The preore stage (SⅠ) from the deep volcanic rock contains subhedral-euhedral pyrite (Py1) with high trace element contents (e.g., Co, Ni, and Ti; Average value of total trace elements: 16764 ppm), except for Sb, and Tl, indicating a euxinic and high-temperature environment. Both the disseminated and veined pyrite (Py2) from the early ore stage (SⅡ; stockwork zone) and the euhedral pyrite (Py3) from the main ore stage-1 (SIII-1) have a similar chemical signature, suggesting that they precipitated under similar physicochemical conditions. These two paragentic stages of pyrite contributed only minimally to the trace elements endowment, except for higher Se contents. The continuous convection of hydrothermal fluids caused a large accumulation of copper and zinc, forming massive orebodies. Pyrite within the Zn(Cu)-rich zone of the main ore stage-2 (SIII-2) comprises three sub-generations (Py4a ∼ c) which are characterized by enrichment in most trace elements such as Au, As, Cu, and Sb. Pyrite 4a ∼ c formed in a fluctuating sedimentary environment and recorded the injection of a short-term, gold-rich fluid, which dissolved and reprecipitated trace elements from earlier ores and surrounding rocks. Orebody deformation and local metamorphism played a key role in this gold enrichment event. Pyrite (Py5) from the late ore stage (SⅣ) is deficient in most elements but relatively enriched in Co, Ni, and Se. Three stages of sphalerite associated with the Py3 ∼ 4 have been distinguished in the SIII. From Sp1 to Sp3, the content of Fe, Ge, Mo, and Cd decreased gradually, but the Sp2 is relatively depleted in Ag, As, Au, Pb, and Sb compared to Sp1 and Sp3. The sensitive variation of As, Co, Ni, Se, Pb in pyrite and Fe, Cu, Mn, Sb, Cd in sphalerite provide significant information for reconstructing the hydrothermal evolution process. The sulfur isotopes of these pyrites determined by in situ LA-multicollector (MC)-ICP-MS analyses are concentrated around 0‰, but vary significantly from −2.3 to 5.8‰. The δ34S values of the sphalerite range from −3.5 to 4.0 ‰ and tends to decrease from Sp1 to Sp3. These results show that the metals of the SIII were most likely derived from the deep-seated Early Paleozoic subvolcanic intrusion and Daliugou Formation during the evolution of regional island arcs.Combining the chemical, and isotopic data and geological features, the ore-forming process of an ancient VMS deposit was deduced. These results constrain the texture, composition and sulfur isotopic signatures of sulfides in veins and deformed ore bodies, as well as the gold enrichment mechanism, and also reflect the vertical variation of trace elements at the scale of VMS deposits, supporting the existence of multiple depositional mechanisms.

Comparison of rosette-shape traces in abyssal terrains: Environmental and faunal implications

Biogenic traces (lebensspuren) result from the activity of benthic organisms on and within the seafloor and are a common feature of deep-sea environments. Rosette-shape traces (RSTs), also referred to as spoke burrows, are a commonly observed and distinctive trace, likely created by echiuran worms during feeding and burrowing. We conduct a quantitative morphometric assessment of RSTs from two contrasting sites at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO; Northeast Atlantic) with similar physico-chemical conditions except for relative sediment compaction, but substantive differences in their megabenthic communities. We quantified RST abundance (numerical density and seafloor cover) and morphological characteristics (spoke number and overlap, spoke length and width, trace area and relative completeness) for 148 individual RSTs observed in some 6800 seafloor photograph (8788 m−2 seafloor area) captured with an autonomous underwater vehicle. We derived two primary results between study sites: (a) individual spoke morphology exhibited no statistically significant differences, while (b) individual trace completeness was significantly different. The consistency in spoke morphometrics reflects our identification of a single RST morphotype, potentially representing a single functional group of echiurans. The difference in trace completeness between sites may have resulted from differences in competition for resource with other megabenthic surface deposit feeders, and not to be directly related to relative sediment compaction. By reference to literature data and observations of similar traces in other deep-sea settings, we further suggest that this connection between trace completeness and resource availability may be more generally applicable in both contemporary ecology and paleoichnology.

