Biomass Decay Research Articles

Quantification of Mixed-Layer Clays in Multiple Saturation States Using NEWMOD2: Implications for the Potassium Uplift Hypothesis in the SE United States

AbstractQuantification of mineral assemblages in near-surface Earth materials is a challenge because of the often abundant and highly variable crystalline and chemical nature of discrete clay minerals. Further adding to this challenge is the occurrence of mixed-layer clay minerals, which is complicated because of the numerous possible combinations of clay layer types, as defined by their relative proportions and the ordering schemes. The problem of ensuring accurate quantification is important to understanding landscape evolution because mineral abundances have a large influence on ecosystem function. X-ray diffraction analysis of the variable cation-saturated clay fraction in soil and regolith from the Calhoun Critical Zone observatory near Clinton, South Carolina, USA, was coupled with modeling using NEWMOD2 to show that mixed-layer clays are often dominant components in the mineral assemblages. Deep samples in the profile (>6.5 m) contain mixed-layer kaolinite/smectite, kaolinite/illite-like, kaolinite-vermiculite, illite-like/biotite, and illite-like/vermiculite species (with ‘illite-like’ defined herein as Fe-oxidized 2:1 layer structure with a negative layer charge of ~0.75 per unit formula, i.e. weathered biotite). The 2:1 layers in the mixed-layer structures are proposed to serve as exchange sites for K+, which is known to cycle seasonally between plant biomass and subsurface weathering horizons. Forested landscapes have a greater number of 2:1 layer types than cultivated landscapes. Of two nearby cultivated sites, the one higher in landscape position has fewer 2:1 layer types. Bulk potassium concentrations for the forested and two cultivated sites show the greatest abundances in the surface forested site and lowest abundance in the surface upland cultivated site. These observations suggest that landscape use and landscape position are factors controlling the mixed-layer mineral assemblages in Kanhapludults typical of the S.E. United States Piedmont. These mixed-layer clays are key components of the proposed mechanism for K+ uplift concepts, whereby subsurface cation storage may occur in the interlayer sites (with increased negative 2:1 layer charge) during wetter reduced conditions of the winter season and as biomass decay releases cation nutrients. Cation release from the mixed-layer clays (by decreased 2:1 layer charge) occurs under drier oxidized conditions during the growing seasons as biota utilize cation nutrients. The types and abundances of mixed layers also reflect long-term geologic factors including dissolution/alteration of primary feldspar and biotite and the subsequent transformation and dissolution/precipitation reactions that operate within the soil horizons. Thus, the resulting mixed-layer clay mineral assemblages are often complex and heterogeneous at every depth within a profile and across landscapes. X-ray diffraction (XRD) assessment, using multiple cation saturation state and modeling, is essential for quantifying the clay mineral assemblage and pools for cation nutrients, such as potassium, in the critical zone.

Biological purification of acidic Fenton effluent by a fungal consortium without pre-neutralization upon base addition: Microbial screening and performance

Great progresses have been made to carry out Fenton oxidation under neutral or alkaline pH in which, nevertheless, organic acids and other acidic intermediates usually result in acidic Fenton effluent. To eliminate the classical neutralization step prior to biological treatment, acid-tolerant microbes were here screened and used for purification of acidic Fenton effluent to achieve pH increase and further COD (chemical oxygen demand) removal. The bacterial and fungal community diversity was analyzed before and after screening for acid-tolerant microbes. After screening the bacterial diversity sharply decreased while the fungal diversity at the genus level became richer, mainly including Phialemoniopsis (relative abundance 38.69%), Vanrija (20.08%), Hypocreaceae (18.44%) and Candida (14.74%). Acidic pH and residual H2O2 are the features of Fenton effluent; hence, effects of pH and H2O2 on the screened acid-tolerant microbes were investigated in the aspects of growth rate and oxygen uptake rate. The kinetic parameters, including YH–biomass yield coefficient; Kd–biomass decay coefficient; μm–specific maximum COD removal rate; Ks–half saturation constant for COD removal, of the acid-tolerant microbes using 1/5 YM (yeast extract and malt extract culture medium) as substrate at 25 °C were measured by respirometric methodology. In BAC (biological activated carbon) inoculated with acid-tolerant microbes to treat actual Fenton effluent, the average COD removal efficiency was 72% at HRT (hydraulic retention time) of 3 h and the effluent pH was above 6 after removing the dissolved CO2 by air stripping. This study will provide a basis for developing a new combined process including Fenton and biological oxidation without pH adjustment.

