Decomposition Research Articles

Treatment of shrimp pond bottom sludge in Binh Dai district, Ben Tre province towards reuse as raw materials for organic fertilizer production

In this study, bottom sludge was collected from intensive shrimp ponds and aquaculture areas in Ben Tre province. The characteristics of the sludge sample taken to have a clay-meat texture, low organic matter, nitrogen, and total phosphorus content. Sludge from intensive shrimp ponds has very high salinity and solicitation (45-78%), useful nitrogen and useful phosphorus are quite rich, and heavy metal content as in shrimp pond sludge is low, below the threshold of contaminated soil. Polluted pollutants are recovered and treated in the direction of reuse as a source of raw materials for the production of organic fertilizers by aerobic decomposition using rice straw as a filler and incubated for 52 days. The results showed that the properties of the shrimp pond bottom sludge, which changed significantly during the composting process and contained nutritional elements, reached the required concentrations for organic fertilizers applied in Agriculture. After an incubation period of 52 days, the pH varied between 6.95 and 7.04. Humidity ranges from 52.1% to 68.3%. The temperature during composting fluctuates sharply: from 21.50C to 43.40C. Salinity decreased from 15.24 ppm to 12.36 ppm. The C/N ratio in the initial sludge sample was 8.64 and after incubation, it decreased to 6.4 (experiment 1 TN1); 7.6 (experiment 2 - TN2). After 52 days of incubation, the compost from shrimp pond bottom sludge had an organic composition of 15.6%, total nitrogen was 2.2%, and total phosphorus was 1.8%.

Effect of relative water content in rice genotypes after gypsum and bio-compost amended sodic soil

Sodic soils have immense productivity potential, if managed through proper technology interventions. Biocompost is prepared by composting pressmud (a sugar industry byproduct) received from cane juice filtration and spent wash received from distilleries through microbial aerobic decomposition and gypsum received from waste material of mining can be used to reclaim sodic soils. Field experiments were conducted during the kharif season of 2018 and 2019 at the ICAR-Indian Agricultural Research Institute, Sub Regional Station, Pusa (Samastipur). The promising results revealed that the mean of leaf relative water content at pre-flowering stage in the salt-tolerant genotypes ranged between 69.47 to 82.20 per cent during 2018 and 69.52 to 82.24 per cent during 2019. The mean of leaf relative water content at grain filling stage in all the genotypes varied between 77.55 to 85.45 per cent during 2018 and 75.49 to 85.16 per cent during 2019. Soil amendments and genotypes interaction were found significant in both the years at grain filling stage.

Phonetic Segmentation using a Wavelet-based Speech Cepstral Features and Sparse Representation Classifier

Speech segmentation is the process of dividing speech signal into distinct acoustic blocks that could be words, syllables or phonemes. Phonetic segmentation is about finding the exact boundaries for the different phonemes that composes a specific speech signal. This problem is crucial for many applications, i.e. automatic speech recognition (ASR). In this paper we propose a new model-based text independent phonetic segmentation method based on wavelet packet speech parametrization features and using the sparse representation classifier (SRC). Experiments were performed on two datasets, the first is an English one derived from TIMIT corpus, while the second is an Arabic one derived from the Arabic speech corpus. Results showed that the proposed wavelet packet de composition features outperform the MFCC features in speech segmentation task, in terms of both F1-score and R-measure on both datasets. Results also indicate that the SRC gives higher hit rate than the famous k-Nearest Neighbors (k-NN) classifier on TIMIT dataset.

Characterizing ecosystem-driven chemical composition differences in natural and drained Finnish bogs using pyrolysis-GC/MS