EVALUATION OF POLYUNSATURATED FATTY ACIDS AND β-GLUCAN CONTAINING DIET ON GROWTH PERFORMANCE AND CONDITION FACTOR OF PABDAH CATFISH, OMPOK PABDA (HAMILTON, 1822)

Nutritionally balanced diet and selection of appropriate species for culturing environment are important criteria in aquaculture. The present study was conducted to evaluate the effects of polyunsaturated fatty acids (PUFAs) and β-glucan containing diet (PBG) on growth performance, feed utilization, length-weight relationship, and condition factor of Pabdah catfish, Ompok pabda. In this study, squid extracted phospholipid and mushroom powder were used as the source of PUFAs and β-glucan, respectively, and formulated two isonitrogenous diets such as basal or control (CON) diet and PBG diet with maintaining 30% protein levels. During the study period, similar physicochemical conditions of water such as temperature, pH, and dissolved oxygen (DO) were 26.5 ± 2 °C, 7.4 ± 0.2, and 6.7 ± 0.5 ppm, respectively were maintained in each cistern. The results showed that final mean body weight, final mean length gain, food conversion ratio (FCR), specific growth rate (SGR), food conversion efficiency (%), hepato somatic index (HSI), kidney index (KI), and viscerosomatic index (VSI) were significantly (P<0.01 and P<0.05) higher in fish fed the PBG diet than that of fish fed the CON diet. The coefficient of determination showed a significant relationship (R2 = 0.956) between the length and weight of the treatment group. The length-weight relationship and relative condition factor (K) of Ompok pabda were significantly (P<0.05) affected by the PBG diet. The present study shows that the experimental diet more effective and achieves better growth performance, feed utilization, length-weight relationship, and condition factor of Ompok pabda.

Environmental Heterogeneity Determines Diatom Colonisation on Artificial Substrata: Implications for Biomonitoring in Coastal Marine Waters

Benthic diatoms form an important component of the microphytobenthos and have long been utilised as suitable bioindicators in aquatic systems. However, knowledge on benthic diatom community succession on hard substrata (biofilm) remains understudied in austral marine coastal systems. In this study, we investigated benthic diatom colonisation on artificial substrates (Plexiglass) over a period of 5 weeks at two locations with different physical environments along the warm temperate coast of South Africa. Results revealed relatively similar physico-chemical conditions but highly contrasting diatom community development were observed between the two sites. While there were some shared taxa, site-specific dynamics resulted in significantly different diatom species diversity and richness, facilitated by common (e.g., Nitzschia ventricosa and Cocconeis scutellum) and a large percentage of rarely observed species such as Cocconeis testudo and Lyrella lyra. A total of 134 species belonging to 44 genera were observed during the study. The overall diatom composition differed spatio-temporally during the experimental period, with the fluctuating species occurrences and abundances highlighting the rapid microalgal species turnover within days, under natural conditions. Environmental variables were shown to have varying influences as drivers of the diatom community descriptors. Multivariate modelling confirmed that study site and the interaction between site and sampling occasion were important predictors of diatom abundances, and the overall observed community composition. The current results suggest that benthic diatoms on artificial substrata could be incorporated as suitable indicators of change along the coastline subject to further investigations, taking into account site-specific differences driven by habitat complexity and environmental variability. The experimental method proved to be efficient and can be implemented to study the response of benthic diatoms to localised nutrient enrichment around the coastline.

Biodiversity and seasonal distribution of benthic diatom assemblages as an indicator of water quality of small karstic river in Bosnia and Herzegovina

The aims of this paper were to describe seasonal changes in the qualitative and quantitative composition of diatom taxa and the potential application of benthic diatoms for ecological status evaluation. Diatom indices (IPS and TI) were calculated from data from three different locations along a longitudinal profile of the Bunica, a small karstic river in Bosnia and Herzegovina. A total of 147 taxa were recorded in 12 samples. The most common taxa were Meridion circulare (Greville) C.Agardh and Ulnaria ulna (Nitzsch) Compère. Physical and chemical analyses showed low concentrations of nutrients, good oxygenation, typical pH for carbonate bed/origin and generally oligotrophic conditions and high ecological status. All sites had similar physico-chemical conditions and there were only few seasonal differences. Ordination of the diatom data showed that samples showed neither longitudinal nor seasonal patterns. Median value for IPS (16.8) and for TI (7.3) can be possible ‘‘expected’’ values for ecological status assessment for small karstic rivers in the Mediterranean region. We propose the use of the phytobenthos Intercalibration Common Metric (pICM - an index that combines the IPS and TI) as a national metric for countries developing WFD diatom methods at a late stage. One situation is described, and a solution, which is potentially transferable to other locations in Bosnia and Herzegovina and also to other countries facing similar challenges.