Nutrient Export with Logs, and Release from Residues, after Harvest of a <i>Pinus taeda</i> Plantation in Uruguay

In Uruguay, Pinus taeda is usually planted a few months after harvest of the former turn, therefore; decomposing residues represents a nutrient source for the new plantation. The aim of this study was to determine the biomass and nutrient extraction off site, following the harvest of a P. taeda plantation. Residue decomposition patterns, and nutrient release were also examined. The site will be referred as S1, corresponding to the clear cut of a 22-year-old P. taeda plantation. Before the clear cut 10 trees were harvested, and logs, branches, twigs, and needles separately weighed. Additionally, forest litter at harvest time was quantified in three different areas. To assess decomposition, mesh bags with residues were allocated in three areas over the forest litter, and samples were taken periodically for 26 months. The remaining biomass, N, P K, Ca, and Mg contents were determined in the different fractions, calculating decompositon rates. Most of the harvested biomass was removed in logs, but the proportion of nutrients exported was considerably lower. Needles showed the highest biomass loss and only 39.1% remained after 26 months, while branches presented high rates in the first two months after cut, but slower thereafter, and at the end of the study more than two thirds of the woody residues remained. Potassium was rapidly released from the residues, while Ca, and Mg, were slowly released, and there was evidence of N and P immobilization in the early stages of decomposition. It was concluded that, although a lower proportion of nutrients were exported, compared to biomass, in the long term, nutrient export with logs could be significant for the sustainability of this production system. While K release from residues did not depend on biomass decay, the slow decomposition, and release of the other nutrients, indicates that this process could have been delayed by nutrient scarcity.

Modularity of insect production and processing as a path to efficient and sustainable food waste treatment

Currently up to half of all food produced is wasted. The food waste is treated with commonly used methods. Due to emissions associated with biomass decay and extensive transportation and storage necessities, this entails a negative effect on the environment. Modular systems of food waste treatment, applicable for a range of instances along the food supply chain might be a potential solution. By evaluating economic and environmental aspects, this study focuses on the configuration and assessment of solutions based on insects specifically for the conditions in Germany. Insects are selected because of their ability to convert low value food waste into biomass (rich in proteins and fats) and frass which can be sold for other purposes. Tenebrio molitor and Hermetia illucens are fed on side streams composed of brewery grains, potato peels or expired food from retail. For T. molitor, no life cycle assessment (LCA) is performed, as this species did not fulfil the design requirements of the modular system. For H. illucens the results of the economic analysis and LCA show that the system performance depends on the type of waste. The environmental and economic efficiency of H. illucens feeding on brewery grains or expired food is higher than the one of incineration and anaerobic digestion. Compared to composting, H. illucens is environmentally more efficient and economically comparable to the operating costs of composting. If potato peels are considered as feed for insects, the commonly used waste treatment methods show better results in all aspects.

Ulva prolifera green-tide outbreaks and their environmental impact in the Yellow Sea, China.

The Ulva prolifera green tides in the Yellow Sea, China, which have been occurring since 2007, are a serious environmental problem attracting worldwide attention. Despite extensive research, the outbreak mechanisms have not been fully understood. Comprehensive analysis of anthropogenic and natural biotic and abiotic factors reveals that human activities, regional physicochemical conditions and algal physiological characteristics as well as ocean warming and biological interactions (with microorganism or other macroalgae) are closely related to the occurrence of green tides. Dynamics of these factors and their interactions could explain why green tides suddenly occurred in 2007 and decreased abruptly in 2017. Moreover, the consequence of green tides is serious. The decay of macroalgal biomass could result in hypoxia and acidification, possibly induce red tide and even have a long-lasting impact on coastal carbon cycles and the ecosystem. Accordingly, corresponding countermeasures have been proposed in our study for future reference in ecosystem management strategies and sustainable development policy.