Aerobic decomposition increases in drained peatlands; releasing stored organic matter (OM) and shifting greenhouse gas fluxes from sink to source. This study explored how drainage influenced peat OM chemical composition by investigating paired sites from a Sphagnum-dominated ombrotrophic Finnish bog undergoing contrasting hydrological management (natural and drained). Peat OM was investigated in replicate cores using analytical pyrolysis, compared with observed vegetation, elemental analysis (O:C, N:C), stable isotopes (δ13C, δ15N), and fraction radiocarbon. Principal component analysis of quantified pyrolysis products separated four primary components: vascular plants vs Sphagnum, aerobic degradation of fresh plant biomass, anaerobic processes in water-saturated depths, and pine vs Eriophorum. The largest influence of drainage on peat chemistry was via aerobic decomposition (decreased abundance of Sphagnum phenols and simple polysaccharides; accumulation of macromolecular polysaccharides) (p < 0.05, 0–2 cm). Drainage-induced shifts in vegetation (from Sphagnum to Pinus sylvestris (p < 0.01, 0–2 cm) were reflected by increased abundance in lignin, N-compounds, and lipids, and decreased abundance in phenols and polysaccharides. Anaerobic processes also differentiated the natural and drained sites and primarily affected polysaccharides (p < 0.05, 0–2, 8–10 cm). Vegetation shifts and aerobic decomposition similarly affected many of the same compounds upon drainage– demonstrating the simultaneous influence of different processes on the same OM. Pre-drainage inter-core variation illustrated the importance of replicate cores in disentangling anthropogenic changes from natural biodiversity. These findings suggest that even short-term and moderate alterations in peatland hydrology strongly influence the chemical composition of peat OM, and that its chemistry serves as an effective indicator to assess decomposition status.

Degradation activity of fungal communities on avocado peel (Persea americana Mill.) in a solid-state process: mycobiota successions and trophic guild shifts.

To explore the capability of soil mycobiota to degrade avocado peel waste and identify relevant successions and trophic guild shifts, fungal communities from three environments with different land uses were evaluated in a solid-state process. Soil samples used as inoculum were collected from a pristine mature tropical forest, a traditionally managed Mayan land, and an intensively managed monospecific avocado plantation. Soil-substrate mixes were evaluated for 52weeks to evaluate organic matter decay and the carbon-to-nitrogen ratio. Amplicon-based high-throughput sequencing from internally transcribed spacer (ITS) analysis revealed significant differences in fungal communities widely dominated by Fusarium sp. and Clonostachys sp.; however, less represented taxa showed relevant shifts concomitantly with organic matter content drops. Trophic guild assignment revealed different behaviors in fungal communities between treatments over the 52weeks, suggesting distinct preconditioning of fungal communities in these environments. Overall, the results lead to the identification of promising degradation moments and inoculum sources for further consortia enrichment or bioprospecting efforts.

Microbial community dynamics in the mesophilic and thermophilic phases of textile waste composting identified through next-generation sequencing

Composting is a promising source of mesophilic and thermophilic microorganisms directly involved in the decay of organic matter. However, there is a paucity of information related to bacterial and fungal diversity in compost and their enzymatic activities during the composting process. In this work, bacterial and fungal diversity during the mesophilic and thermophilic phases of textile waste composting was investigated as a way to explain the physical–chemical results obtained during the composting process. This was accomplished using a next-generation sequencing approach that targets either the 16S rRNA or ITS genomic regions of bacteria and fungi, respectively. It was observed that Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant bacterial phyla present at the mesophilic phase but not at the thermophilic one. Composting textile waste exhibits a sustained thermophilic profile (above 55 °C) that usually precludes fungal activity. Nonetheless, the presence of fungi at the thermophilic phase was observed. Rozellomycota, Basidiomycota, and Ascomycota were the most dominant phyla during both composting phases. Such thermophilic fungi with great ability to decay organic matter could be isolated as pure cultures and used for the bioaugmentation of textile waste composting to achieve an advanced maturity level of textile waste compost.

Comparative soft-tissue preservation in Holocene-age capelin concretions.