Constraints on fluid evolution and growth processes of black smoker chimneys by pyrite geochemistry: A case study of the Tongguan hydrothermal field, South Mid-Atlantic Ridge

Up to now, the Tongguan hydrothermal field is the southernmost-distributed modern submarine massive sulfide discovered on the South Mid-Atlantic Ridge. A well-preserved black smoker chimney which contains three distinct concentric zones was collected from the active vent field. The external outer wall of the chimney contains mainly pyrite with minor sphalerite, chalcopyrite and galena. The sulfides within the internal middle layer consist of predominant pyrite, with lesser amounts of marcasite. The axial conduit is dominated by chalcopyrite, with minor pyrite. To clarify the ore-forming fluid evolution during the black smoker chimney growth, we performed detailed petrographic and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) studies on pyrite grains from the chimney. Seven types of pyrite: framboidal, relict, colloform, dendritic, massive, euhedral and lined pyrites, are identified from exterior to interior of the chimney.As shown by the results of LA-ICPMS, geochemical compositions of pyrite vary across the chimney. Generally, low-temperature elements (Mg, V, Mn, Pb, Zn, Ag and Tl) are enriched in pyrite in the outer wall of the chimney and decrease toward the interior zones. Elements indicative of high temperature conditions, such as Se and Te, show opposite trends and are enriched in pyrite within the inner zones of the chimney. Framboidal, relict, colloform and dendritic pyrites precipitate from low to mid temperature fluids (<250 °C), while massive and euhedral pyrites are products of ore-forming fluids characterized by mid to high temperature (250 to > 335 °C). Relict and lined pyrites have the same chemical signatures, suggesting that they precipitated under similar physicochemical conditions. The observed patterns are resulted from the changes in temperature and fluid chemistry caused by interactions of between seawater and hydrothermal fluids with each other in the chimney.Cobalt concentrations in pyrite from the modern black smoker chimneys located on the mid-ocean ridge apparently vary systematically in response to salinity change of vent fluids. The low Co contents (average 0.32 ppm) in pyrite suggest that the hydrothermal fluids vented from the black smoker chimney are Cl-depleted compared to seawater, most likely caused by phase separation. The systematic variations in geochemistry and morphology of the pyrite across the chimney reflect multiple stages of mineralization. Different degrees of fluid-seawater mixing and phase separation are the main controlling factors during the chimney formation.

Dolomitization micro-conditions constraint on dolomite stoichiometry: A case study from the Miocene Huangliu Formation, Xisha Islands, South China Sea

The micro-conditions that control dolomitization processes were still not well known in natural environments. Cenozoic “island dolostones” are ideal for examining the processes since they are geologically young and have not experienced deep burial conditions. Miocene dolostones from the Xisha Islands, located in the South China Sea, are similar to those found on Grand Cayman Island, located in the Caribbean Sea. These dolostones are composed of low-Ca dolomite (LCD, < 55 mol % CaCO3; hereafter referred to as %Ca) and high-Ca dolomite (HCD, > 55 %Ca). Individual dolomite crystals are commonly formed entirely of LCD or HCD, and/or HCD cores that are encased by LCD and alternating zones of HCD and LCD (1–10 μm thick). The crystal textures indicate that the LCD and HCD are primary growth features (no obvious recrystallization) that formed as the dolomite replaced the limestone precursor. The compositional features (%Ca in LCD and HCD, average %Ca, and proportion of LCD and HCD) and geochemical parameters (O/C isotopes, Sr, Fe and Mn) of dolomite indicate that the Mg was incorporated into dolomite crystals in an orderly manner that was mainly controlled by the interaction of fluid properties and crystal structure. The fact that dolomite stoichiometry varied laterally and vertically throughout the successions shows that micro-scale physicochemical conditions played a critical role in the evolution of individual dolomite crystals. The similarities between the dolostones of the Xisha Islands and Grand Cayman, which are 15,795 km apart, indicate that the factors that control the micro- and large-scale features of these dolostones must have undergone similar processes or experienced similar physicochemical conditions despite their disparate settings.