Sources of anammox granular sludge and their sustainability in treating low-strength wastewater

Anaerobic ammonium oxidation (anammox) has been widely applied in the treatment of high-strength nitrogen wastewaters. However, few engineering practices were reported to treat low-strength nitrogen wastewaters. In this study, three types of anammox granular sludge (GS) were separately collected from the expanded granular sludge bed (EGSB) reactors treating nitrogen wastewaters at high (H-), moderate (M-) and low (L-) nitrogen loading rates (NLRs), and employed for the treatment of low-strength nitrogen wastewater in sequencing batch advanced nitrogen removal (ANR) systems. The ANR system with M-GS (namely M-ANR system) was most useful. At the initial biomass concentration of 2.43 g-VSS·L−1, cycle length of 8 h and influent total nitrogen (TN) concentration of less than 15 mg·L−1, the performance data were as follows: effluent TN of less than 1 mg·L−1, TN removal efficiency of more than 92.8%, the nitrogen removal rate (NRR) of 0.039 kg-N·m−3·d−1. The efficient performance lasted as long as 46 cycles, indicating the sustainability of the M-ANR system. The advanced microscopic analysis and metagenomic analysis were applied to reveal the successful but non-permanent treatment by the M-ANR system. The long-time lag between biomass decay and sludge activity decay provided a window period for the good performance of M-ANR system. However, the weak support of oligotrophic habitat for anaerobic ammonium oxidizing bacteria community was doomed to the degradation of anammox GS, resulting in gradual loss of their activities. A periodic addition of fresh M-GS or a periodic rejuvenation cultivation in the eutrophic habitat is necessary to achieve a permanent performance.

Intensive membrane cleaning for MBRs equipped with flat-sheet ceramic membranes: Controlling negative effects of chemical reagents used for membrane cleaning

Intensive membrane cleaning can be used with ceramic membranes since they are physically/chemically robust. It might therefore be possible for membrane bioreactors (MBRs) to be operated under the condition of a high membrane flux when ceramic membranes are used with such intensive membrane cleaning. In this study, bench-scale MBRs equipped with flat-sheet ceramic membranes were operated for long periods. Circulation of granular materials (cylindrical polyurethane) in the tank and frequent chemically enhanced backwash (CEB) were used as intensive physical cleaning and chemical cleaning in this study, respectively. Experiments were carried out with synthetic wastewater. The use of granular materials, which can cause significant damage to polymeric membranes (Kurita et al., 2015), was effective for controlling the formation of cake (deposition of microbial flocs) on the surface of the ceramic membranes. When both mechanical cleaning using the granular materials and CEB with 1000 ppm of sodium hypochlorite (NaClO) were applied, contrary to an expectation, evolution of reversible fouling (formation of a transparent gel layer on the membrane surface) became uncontrollable, whereas irreversible fouling was effectively controlled. The use of NaClO induced release of organic macromolecules via biomass decay, leading to the evolution of reversible fouling. When the intensity of CEB with NaClO was adequately lowered, with the aid of the mechanical cleaning using the granules, the bench-scale MBR could be operated stably under an elevated membrane flux for a long period (>70 days). It was postulated that the adjustment of CEB intensity preferably altered properties of organic macromolecules released from biomass: the structure of the gel layer was porous when the CEB intensity was lowered. When CEB is used in MBRs, it is thus important to balance cleaning efficiency and its harmful effect on biomass. When adequate CEB is used with intensive mechanical cleaning, MBRs with ceramic membranes can be operated under high flux conditions.

Disentangling limnological processes in the time‐frequency domain

AbstractState variables in lake ecosystems are subject to processes that act on different time scales. The relative importance of each of these processes changes over time, e.g., due to varying constraints of physical, biological, and biogeochemical processes. Correspondingly, continuous automatic measurements at high temporal resolution often reveal intriguing patterns that can rarely be directly ascribed to single processes. In light of the rather complex interplay of such processes, disentangling them requires more powerful methods than researchers have applied up to this point. For this reason, we tested the potential of wavelet coherence, based on the assumption that different processes result in correlations between different variables, on different time scales and during different time windows across the seasons. The approach was tested on a set of multivariate hourly data measured between the onset of an ice cover and a cyanobacterial summer bloom in the year 2009 in the Müggelsee, a polymictic eutrophic lake. We found that processes such as photosynthesis and respiration, the growth and decay of phytoplankton biomass, dynamics in the CO2‐carbonate system, wind‐induced resuspension of particles, and vertical mixing all occasionally served as dominant drivers of the variability in our data. We therefore conclude that high‐resolution data and a method capable of analyzing time series in both the time and the frequency domain can help to enhance our understanding of the time scales and processes responsible for the high variability in driver variables and response variables, which in turn can lay the ground for mechanistic analyses.