Determining how soft tissues are preserved and persist through geologic time are continuing challenge because decay begins immediately after senescence while diagenetic transformations generally progress over days to millions of years. However, in recent years, carbonate concretions containing partially-to-fully decayed macroorganisms have proven to be remarkable windows into the diagenetic continuum revealing insights into the fossilization process. This is because most concretions are the result of biologically induced mineral precipitation caused by the localized decay of organic matter, which oftentimes preserves a greater biological signal relative to their host sediment. Here we present a comparative lipid biomarker study investigating processes associated with soft-tissue preservation within Holocene-age carbonate concretions that have encapsulated modern capelin (Mallotus villosus). We focus on samples collected from two depositional settings that have produced highly contrasting preservation end-members: (1) Kangerlussuaq, Greenland: a marine environment, which, due to isostatic rebound, has exposed strata containing concretions exhibiting exceptional soft-tissue preservation (6-7kya), and (2) Greens Creek, Ottawa, Canada: a paleo brackish-to-freshwater marine excursion containing concretions exhibiting skeletal remains (~11kya). Lipid biomarker analysis reveals endogenous capelin tissues and productive waters at Kangerlussuaq that are in sharp contrast to Greens Creek concretions, which lack appreciable capelin and environmental signals. Comparable distributions of bacterial fatty acids and statistical analyses suggest soft-tissue preservation within concretions is agnostic to specific heterotrophic decay communities. We, therefore, interpret preservation within carbonate concretions may represent a race between microbially induced authigenic precipitation and decay. Namely, factors resulting in exceptional preservation within concretions likely include: (1) organic matter input, (2) rate of decay, (3) carbonate saturation, (4) porewater velocity, and (5) rate of authigenic (carbonate) precipitation resulting in arrested decay/bacterial respiration due to cementing pore spaces limiting the diffusion of electron acceptors into the decay foci.

Spatio-temporal variations of cave-air CO2 concentrations in two Croatian show caves: Natural vs. anthropogenic controls

Carbon dioxide (CO2) concentration (CDC) plays an important role in karst processes, governing both carbonate deposition and dissolution, affecting not only natural processes, but also human activities in caves adapted for tourism. Its variations due to various controlling parameters was observed from 2017 to 2021 in two Croatian show caves (Manita peć and Modrič) where we examined inter- and within-cave correlation of internal aerology regarding the sources, sinks and transport mechanism of CDC in a karst conduit setting. In both caves, the main sources of CO2 are: i) plant and microbial activity i.e. root respiration and organic matter decay within soil horizons and fractured epikarst, and ii) degassing from CO2-rich percolation water. The main sink of CO2 is dilution with outside air due to cave ventilation. Chimney-effect driven ventilation controlled by seasonal differences between surface and cave air temperatures shows winter (Tout&lt;Tcave) and summer (Tout&gt;Tcave ) ventilation regime, which are modulated by the geometry of cave passages, the transmissivity of the overlying epikarst, and occasionally by the external winds, especially the gusty north-eastern bora wind. In these terms, the Modrič Cave appears to be more confined and less ventilated, with a substantial CDC difference between the left (550-7200 ppm) and right (1475- &gt;10,000 ppm) passages. The Manita peć Cave is, in contrast, ventilated almost year-round, having 7 months of CDC equilibrated with the outside atmosphere and the highest summer CDC values of ~1410 ppm. In both caves, at the current level of tourist use, anthropogenic CO2 flux is not a matter of concern for cave conservation. In turn, in the innermost part of the right Modrič Cave passage visitors’ health might be compromised, but the tourists are allowed only in the left passage. Speleothem growth rate, recognized as a useful palaeoenvironmental proxy for speleothem-based palaeoclimate studies, strongly depends on CDC variations, so the high CDCs recorded in the Modrič Cave indicate the potential periods with no speleothem deposition due to the hampered degassing of CO2 from the dripping groundwater. The opposite effect i.e. enhanced ventilation (that supports calcite precipitation) during the windy glacials/stadials, as well as substantial vegetational changes must also be taken into consideration when interpreting environmental records from spelean calcite.

Revaluating forest drought experiments according to future precipitation patterns, ecosystem carbon and decomposition rate responses: A meta-analysis.

Moisture availability is a strong determinant of decomposition rates in forests worldwide. Climate models suggest that many terrestrial ecosystems are at risk from future droughts, suggesting moisture limiting conditions will develop across a range of forests worldwide. The impacts of increasing drought conditions on forest carbon (C) fluxes due to shifts in organic matter decay rates may be poorly characterised due to limited experimental research. To appraise this question, we conducted a meta-analysis of forest drought experiment studies worldwide, examining spatial limits, knowledge gaps and potential biases. To identify limits to experimental knowledge, we projected the global distribution of forest drought experiments against spatially modelled estimates of (i) future precipitation change, (ii) ecosystem total above-ground C and (iii) soil C storage. Our assessment, involving 115 individual experimental study locations, found a mismatch between the distribution of forest drought experiments and regions with higher levels of future drought risk and C storage, such as Central America, Amazonia, the Atlantic Forest of Brazil, equatorial Africa and Indonesia. Decomposition rate responses in litter and soil were also relatively under-studied, with only 30 experiments specifically examining the potential experimental impacts of drought on C fluxes from soil or litter. We propose new approaches for engaging experimentally with forest drought research, utilising standardised protocols to appraise the impacts of drought on the C cycle, while targeting the most vulnerable and relevant forests.