Surface Water Quality Differs between Functionally Similar Restored and Natural Wetlands of the Saint Lawrence River Valley in New York

We tested the hypothesis that upland wetland restorations provide the same quality of wetland, in terms of ecosystem services and biodiversity, as natural wetlands in the St. Lawrence River Valley. Water quality (pH, alkalinity, colored dissolved organic matter, phytoplankton community composition, chlorophyll-a, fecal coliform, total phosphorus, dissolved nitrate, turbidity, specific conductivity) in 17 natural and 45 restored wetlands was compared to determine whether wetland restoration provided similar physicochemical conditions as natural wetlands in the Saint Lawrence River Valley of northeastern New York State. Natural wetlands were more acidic, which was hypothesized to result from the avoidance of naturally acidic regions by farmers seeking to drain wetlands for crop and pasture use. Natural wetlands had significantly greater fecal coliform concentrations. Restored wetlands had significantly greater specific conductivity and related ions, and this is attributed to the creation of wetlands upon marine clay deposits. Other water quality indicators did not differ between restored and natural wetlands. These findings confirm other research at these same wetlands showing no substantial differences between restored and natural wetlands in major biotic indicators. Thus, we conclude that wetland restoration does result in wetlands that are functionally the same as the natural wetlands they were designed to replicate.

The magmatic–hydrothermal evolution of the San Pedro porphyry Cu‐(Mo) deposit: Implications for the metallogenesis of the Permian magmatism in the western margin of Gondwana

AbstractThe San Pedro porphyry Cu‐(Mo) deposit, located in the San Rafael Massif (Argentina), is characterized by multiple stockwork vein generations developed in a subvolcanic intrusion with porphyry‐type alteration and mineralization, as well as associated polymetallic veins. Previous works reveal that the intrusive rocks related to the San Pedro porphyry (263 Ma) show comparable trace element signatures to giant porphyry deposits elsewhere (i.e., high Sr/Y and low Y). The fluid inclusions investigated in this study show that typical early, high‐temperature magmatic fluids (up to 685°C; 81.3 wt% equiv. NaCl) evolved to lower‐temperature, moderately saline fluids (up to 454°C; 52.4 wt% equiv. NaCl) due to fluid–rock interaction. The waning stage of the system is characterized by secondary, aqueous inclusions that represent dilution by meteoric fluids (up to 390°C, 16.9 wt% equiv. NaCl). Fluid inclusions were studied from two veinlet generations (A and B veinlets) related to potassic alteration and analyzed by LA‐ICP‐MS. The trace element signatures in the fluid inclusions suggest that there were two pulses of magmatic fluids that subsequently evolved under similar physicochemical conditions. The Cu concentration in the earliest fluid is between 0.3 and 0.85 wt% and within the concentrations found in other mineralized porphyry systems in the world. However, in contrast to economic porphyry systems, where a significant change in Cu concentration during fluid evolution is observed, there is no distinct change in the fluid Cu concentration at the San Pedro deposit, which would indicate that Cu and Mo precipitation was ineffective in the hydrothermal system.

Environmental factors affecting the nursery function for fish in the main estuaries of the Gulf of Cadiz (south-west Iberian Peninsula)

Hydrological, geomorphological, physicochemical and biological factors influence the nursery function of estuaries. Our study compared the environmental conditions and the assemblages of early life stages of fish in the main four estuaries of the Gulf of Cadiz (Cadiz Bay, Guadalquivir, Odiel-Tinto and Guadiana). Samples were taken within each estuary and on their adjacent coast, during the dry-warm seasons of 2016, 2017 and 2018. Results showed that rivers with smaller basins had a very low freshwater input and their estuaries, Odiel-Tinto and Cadiz Bay, were essentially sea extensions into the land, containing similar physicochemical conditions to nearshore zones, as well as similar assemblages and densities of early life stages of fish. Open water masses of these estuaries do not have important nursery functions. In contrast, inner zones of estuaries with bigger basins and higher freshwater discharges, Guadalquivir and Guadiana, have different environmental characteristics and a long transition zone with a well-defined salinity gradient. Their assemblages and densities of early life stages of fish were different between them and with other estuaries. The Guadalquivir estuary held the highest abundance of larval and early juvenile fish, as well as macrozooplankton biomass. The most abundant fish species in all zones of every estuary was the anchovy Engraulis encrasicolus; the Guadalquivir inner zone had the highest density. High concentration of suspended organic matter, provided by freshwater input and correlated with total suspended solid, suspended inorganic matter and turbidity, was the physicochemical characteristic more typical of the Guadalquivir. This characteristic, in addition to the salinity gradient, could explain the highest densities of macrozooplankton found in this estuary, and consequently, of early fish stages. Recurrent jellyfish blooms were observed in Cadiz Bay and the inner zone of Guadiana, affecting their nursery functions. Odiel-Tinto showed altered physicochemical and biological characteristics, which may need further specific research.