Chemical-Free Recovery of Elemental Selenium from Selenate-Contaminated Water by a System Combining a Biological Reactor, a Bacterium-Nanoparticle Separator, and a Tangential Flow Filter.

Biological selenate (SeO42-) reduction to elemental selenium nanoparticles (SeNPs) has been intensively studied but little practiced because of the additional cost associated with separation of SeNPs from water. Recovery of the SeNPs as a valuable resource has been researched to make the approach more competitive. Separation of the intracellular SeNPs from the biomass usually requires the addition of chemicals. In this research, a novel approach that combined a biological reactor, a bacterium-SeNP separator, and a tangential flow ultrafiltration module (TFU) was investigated to biologically reduce selenate and separate the SeNPs, biomass, and water from each other. This approach efficiently removed and recovered selenium while eliminating the use of chemicals for separation. The three units in the approach worked in synergism to achieve the separation and recovery. The TFU module retained the biomass in the system, which increased the biomass retention time and allowed for more biomass decay through which intracellular SeNPs could be released and recovered. SeNP aggregates were separated from bacterial aggregates due to their different interactions with a tilted polyethylene sheet in the bacterium-SeNP separator. SeNP aggregates stayed on the polyethylene sheet while bacterial aggregates settled down to the bottom of the separator.

Nitrogen release and its influence on anammox bacteria during the decay of Potamogeton crispus with different values of initial debris biomass

Aquatic macrophytes play a significant role in the nutrient cycle of freshwater ecosystems. However, nutrients from plant debris release into both sediments and overlying water if not timely harvested. To date, minimal information is available regarding nutrient release and its subsequent influences on bacterial communities with decaying debris. In this study, Potamogeton crispus was used as a model plant. Debris biomass levels of 0 g (control, J-CK), 10 g dry weight (DW) (100 g DW/m2, J-10 g), 40 g DW (400 g DW/m2, J-40 g) and 80 g DW (800 g DW/m2, J-80 g) were used to simulate the different biomass densities of P. crispus in field. The physicochemical parameters of overlying water and sediment samples were analysed. The community composition of anammox bacteria in the sediment was also analysed using 16S rRNA genes as markers. The results showed that dissolved oxygen and pH dramatically decreased, whereas total nitrogen (TN) and NH4+-N concentrations increased in the overlying water in the initial stage of P. crispus decomposition. However, NO3−-N concentration changes in the overlying water were more complicated. The concentrations of organic matter, TN and NH4+-N in the sediment all increased, but the rate of increase varied among the groups with different initial biomass levels, indicating that these physicochemical properties in sediment are significantly affected by debris biomass level and decay time. In addition, the order of anammox bacteria abundance was J-40 g > J-CK > J-80 g > J-10 g. Moreover, the community structure of anammox bacteria were simpler compared to that of J-CK as debris biomass level increased. The results demonstrate that P. crispus debris decomposition could affect the ecological distribution of anammox bacteria. Such influence clearly varies with varying amounts of P. crispus biomass debris. This information could be useful for the management of aquatic macrophytes in freshwater ecosystems.

Long-term time series of annual ecosystem production (1985–2010) derived from tree rings in Douglas-fir stands on Vancouver Island, Canada using a hybrid biometric-modelling approach

We used a hybrid-biometric modelling approach that combines tree-ring based stand reconstruction and the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to estimate past magnitude and inter-annual variation of net primary production (NPP), net ecosystem production (NEP), and heterotrophic respiration (Rh) in plots located within the footprint of an eddy-covariance (EC) installation in a Douglas-fir stand of 1949 origin (DF49 or AmeriFlux CA-Ca1). Stand reconstruction estimated NEP showed excellent correspondence with EC-estimated NEP over the period 1998–2010 (r2 = 0.79, mean difference 24 gC m−2 year−1). Estimates of carbon use efficiency, aboveground NPP, and post-disturbance C dynamics following the harvest of DF49 in 2011 showed discrepancies between modelled estimates and independent data, which were attributed to underestimates of coarse litterfall in previous field studies and to uncertainty in the production, turnover, and post-mortality decay of non merchantable woody biomass in the CBM-CFS3. Despite these issues, the results provide further evidence of the potential use of tree-ring data to expand the availability of long-term estimates of annual ecosystem production and their ability to increase our understanding of forest C dynamics.