Biomineralization of primary carbonate cements: a new biosignature in the fossil record from the Anisian of Southern Italy

Biomineralization is a generic term used to indicate biological-mediated mineral formation. In carbonate mineralization, nucleation of crystals can be: (1) controlled directly by the organisms, like in the skeletal formation of most metazoans; (2) induced by microbial communities, by indirect precipitation mediated by their metabolic activities; or (3) influenced by organic matter decay, with mineral precipitation on specific non-living organic cell surfaces. Recognition of these products is a direct marker of biological activity in time and space and is a key element in the study of the biological evolution and of its interactions with the geological processes. In this paper, primary carbonate cements from the Anisian microbial build-up of the ‘Monte Facito’ Formation (Basilicata region, Southern Italy) have been studied from a geobiological point of view. Optical microscopy, UV-epifluorescence and micro-Raman spectroscopy have been applied to investigate the organic mediation on their precipitation. The cements formed in microcavities or on grain substrates, and often show a microstromatolite-like pattern of growth. They are composed of alternations of cloudy organic and whitish inorganic bands that point to a double phase of mineralization. In the first phase, a biologically induced/influenced biomineralization is confirmed by the presence of organic matter strictly connected with the cloudy bands. This phase is followed by a pure abiotic mineralization that leads to the formation of whitish bands. This process repeated cyclically, ending at the complete filling of the microcavities or because of changes in the chemical conditions of the microsystem, for example, due to burial processes. This model of mineralization is similar to that proposed for primary cements forming in recent beach rocks. The Monte Facito Formation cements could be considered as the product of unconventional biomineralization, and the understanding of their growth process could provide an innovative tool in the research of biological signatures in the fossil record. The term unconventional is here utilized to discriminate this type of biomineralizations from those related to well-known biotic mineralization processes, like those involved in skeletons and microbialites growth, which can be considered as conventional biomineralizations.

Spent Labisia pumilia as a bulking agent for palm oil mill sludge composting

This paper aims to explore the potential use of herbal residue, spent Labisia pumilia (SLP) (also known as Kacip Fatimah) as a bulking agent for palm oil mill effluent sludge (POMES) composting to obtain biofertilizer. Natural aerobic decomposition through the passive aeration approach was implemented by using the bin-composting technique. POMES and SLP mixture were placed in three compost bins with a different weight ratio of 1:3, 1:1 and 3:1. Throughout the experimental period, samples were regularly taken out for physical analysis i.e. pH, temperature and moisture content. On day 90, samples were analyzed for nutrients analysis. The result indicated that ratios 1:1 and 1:3 illustrated typical pH and temperature profiles; meanwhile, ratio 3:1 vice versa for pH profiles. An in-depth analysis of the nutrients composition summarized that the C/N ratio for all mixture samples is within the standard limit for mature compost, and nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg) and calcium (Ca) are sufficient to utilize as a biofertilizer. In conclusion, it is feasible to utilize SLP as a bulking agent to improve palm oil mill sludge composting and eventually produce biofertilizer. Thus, it offers an alternative in handling solid waste from palm oil mills.