Ore-forming processes in the Wang’ershan gold deposit (Jiaodong, China): Insight from microtexture, mineral chemistry and sulfur isotope compositions

The microtexture, trace element characteristics and sulfur isotopic features of ore-related minerals provide important clues to trace physico-chemical conditions and source characteristics of ore formation. In this study, we investigate the Wang’ershan gold deposit in the Jiaodong gold province of eastern North China Craton where three hydrothermal stages were distinguished. Stage I is characterized by K-feldspar, sericite, quartz with minor pyrite precipitation (Py-I); sericite, quartz (Qtz-a) and pyrite (Py-II) with minor gold precipitated during stage II; and stage III involved quartz (Qtz-b), gold, and polymetallic sulfides with minor pyrite (Py-III). In situ δ34S results show a decreasing trend from 21.7 to 14.6‰ (Py-I) to 9.2–8.3‰ (Py-II) and 8.9–8.6‰ (Py-III). The Py-II and Py-III are poor in mineral inclusions and porous microtextures, and have no oscillatory composition zoning. The Co content is 1–2 order of magnitudes higher in Py-I (371.2 – 823.2 ppm, av. 597.2 ppm) than late stage pyrites (0.4 – 524.2 ppm, av. 95.4 ppm). Qtz-a show cataclastic breccia cemented by Qtz-b with little dissolution during the injection of stage III ore-forming fluids. The Al contents decrease from Qtz-a (49.0 – 426.6 ppm) to Qtz-b (18.2 – 46.8 ppm). Based on the sulfur isotope, trace element and microtextural characteristics in Py-II and Py-III, combined with previous fluid inclusion studies, we infer that the ore-forming fluids of stage II and III experienced gentle immiscibility and were suggested to be of different evolutionary stages of a single ore-forming fluid sharing common sources with similar and near-equilibrium physicochemical conditions. The trace element characteristics with lack of oscillatory compositional zoning in the two stages of quartz suggest gentle cooling with lack of any abrupt change of physicochemical conditions during fluid immiscibility. The decoupling of Au and As contents in Py-II and Py-III was likely controlled by chemisorption of gold in pyrite structure. Complex variation in geochemical features of ore-forming fluids from early alteration to main mineralization period is indicated by the large range of δ34S and Co contents in Py-I and late stage pyrites, and the differences in alteration processes. Based on a comparison of the Co/Ni, Ni and As among pyrites from the Wang’ershan gold deposit, typical porphyry deposits and orogenic gold deposits, together with the large positive deviation of δ34S relative to mantle values, we propose that ore-forming materials of the Wang’ershan gold deposit were derived from mixed sources involving magmatic hydrothermal-related and sedimentary strata-related components.

Analogous diagenetic conditions of dark enclave and its host granite derived by magma mixing: Evidence for a post-mixing magmatic process

Mafic microgranular enclaves (MMEs) are commonly formed during magma mixing and usually record contrasting physicochemical diagenetic characteristics relative to their host rocks. We present a finding that some MMEs from the Cretaceous Qianjia pluton, which is believed to be the product of magma mixing, exhibit diagenetic conditions analogous to those of their host granites. Integrated calculations based on in situ compositions of minerals (e.g., zircon, titanite, amphibole, feldspar, and apatite) from the Qianjia monzonitic MMEs and their host granites indicate that they exhibit similar diagenetic temperatures (700–800 °C) and pressures (0.20–0.28 GPa), but discrepant oxygen fugacity and water activity. The MMEs have higher oxygen fugacity and water activity, as well as lower Th/U ratios, compared to the host granites, suggesting more oxidized and H2O-rich circumstances. Besides, high F concentrations and F/Cl ratios in apatites from both the MMEs and host granites and their parent magma indicate a relatively F-rich magma source that was probably derived by F-bearing mineral dehydration during plate subduction. Similar physicochemical diagenetic conditions between the MMEs and their host granites seemingly reveal their cognate features; however, slight differences in the oxygen fugacity, water activity, and chemistry of certain minerals (e.g., apatite and titanite) provide clues on magma mixing. We therefore propose that the MMEs involved might have been derived from local heterogeneous hybrid melts or by early crystallization during a post-mixing process. In this case, information about the magma mixing has been almost eliminated due to the geochemical re-equilibration. Therefore, in the case of magma-mixing derived intrusions, the MMEs could be formed not only during magma mixing but also during a post-mixing stage, in which certain minerals most likely preserved a few geochemical characteristics of magma mixing.