A Mesocosm Double Feature: Insights into the Chemical Makeup of Marine Ice Nucleating Particles

AbstractThe abundance of atmospheric ice nucleating particles (INPs) is a source of uncertainty for numerical representation of ice-phase transitions in mixed-phase clouds. While sea spray aerosol (SSA) exhibits less ice nucleating (IN) ability than terrestrial aerosol, marine INP emissions are linked to oceanic biological activity and are potentially an important source of INPs over remote oceans. Inadequate knowledge of marine INP identity limits the ability to parameterize this complex INP source. A previous manuscript described abundances of marine INPs in relation to several aerosol composition and ocean biology observations during two laboratory mesocosm experiments. In this study, the abundances and chemical and physical properties of INPs found during the same mesocosm experiments were directly probed in SSA, seawater, and surface microlayer samples. Two unique marine INP populations were found: 1) dissolved organic carbon INPs are suggested to be composed of IN-active molecules, and 2) particulate organic carbon INPs are attributed as intact cells or IN-active microbe fragments. Both marine INP types are likely to be emitted into SSA following decay of phytoplankton biomass when 1) the surface microlayer is significantly enriched with exudates and cellular detritus and SSA particles are preferentially coated with IN-active molecules or 2) diatom fragments and bacteria are relatively abundant in seawater and therefore more likely transferred into SSA. These findings inform future efforts for incorporating marine INP emissions into numerical models and motivate future studies to quantify specific marine molecules and isolate phytoplankton, bacteria, and other species that contribute to these marine INP types.

Mixed evolutionary origins of endogenous biomass-depolymerizing enzymes in animals

BackgroundAnimals are thought to achieve lignocellulose digestion via symbiotic associations with gut microbes; this view leads to significant focus on bacteria and fungi for lignocellulolytic systems. The presence of biomass conversion systems hardwired into animal genomes has not yet been unequivocally demonstrated.ResultsWe perform an exhaustive search for glycoside hydrolase (GH) genes from 21 genomes representing major bilaterian (Ecdysozoa, Spiralia, Echinodermata and Chordata) and basal metazoan (Porifera and Cnidaria) lineages. We also assessed the genome of a unicellular relative of Metazoa, Capsaspora owczarzaki and together with comparative analyses on 126 crustacean transcriptomes, we found that animals are living bioreactors at a microscale as they encode enzymatic suites for biomass decomposition. We identified a total of 16,723 GH homologs (2373 genes from animal genomes and 14,350 genes from crustacean transcriptomes) that are further classified into 60 GH families. Strikingly, through phylogenetic analyses, we observed that animal lignocellulosic enzymes have multiple origins, either inherited vertically over millions of years from a common ancestor or acquired more recently from non-animal organisms.ConclusionWe have conducted a systematic and comprehensive survey of GH genes across major animal lineages. The ability of biomass decay appears to be determined by animals’ dietary strategies. Detritivores have genes that accomplish broad enzymatic functions while the number of GH families is reduced in animals that have evolved specialized diets. Animal GH candidates identified in this study will not only facilitate future functional genomics research but also provide an analysis platform to identify enzyme candidates with industrial potential.

Microbial diversity of thermophiles with biomass deconstruction potential in a foliage-rich hot spring.

The ability of thermophilic microorganisms and their enzymes to decompose biomass have attracted attention due to their quick reaction time, thermostability, and decreased risk of contamination. Exploitation of efficient thermostable glycoside hydrolases (GHs) could accelerate the industrialization of biofuels and biochemicals. However, the full spectrum of thermophiles and their enzymes that are important for biomass degradation at high temperatures have not yet been thoroughly studied. We examined a Malaysian Y‐shaped Sungai Klah hot spring located within a wooded area. The fallen foliage that formed a thick layer of biomass bed under the heated water of the Y‐shaped Sungai Klah hot spring was an ideal environment for the discovery and analysis of microbial biomass decay communities. We sequenced the hypervariable regions of bacterial and archaeal 16S rRNA genes using total community DNA extracted from the hot spring. Data suggested that 25 phyla, 58 classes, 110 orders, 171 families, and 328 genera inhabited this hot spring. Among the detected genera, members of Acidimicrobium, Aeropyrum, Caldilinea, Caldisphaera, Chloracidobacterium, Chloroflexus, Desulfurobacterium, Fervidobacterium, Geobacillus, Meiothermus, Melioribacter, Methanothermococcus, Methanotorris, Roseiflexus, Thermoanaerobacter, Thermoanaerobacterium, Thermoanaerobaculum, and Thermosipho were the main thermophiles containing various GHs that play an important role in cellulose and hemicellulose breakdown. Collectively, the results suggest that the microbial community in this hot spring represents a good source for isolating efficient biomass degrading thermophiles and thermozymes.