Forest litter constraints on the pathways controlling soil organic matter formation

The connection between litter chemistry and the pathways controlling soil organic matter (SOM) formation and decay in forest ecosystems remains poorly understood, particularly in tropical soils. We addressed this question by incubating samples of a Ferralsol for 200 days with typical forest litter (leaves, twigs, bark, and roots) obtained from 13C-enriched Eucalyptus seedlings. Throughout the incubation, we monitored 13C/12C–CO2 evolved from the soil to quantify the microbial respiration of the 13C-labeled fresh plant litter and of the native SOM. Afterwards, we used density fractionation to obtain particulate organic matter (POM) with density <1.8 g cm−3, and the soil material remaining was wet-sieved to obtain SOM with particle-size >53 μm and mineral-associated SOM (MAOM, with particle-size <53 μm). We used solid-state 13C-CPMAS-NMR spectroscopy to assess the molecular composition of plant material and SOM fractions and quantified microbial amino sugars in bulk soil using gas chromatography. Our 13C/12C–CO2 results indicate that leaves, twigs, and bark (aboveground litter) were respired at higher rates but led to lower degradation of native SOM as compared to root tissues. On average, aboveground litter promoted net C gains in both POM and MAOM, whereas root litter only led to net C gains in POM. Overall, SOM formation via microbial incorporation of aboveground litter through in vivo pathways appears to be more efficient and causes less degradation of native MAOM than roots. Moreover, a reduction in microbial amino sugars in bulk soils suggests that in vivo pathways also favored the formation of POM, which had more microbial-derived protein than forest litter. Therefore, the connection between litter chemistry and the pathways controlling SOM formation in tropical forest ecosystems must be included in a framework that also considers the mineralization of native SOM and the vertical separation of aboveground and belowground C inputs to soils.

Distribution and Sources of Carbon in Serpentinized Mantle Peridotites at the Atlantis Massif (IODP Expedition 357)

AbstractThe carbon geochemistry of serpentinized peridotites and gabbroic rocks recovered during IODP Expedition 357 on the Atlantis Massif (AM) was examined to characterize carbon sources and the fate of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in seawater during long‐lived hydrothermal circulation and serpentinization. Carbon isotopes reveal three stages of carbonate formation, starting at least 38,000 yr ago: (a) Early dispersed carbonate precipitation, with low water/rock ratios and high temperatures (50°C–190°C); (b) carbonate vein formation related to high and focused fluid fluxes still at high temperatures (30°C–200°C); and (c) seawater circulation leading to cold carbonate precipitation controlled by late, brittle fractures during uplift, and unroofing of the oceanic core complex. Our study reveals three main DIC sources in the system: (a) DIC from abiotic hydrothermal degradation of dissolved organic matter (OM); (b) DIC from seawater; and (c) DIC from mantle‐derived volatiles. Basement rocks containing dispersed carbonates are characterized by high concentrations (∼800 ppm) of total non‐carbonate carbon (NCC) and 13C‐depleted carbonates. We propose that high seawater fluxes in the southern part of the AM likely favor the transport and incorporation of marine DOC in serpentinites and that carbonates record isotopic signals of OM decay. Our study indicates that organic carbon accounts for a significant proportion of the total carbon stored in the AM and suggests that serpentinites may be an important sink of DOC from seawater.