Spatio-temporal variation of cyanobacteria and cyanotoxins in public supply reservoirs of the semi-arid region of Brazil

Cyanobacteria harmful algal blooms (CyanoHABs) have become increasingly frequent and intense in public supply reservoirs as a result of eutrophication and global climate change. The semi-arid region of Brazil has a well documented history of CyanoHABs but the underlying factors that control the excessive proliferation of these organisms and the production of their bioactive secondary metabolites are not comprehensively understood. This study aimed to identify the environmental factors that explain the spatial and temporal variations in the abundance of cyanobacteria and the concentration of cyanotoxins (microcystins, saxitoxins, and cylindrospermopsin) in semi-arid reservoirs. The following hypotheses were tested: (a) the largest biovolumes of potential toxin producing cyanobacteria occur when cyanotoxin concentrations are highest; and (b) the environmental factors that explain variations in biovolume of cyanobacteria also explain changes in cyanotoxins concentrations. Samples were taken from four reservoirs located in the Northeast region of Brazil, over a three-month period (October 2016 and February and June 2017). Of the 24 species of cyanobacteria identified, 13 were potentially toxin-producing. Physicochemical variables such as water volume of the reservoir, water transparency, soluble reactive phosphorus, and total phosphorus explained the abundance of cyanobacteria and the levels of cyanotoxins. These results corroborate the hypothesis that similar physicochemical conditions influence the abundance and diversity of cyanobacteria and cyanotoxins. Cyanobacterial blooms composed of more than one potential toxin producing species were observed in the studied reservoirs, where potential microcystin-producing species were the most common. Microcystins and saxitoxins were detected in all the reservoirs studied, while cylindrospermopsin and the cyanobacterium Cylindrospermopsis raciborskii were simultaneously recorded in only one reservoir (Camalaú Reservoir). Cylindrospermopsin was only detected in a reservoir for the first time in the State of Paraíba. Canonical redundancy analysis showed that the cyanotoxins were related to potential toxin producing species. These results corroborate the proposed hypothesis that there is a correlation between cyanotoxins and the biomass of potential producers. Also, there were situations where cyanotoxins were detected without the presence of potential producers. These results demonstrate the need for reassessment of potential toxin producing species of cyanobacteria in semi-arid reservoirs. This may lead to the identification and characterization of novel producers of these bioactive secondary metabolites.

Extremely acidic environment: Biogeochemical effects on algal biofilms

The biological responses of acidobiontic species to extremely acidic waters, as those related with Acid Mine Drainage (AMD) processes, are relevant not only to understand the toxicological degree of the waters as well as the mechanisms responsible for the survival and adaptation of such organisms.Therefore, the objective of this study was to evaluate the effect of acidic pH and metals in biofilms collected in two sites a lentic permanent acid pond (AP) and a temporary acid stream (AS) affected by Acid Mine Drainage (AMD), and taking as control (C), an uncontaminated site with circumneutral pH. The results showed typical conditions of AMD-contaminated waters in sites AS and AP (pH < 3 and high concentrations of Al, Cu, Fe, Mn, Pb and Zn), which are responsible for a substantial decrease in biomass and biodiversity of biofilms (with a dominance of acidobiontic species, such as Pinnularia aljustrelica and Eunotia exigua, comparing to the control site. Also expressed by low values of photosynthetic pigments and reduced amount of proteins. In addition, such extreme acidic conditions also induced biofilms’ stress, increasing antioxidant [catalase (CAT), superoxide dismutase (SOD) and biotransformation glutathione S-transferases (GSTs)] enzymes activity and also membrane damage (peroxidized lipids). However, despite the quite similar physico-chemical conditions of both AMD-contaminated sites, differences in the toxicity status between them were indirectly detected through some of the biochemical parameters [GSTs, SOD and CAT], indicating site AS has the most toxic, which fact was attributed to the higher concentrations of Pb2+ in this water. This element is recognized to be highly toxic for biota, and in such acidic conditions remains in solution, easily available to the aquatic organisms. Since pH is similar in the acid sites, the different concentrations of heavy metals in the waters might be responsible for the observed changes in the biological community at these two sites.This fact was translated in a higher capacity of this site's biofilm to cope with the negative effects of the toxicants, evidenced in a higher positive correlation with GSTs, CAT and SOD when compared to biofilms of sites AP and C.