Characterization Composition of Soluble Microbial Products in an Aerobic Granular Sludge System

Using flocculent activated sludge as seed sludge to cultivate aerobic granular sludge in a SBR, the main objective of this study was focused on the accumulation, relative molecular mass distribution, and composition of soluble microbial products (SMP) in an aerobic granular sludge (AGS) system. SMP were predominant (71-85 mg·L-1) in the effluent of the AGS system. The formation of SMP was related to substrate utilization, biomass decay, and EPS hydrolysis. A relative molecular mass distribution analysis indicated that the majority of SMP, accounting for about 54.8%-71.7%, had Mr<3×103; whereas, the Mr>100×103 formed a small fraction, constituting only 9.3%-14.5%. Three-dimensional excitation emission matrix fluorescence spectra (3D-EEM) identified four peaks in SMP, belonging to aromatic protein-like, tryptophan protein-like, humic acid-like, and fulvic acid-like substances. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that esters (39.0%), short chain alkanes (14.9%), alkenes (11.7%), and alcohols (7.6%) were the main compounds in SMP. Most notably, bis(2-ethylhexyl) phthalate, as one kind of ester, accounted for 32% of the identified SMP.

Biological Limitations of Dechlorination of cis-Dichloroethene during Transport in Porous Media.

We applied a mathematical model to data from experimental column studies to understand the dynamics of successful and unsuccessful reductive dechlorination of chlorinated ethenes in groundwater under different flow conditions. In laboratory column experiments (reported previously), it was observed that complete dechlorination of cis-dichloroethene to ethene was sustained at high flow velocity (0.51 m/d), but that dechlorination failed at medium or low flow velocity (0.080 or 0.036 m/d). The mathematical model applied here accounts for transport of chlorinated ethenes in flowing groundwater, mass transfer of chlorinated ethenes between mobile groundwater and stationary biofilms, and diffusion and biodegradation within the biofilms. Monod kinetics with competitive inhibition are used to describe biodegradation. Nearly all parameters needed to solve the model are estimated independently from batch and nonreactive transport experiments. Comparing the model predictions to the experimental results permits the evaluation of three hypothesized biological limitations: insufficient supply of electron donor, decay of dechlorinators' biomass, and reduction in bacterial metabolism rates. Any of these three limitations are able to adequately describe observed experimental data, but insufficient supply of electron donor is the most plausible explanation for failure of dechlorination. Therefore, an important conclusion of this investigation is that insufficient hydrogen production occurs if groundwater flow is too slow to provide adequate flux of electron donor. Model simulations were in good agreement with experimental results for both successful and unsuccessful dechlorination, suggesting the model is a valid tool for describing transport and reductive dechlorination. An implication of our findings is that in engineered or natural bioremediation of chloroethene-contaminated groundwater, not only must the proper dechlorinating organisms be present, but also proper groundwater flow conditions must be maintained or else dechlorination may fail.

Lipid biomarker signatures as tracers for harmful cyanobacterial blooms in the Baltic Sea.

The recent proliferation of harmful cyanobacterial blooms (cyanoHABs) in the Baltic and other marginal seas poses a severe threat for the health of infested ecosystems as e.g. the massive export and decay of cyanobacterial biomass facilitates the spread of bottom water hypoxia. There is evidence that cyanoHABs occurred repeatedly in the Baltic Sea but knowledge of their spatiotemporal distribution and the cyanobacteria that contributed to them is limited. In this study, we examined representatives of the major bloom-forming heterocystous cyanobacteria (i.e. Aphanizomenon, Dolichospermum (formerly Anabaena) and Nodularia) to establish lipid fingerprints that allow tracking these environmentally important diazotrophs in the modern and past Baltic Sea. The distribution of normal and mid-chain branched alkanes, fatty acid methyl esters, bacteriohopanepolyols and heterocyst glycolipids permitted a clear chemotaxonomic separation of the different heterocystous cyanobacteria but also indicated a close phylogenetic relationship between representatives of the genera Aphanizomenon and Dolichospermum. Compared to the discontinuous nature of phytoplankton surveys studies, the distinct lipid profiles reported here will allow obtaining detailed spatiotemporal information on the frequency and intensity of Baltic Sea cyanoHABs as well as their community composition using the time-integrated biomarker signatures recorded in surface and subsurface sediments. As heterocystous cyanobacteria of the genera Aphanizomenon, Dolichospermum and Nodularia are generally known to form massive blooms in many brackish as well as lacustrine systems worldwide, the chemotaxonomic markers introduced in this study may allow investigating cyanoHABs in a great variety of contemporary environments from polar to tropical latitudes.