Small World

Small World Michelle K. Angwenyi (bio) I was ten years old, beneath the waters of the Kilifi creek, when my father died. At the time, it was like a game; get in the water, don't be scared, my father was saying, you know how to swim, don't you? One foot fell into the cold water—a shiver passing through me, ignored—then the next. I held onto the side of the boat, my palms twisted backwards, chest curved outwards, before I held my breath, and, lit from within with the boyish amber of fearlessness, let go, into the water. It washed over me, blue and breathless, steady waves gently tossing me as I rose to the surface. See! I said to my father, I'm in! Giggling, I wiped my face with my palm, then I flopped onto my back, floating in the sunset as it sparkled over the water all around me. It was like a dream—the solid light, being carried flat by the ocean, bee-eaters chirping soft and round notes as they sped above me in somber murmurations, and then, dream of all dreams, my father was suddenly standing on the boat's edge, hands spread wide as if tacked to a cross. He hovered above me, a silhouette so sharp and strong against the sky, clouding the scene with a sudden shadow. The dream turned dark as I turned my face into the water to see where my father had fallen to, unable to open my eyes against the sting of salt water. You know how to swim, I asked myself from the inside, asking my father, don't you?! Today, all I saw was Seyed's back: curved, fragile, small. He didn't look as if he had any hands. He fell into the water like a heavy sack, unceremonious and full, folded, hefted. Moments before, we'd sailed out into the creek, a hot early September day that cooled into an evening tight with death. Moments before, he'd said, hey, here. Stop the boat here and, without asking, I did. Moments before, he'd looked at me, one last nod, mouthed a thank you, thank you so much, before he sat on the boat's edge, and quicker than any thought of intervention [End Page 116] would allow for, slid into the water with a silence so large, and yet so small, it hadn't been seen for years; a silence lodged into the spaces in his chest, a silence now expanding out into the breaking air. The smell of rotting flesh fills the air; an unjust trick of memory that refuses to let me grow up. I am again in a dream, the dream, floating on the ocean, looking up at my father who has turned into stone, and like a statue toppled from its dignified heights, falls into the water, feet up. When he finds me in the water, he isn't dead yet, and there is a pillow around my face, which he holds as he tries to suffocate me. We are both thrashing around in the water as I try to push the pillow away from my face—we both cannot breathe, not until one of us dies. They found me the day after my father died, shivering on the boat, wrapped in the coat he'd taken off just before he dove into the water. From his arms spread like wings, swift, almost imperceptibly, the coat came off, and he stretched his hands once more. And then his hands fell together again, only this time they came together in what looked like prayer; one last time before he leapt, long, into the water. A coat he loved so much, it seemed incomplete that he would die without it, my mother said to everyone after his death; said it again at the funeral. Nobody knows why he chose to leave that way, she said. ________ Seyed had come into my life, a bubble of contradictions, years and years ago. We were young then, racing through our twenties, even if in opposite directions. I was in Malindi, a waiter at an Italian restaurant, one of many that...

Dynamics of organic matter molecular composition under aerobic decomposition and their response to the nitrogen addition in grassland soils

Grassland soils store a substantial proportion of the global soil carbon (C) stock. The transformation of C in grassland soils with respect to chemical composition and persistence strongly regulate the predicted terrestrial-atmosphere C flux in global C biogeochemical cycling models. In addition, increasing atmospheric nitrogen (N) deposition alters C chemistry in grassland soils. However, there remains controversy about the importance of mineralogical versus biochemical preservation of soil C, as well as uncertainty regarding how grassland soil C chemistry responds to elevated N. This study used grassland soils with diverse soil organic matter (SOM) chemistries in an 8-month aerobic incubation experiment to evaluate whether the chemical composition of SOM converged across sites over time, and how SOM persistence responded to the N addition. This study demonstrates that over the course of incubation, the richness of labile compounds decreased in soils with less ferrihydrite content, whereas labile compounds were more persistent in ferrihydrite rich soils. In contrast, we found that the richness of more complex compounds increased over the incubation in most sites, independent of soil mineralogy. Moreover, we demonstrate the extent to which the diverse chemical composition of SOM converged among sites in response to microbial decomposition. N fertilization decreased soil respiration and inhibited the convergence of molecular composition across ecosystems by altering N demand for microbial metabolism and chemical interactions between minerals and organic molecules. This study provides original evidence that the decomposition and metabolism of labile organic molecules were largely regulated by soil mineralogy (physicochemical preservation), while the metabolism of more complex organic molecules was controlled by substrate complexity (biochemical preservation) independent to mineral-organic interactions. This study advanced our understanding of the dynamic biogeochemical cycling of C by unveiling that N addition dampened C respiration and diminished the convergence of SOM chemistry across diverse grassland ecosystems.

Variations in bacterial decay between cell types and between cell wall regions in waterlogged archaeological wood excavated in the intertidal zone