Potential Functions of the Gastrointestinal Microbiome Inhabiting the Length of the Rat Digest Tract

The rat is an important model animal used frequently in biological researches exploring the correlations between gut microbiome and a wide array of diseases. In this study, we used an extended ancestral-state reconstruction algorithm to predict the functional capabilities of the rat gastrointestinal microbiome. Our results indicate an apparent tendency toward metabolic heterogeneity along the longitudinal and transverse axes of the rat gastrointestinal tract (GIT). This heterogeneity was suggested by the enriched small-molecule transport activity and amino acid metabolism in the upper GIT, the aerobic energy metabolism in the stomach and the mucolysis-related metabolism in the lower GIT mucus layer. In contrast to prior results, many functional overlaps were observed when the gastrointestinal microbiomes of different hosts were compared. These overlaps implied that although both the biogeographic location and host genotype were prominent driving forces in shaping the gastrointestinal microbiota, the microbiome functions were similar across hosts when observed under similar physicochemical conditions at identical anatomical sites. Our work effectively complements the rat microbial biogeography dataset we released in 2017 and, thus, contributes to a better understanding and prediction of disease-related alterations in microbial community function.

CO2—H2O Capture and Cyclability on Sodium Cobaltate at Low Temperatures (30–80 °C): Experimental and Theoretical Analysis

Sodium cobaltate (NaCoO2) is analyzed for the CO2 cyclic carbonation–decarbonation process at low temperatures (30–80 °C) with relative humidity (RH) values between 0% and 80%, using water vapor as a catalytic intermediate. The presence of H2O clearly enhances the CO2 capture at T &lt; 100 °C, compared with dry conditions, where the amount of CO2 captured increases as a function of RH. These improvements are attributed to the formation of NaHCO3 and Na2CO3 during carbonation. In the case of NaHCO3, water vapor becomes a part of carbonation, favoring reactivity. After the carbonation analysis, the decarbonation process is analyzed using a N2 flow, where results evidence that only NaHCO3 decomposition takes place at low temperatures, producing NaOH and CO2. This result indicates that NaCoO2 can be partially regenerated, suggesting a possible CO2 cyclic carbonation. CO2 carbonation–decarbonation tests are performed, confirming the cyclic capacity and stability. Moreover, the NaCoO2 sample is modified by adding different transition metals (Fe, Cu, and Ni) to improve CO2—H2O sorption under similar physicochemical conditions. Results indicate that Fe‐containing samples present the best properties. Finally, the effect of CO2 partial pressure on NaCoO2 and Fe‐containing samples is analyzed using similar RHs.

Amaranth and wheat grains tested as nucleation sites of microbial communities to produce bioflocs used for shrimp culture

The taxonomy profiles of bacterial communities contained in bioflocs produced with amaranth (BFT_Amaranth) and wheat (BFT_Wheat) grains as substrates, and used for shrimp culture were evaluated. The proliferation of heterotrophic bacteria was promoted by maintaining a carbon:nitrogen ratio of 12:1. High throughput sequencing of the 16S-rRNA gene revealed that the maximum difference between BFT_Amaranth and BFT_Wheat was registered at the beginning of the trial, when BFT_Wheat was dominated by Bacteroidetes (80–85%), whereas BFT_ Amaranth was dominated by Planctomycetes (42%), Proteobacteria (26%) and Bacteroidetes (16%). However, the taxonomic profile of both biofloc types were similar at the end of the trial, suggesting that the type of substrate affected the initial biofouling process, but the similar physicochemical conditions maintained during the trial favored the same heterotrophic communities in both treatments; herein, only 97 were shared between BFT_Wheat and BFT_Amaranth at the beginning of the trial, but 185 at the end. Thereafter, a better productive response in terms of survival, growth rate and FCR was registered for shrimp reared with BFT_Wheat, which corresponded to the biofloc registering the highest protein content at the end of the trial (18.5%), compared to BFT_Amaranth (12.7%). Finally, despite the high similarity detected among both biofloc types, this may not be strongly associated with their nutritional composition, nor the massification rate of these microbial communities.