Anomalous mercury enrichment in Early Cambrian black shales of South China: Mercury isotopes indicate a seawater source

Extremely elevated Hg levels up to the μgg−1 range were found in sulfide-rich black shale and phosphorite in the lowermost part of the Early Cambrian black shale sequences on the Yangtze Platform in South China. In this study, mercury isotopes were used to help resolve the origin of this anomalous Hg enrichment. Mass independent fractionation signatures of Hg isotopes with positive Δ199Hg values of 0.13 to 0.24‰ and positive Δ200Hg values of 0.05 to 0.10‰ were observed, indicating seawater is an important source of Hg. We hypothesize that upwelling of nutrient-rich waters from the open ocean resulted in high bioproductivity in the photic zone with concomitant scavenging of Hg from seawater. Advanced decay of biomass and remineralization under anoxic to euxinic conditions combined with very low clastic input led to enrichment of Hg and a broad spectrum of other redox-sensitive and biogenic metals up to 107 compared to modern seawater. Such spectacular hydrogenous metal enrichment has previously been observed in the oxic deep-sea environment only, i.e. manganese crusts/nodules.

Comparative analysis of basidiomycete transcriptomes reveals a core set of expressed genes encoding plant biomass degrading enzymes

Basidiomycete fungi can degrade a wide range of plant biomass, including living and dead trees, forest litter, crops, and plant matter in soils. Understanding the process of plant biomass decay by basidiomycetes could facilitate their application in various industrial sectors such as food & feed, detergents and biofuels, and also provide new insights into their essential biological role in the global carbon cycle. The fast expansion of basidiomycete genomic and functional genomics data (e.g. transcriptomics, proteomics) has facilitated exploration of key genes and regulatory mechanisms of plant biomass degradation. In this study, we comparatively analyzed 22 transcriptome datasets from basidiomycetes related to plant biomass degradation, and identified 328 commonly induced genes and 318 repressed genes, and defined a core set of carbohydrate active enzymes (CAZymes), which was shared by most of the basidiomycete species. High conservation of these CAZymes in genomes and similar regulation pattern in transcriptomics data from lignocellulosic substrates indicate their key role in plant biomass degradation and need for their further biochemical investigation.

Comparative assessment of the environmental impacts of nuclear, wind and hydro-electric power plants in Ontario: A life cycle assessment

In this study, we analyze, assess and compare the environmental impacts of nuclear, wind and hydro power generation in the province of Ontario, Canada through a comprehensive life cycle assessment approach. The upstream, downstream and operation phases during the life cycle of these power generation methods are included. The output emissions inventoried in the study are carbon dioxide, methane, sulphur oxides, nitrogen oxides and total particulate matter. The CML 2001 impact assessment methodology is utilized for impact assessment. The environmental impacts included are global warming potential, acidification potential, eutrophication potential, photochemical ozone creation potential and human toxicity potential. Hydro reservoir facilities with bio mass decay are found to have a life cycle GWP100 of 15.2 g CO2-eq/kWh, which is comparatively higher than wind (12.05 g CO2-eq/kWh) and nuclear power life cycles (3.402 g CO2-eq/kWh). However, hydropower is found to have substantially low impacts when other environmental impact categories, such as acidification potential, eutrophication potential, photochemical ozone creation potential and human toxicity potential are considered. This indicates only greenhouse gas emissions are not sufficient to describe the environmental performance of any product system. Wind power life cycle contributed most significantly to acidification, eutrophication, photochemical ozone creation and human toxicity potentials. This is mainly attributed to the construction phase of the life cycle. Hence, development of more environmentally benign wind turbine construction methods is suggested. For the nuclear power scenario, both upstream and decommissioning phases are identified as major contributors to environmental impacts.