Abstract The bacterial decay of waterlogged archeological wood (WAW, hard pine spp.) taken from Daebudo shipwreck No. 2, which was buried in the intertidal zone in the mid-west coast (Yellow sea) of South Korea approximately 800 years ago, was investigated. The maximum moisture content of the outer parts (approx. 3 cm of depth) of WAW was approximately 4.2 times higher than that of undegraded reference pine wood. ATR-FTIR and solid-state 13C-NMR analysis indicated a relative increase of the lignin concentration in WAW caused by the degradation of cellulose and hemicelluloses across the board studied (31-cm-wide and 14.5-cm-thick board). Micromorphological studies also revealed that bacterial degradation was progressed to a depth of 15 cm (vertically 7.3 cm) from the surface, which is the innermost part of the board. Erosion bacteria (EB) were identified as the main degraders of WAW. Degradation by tunneling bacteria (TB) was occasionally detected. Decay resistance to bacterial attacks in WAW varied between cell types and between cell wall regions. Axial tracheids showed less resistance than ray tracheids, ray parenchyma cells, and axial intercellular canal cells, including strand tracheids, subsidiary parenchyma cells, and epithelial cells. Decay resistance was higher in ray tracheids and strand tracheids than in ray parenchyma cells and subsidiary parenchyma-/epithelial cells, respectively. Bordered- and cross-field pit membranes and the initial pit borders showed higher decay resistance than the tracheid cell walls. Overall, the S2 layer of the axial tracheids showed the weakest resistance to bacterial attacks.

Mycorrhizal effects on decomposition and soil CO2 flux depend on changes in nitrogen availability during forest succession

Abstract Mycorrhizal fungi play a central role in plant nutrition and nutrient cycling, yet our understanding on their effects on free‐living microbes, soil carbon (C) decomposition and soil CO2 fluxes remains limited. Here we used trenches lined with mesh screens of varying sizes to isolate mycorrhizal hyphal effects on soil C dynamics in subtropical successional forests. We found that the presence of mycorrhizal hyphae suppressed soil CO2 fluxes by 17% in early‐successional forests, but enhanced CO2 losses by 20% and 32% in mid‐ and late‐successional forests respectively. The inhibitory effects of mycorrhizal fungi on soil CO2 fluxes in the young stands were associated with changes in soil nitrogen (N) mineralization and microbial activities, suggesting that competition between mycorrhizae and saprotrophs for N likely suppressed soil C decomposition. In the mid‐ and late‐successional stands, mycorrhizal enhancement of CO2 release from soil likely resulted from both hyphal respiration and mycorrhizal‐induced acceleration of organic matter decay. Synthesis. Our results highlight the sensitivity of mycorrhizal fungi‐saprotroph interactions to shifts in nutrient availability and demand, with important consequences for soil carbon dynamics particularly in ecosystems with low nutrient conditions. Incorporating such interactions into models should improve the simulations of forest biogeochemical cycles under global change.

Metal Binding and Sources of Humic Substances in Recent Sediments from the Cananéia-Iguape Estuarine-Lagoon Complex (South-Eastern Brazil)

The Cananéia-Iguape estuarine–lagoon complex (São Paulo state, Brazil) is a natural laboratory to study metal binding by humic substances (HS) in subtropical settings. This transitional environment is evolving into a freshwater environment due to water input from the Ribeira River, funneled through the Valo Grande Canal (Iguape). Past mining activities in the Ribeira River basin and maritime traffic are suspected to be potential sources of trace metals in the system. In this study, the trace metal contents of Free Humic Acids (FHA), Bound Humic Acids (BHA), and Fulvic Acids (FA) extracted from sedimentary organic matter were investigated. Moreover, the sources of HS were traced using their stable carbon isotope compositions and C/N ratios. The results suggested a mixed marine–terrestrial source of FHA, BHA, and FA. Copper and Cr were the most abundant trace metals bound to HS. On average, Cu showed concentrations of 176, 115, and 37.9 μg g−1 in FHA, BHA, and FA, respectively, whereas Cr showed average concentrations of 47.4, 86.3, and 43.9 μg g−1 in FHA, BHA, and FA, respectively. Marine FHA showed the highest binding capacity for trace metals, whereas terrestrial FA derived from the decay of mangrove organic matter showed the lowest binding capacity.

Simultaneous biodegradation of harmful Cylindrospermopsis raciborskii and cylindrospermopsin toxin in batch culture by single Bacillus strain.