Variation among macroinvertebrate communities suggests the importance of conserving desert springs

Abstract Desert springs are highly threatened ecosystems inhabited by a substantial number of endemic species. Macroinvertebrate communities of five springs in the northern Chihuahuan Desert of west Texas and south‐eastern New Mexico were sampled seasonally. Rather than focusing on individual taxa, this study examined the community structure of springs to identify patterns that are likely to reflect both local conditions and potential dispersal barriers. In total, 46 774 individuals representing 109 taxa were collected with high relative abundances of gastropods, amphipods, and oligochaetes. Spatial variation in community composition was greater than temporal variation. Although there were differences in the salinity content and concentrations of several major anions and cations among sites, these were not significant predictors of difference in community structure. Two springs sharing the same groundwater source contained similar macroinvertebrate communities and had similar physicochemical conditions. Results from this study suggest that springs in the northern Chihuahuan Desert contain unique communities and endemic species owing to historical processes such as isolation and dispersal limitation, rather than contemporary processes such as environmental filtering and species sorting. Springs located in the northern Chihuahuan Desert, like those located in other arid regions of the world, are valuable for their biodiversity because of their distinct invertebrate communities and high rates of endemism. Thus, they should be conserved individually to ensure the preservation of unique species and communities.

Deciphering the Hydrothermal Evolution of a VMS System by LA-ICP-MS Using Trace Elements in Pyrite: An Example from the Bracemac-McLeod Deposits, Abitibi, Canada, and Implications for Exploration

Textural and chemical characterization of pyrite was used to reconstruct the hydrothermal evolution of the Bracemac-McLeod Archean volcanogenic massive sulfide (VMS) deposits (~6 Mt) in the Matagami district, Abitibi, Canada. The mineralization, hosted in a bimodal volcanic sequence, is divided into a (1) Zn-rich zone, concordant to the Key Tuffite— a marker horizon at the district-scale, 2) a Cu-rich zone which locally crosscuts the stratigraphic pile, and 3) some localized magnetite-rich zones replacing sphalerite and pyrite. Detailed petrographic and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) studies of whole pyrite grains (including inclusions and zonation) from the Key Tuffite and from the different ore zones of the deposits, has revealed five pyrite types. Nodular pyrites (I) in the Key Tuffite and subidiomorphic pyrites from the low temperature (250°C) Zn-rich zone (II) have the same chemical signature, suggesting that both precipitated under similar physicochemical conditions. A wide range of trace elements (Cu, Zn, Ag, Sn, Sb, Te, Au, Pb, Bi, Tl) are present in both, but compared to the other types of pyrite, they are significantly enriched in Sb and Tl. Subidiomorphic pyrites from the copper-rich zone (III) have a different signature, enriched only in Se ± Co, In, Pb, and Bi. These pyrites commonly overgrow the nodular pyrites and are related to later higher-temperature fluids (300°C). Pyrite preserved during a later magnetite-replacement (>350°C) stage (IV) also are enriched in Se, but are depleted in all other elements. A similar signature is found in idiomorphic metamorphic pyrite (V), which occurs at the district scale. During high temperature recrystallization of pyrite IV and V, only the contents of Ni, Co, As, and Se are mostly preserved, whereas other base metals are expelled from the pyrite structure. Consequently, only Ni, Co, As, Se, Sb, and Tl were useful to reconstruct the hydrothermal evolution of the VMS system and used to build a suite of discrimination diagrams. Specifically, the ratio Se/Tl can discriminate pyrites from mineralized Zn-rich zone (Se/Tl 10,000). The innovative approach of this study, based on LA-ICP-MS acquisition of the chemistry of entire pyrite grains, makes our results directly applicable for exploration. Consequently, pyrite concentrate samples, analyzed for As, Tl, and Se by more classical mass-spectrometric techniques, have the potential to be used for vectoring to ore by using the proposed discrimination diagrams.