This study investigates the capability of a Bacillus flexus strain isolated from decayed cyanobacterial blooms for the bioremediation of Cylindrospermopsis raciborskii and cylindrospermopsin (CYN) toxin. The algicidal activity of this strain was tested by co-cultivation with C. raciborskii cultures. CYN biodegradation was investigated in the presence of living and heat-inactivated bacterial cells or bacterial filtrate. Living bacterial cells inhibited C. raciborskii growth after 2 days of incubation with complete cell death at day 5. Bacterial filtrate caused a rapid reduction in C. raciborskii growth at the first day, with complete cell lysis at day 3. Only living cells of SSZ01 caused reduction in CYN released into the medium during the bacterial decay of C. raciborskii cells. The biodegradation rate of CYN by SSZ01 relied on initial toxin concentrations. The highest rate (42 μg CYN L-1 day-1) was obtained at the higher initial concentration (300 μg L-1), and the lowest (4μg CYN L-1 day-1) was at lower concentration (50 μg L-1). These results suggest that this bacterial strain could be employed to bioremediate cyanobacterial blooms in freshwaters. Also, the application of this bacterium in slow sand filters would give possibilities for degradation and bioremediation of cyanotoxins in drinking water treatment plants.

The Canadian Federation of Earth Sciences Scientific Statement on Climate Change – Its Impacts in Canada, and the Critical Role of Earth Scientists in Mitigation and Adaptation

The Canadian Federation of Earth Sciences (CFES) has issued this statement to summarize the science, effects, and implications of climate change. We highlight the role of Earth scientists in documenting and mitigating climate change, and in managing and adapting to its consequences in Canada. CFES is the coordinated voice of Canada’s Earth Sciences community with 14 member organizations representing some 15,000 geoscientists. Our members are drawn from academia, industry, education, and government. The mission of CFES is to ensure decision makers and the public understand the contributions of Earth Science to Canadian society and the economy. Climate change has become a national and global priority for all levels of government. The geological record shows us that the global climate has changed throughout Earth’s history, but the current rates of change are almost unprecedented. Over the last 70 years, levels of common greenhouse gases (GHGs) in the atmosphere have steadily increased. Carbon dioxide (CO2) concentration is now 418 parts per million — its highest of the last three million years. The chemical (isotopic) composition of carbon in the atmosphere indicates the increase in GHGs is due to burning fossil fuels. GHGs absorb energy emitted from Earth’s surface and re-radiate it back, warming the lower levels of the atmosphere. Climatic adjustments that have recently occurred are, in practical terms, irreversible, but further change can be mitigated by lowering emissions of GHGs. Climate change is amplified by three important Earth system processes and effects. First, as the climate warms evaporation increases, raising atmospheric concentrations of water vapour, itself a GHG — and adding to warming. Second, loss of ice cover from the polar ice sheets and glaciers exposes larger areas of land and open water — leading to greater absorption of heat from the sun. Third, thawing of near-surface permafrost releases additional GHGs (primarily CO2 and methane) during decay of organic matter previously preserved frozen in the ground. Some impacts of climate change are incremental and steadily occurring, such as melting of glaciers and ice sheets, with consequent sea level rise. Others are intermittent, such as extreme weather events, like hurricanes — but are becoming more frequent. Summer water shortages are increasingly common in western Canada as mountain snowpacks melt earlier and summer river flows decline. In northern Canada, warming and thawing of near-surface permafrost has led to deterioration of infrastructure and increased costs for buildings that now require chilled foundations. Other consequences of unchecked climate change include increased coastal erosion, increases in the number and size of wildfires, and reduction in winter road access to isolated northern communities. Reductions in net GHG emissions are urgently required to mitigate the many effects of further climate change. Industrial and public works development projects must now assess the effects of climate change in their planning, design, and management. Cities, municipalities, and rural communities need to plan new residential development carefully to avoid enhanced risk of flooding, coastal erosion, or wildfire. Earth Science knowledge and expertise is integral to exploration and development of new metals and Earth materials required for a carbon-neutral future, and in the capture and storage of CO2 within the Earth. Earth Science is also central to society’s adaptation to new climatic regimes and reduction of risks. This includes anticipation, assessment, and management of extreme events, development of new standards and guidelines for geotechnical and engineering practice, and revision to regulations that consider climate change. Geoscientists also have an important role in the education of students and the public on the reasons for necessary action. Canada is uniquely positioned with its strong global geoscientific leadership, its vast landmass, and its northern terrain to effectively leverage research activities around climate change. Geoscience tools and geoscientists’ skills will be integral to Canada’s preparation for climate change.