Months Of Incubation Research Articles

Influence of compost maturation time on Cu and Zn mobility (M F) and redistribution (I R) in highly contaminated soil

This study examined how maturation time (3, 6 and 12 months) of sewage sludge compost added to soil contaminated with heavy metals (HMs), i.e., Cu and Zn affects: (1) the redistribution pattern of HMs; (2) metal mobility (as mobility factor, M F) and metal stability (as reduced partition index, I R); (3) rate constants of metal transformations in exchangeable and acid-soluble (F1) fraction and rate constants of metal redistribution in all fractions (F1–F4). Soil without amendments was used as a control. It was shown that compost maturation time did not affect metal redistribution. After 12 months of incubation in non-amended soil, Cu still showed medium mobility (M F = 16.5 %), while in amended soil it had low environmental risk (M F = 6.2 %). In contrast, Zn was highly mobile (M F = 43.4 %) in all treatments. Compost addition favored only Cu redistribution into more stable fractions. For both metals, the rate constants of redistribution were an order of magnitude lower than rate constants of metal transformations in the F1 fraction.

Uncultured Desulfobacteraceae and Crenarchaeotal group C3 incorporate 13C-acetate in coastal marine sediment.

Stable isotope probing (SIP) of deoxyribonucleic acid (DNA) was used to identify microbes incorporating (13) C-labeled acetate in sulfate-reducing sediment from Aarhus Bay, Denmark. Sediment was incubated in medium containing 10 mM sulfate and different (13) C-acetate (10, 1, 0.1 mM) concentrations. The resultant changes in microbial community composition were monitored in total and SIP-fractionated DNA during long-term incubations. Chemical analyses demonstrated metabolic activity in all sediment slurries, with sulfate-reducing activity largely determined by initial acetate concentrations. Sequencing of 16S rRNA gene PCR amplicons showed that the incubations shifted the bacterial but not the archaeal community composition. After 3 months of incubation, only sediment slurries incubated with 10 mM (13) C-acetate showed detectable (13) C-DNA labeling. Based on 16S rRNA and dsrB gene PCR amplicon sequencing, the (13) C-labeled DNA pool was dominated by a single type of sulfate reducer representing a novel genus in the family Desulfobacteraceae. In addition, members of the uncultivated Crenarchaeotal group C3 were enriched in the (13) C-labeled DNA. Our results were reproducible across biological replicate experiments and provide new information about the identities of uncultured acetate-consuming bacteria and archaea in marine sediments.

Biodegradation of HDPE by Aspergillus spp. from marine ecosystem of Gulf of Mannar, India

High density polyethylene (HDPE) is the most commonly found non-degradable solid waste among the polyethylene. In this present study, HDPE degrading various fungal strains were isolated from the polyethylene waste dumped marine coastal area and screened under in vitro condition. Based on weight loss and FT-IR Spectrophotometric analysis, two fungal strains designated as VRKPT1 and VRKPT2 were found to be efficient in HDPE degradation. Through the sequence analysis of ITS region homology, the isolated fungi were identified as Aspergillus tubingensis VRKPT1 and Aspergillus flavus VRKPT2. The biofilm formation observed under epifluorescent microscope had shown the viability of fungal strains even after one month of incubation. The biodegradation of HDPE film nature was further investigated through SEM analysis. HDPE poses severe environmental threats and hence the ability of fungal isolates was proved to utilize virgin polyethylene as the carbon source without any pre-treatment and pro-oxidant additives.

Effect of biochar, lime, and compost application on phosphorus adsorption in a Ferralsol

AbstractUse of biochar has multiple benefits like C, soil organic matter stabilization, and agricultural productivity. However, there is limited information about the effect of biochar on P dynamics in acidic soils. Hence, we investigated the effects of fresh and aged hydrothermal coal produced from bark (HTC) and low temperature coal synthesized from sewage sludge (LTC) on the kinetics of P adsorption in a Ferralsol. The treatments comprised of a control, compost [7.7 g (kg soil)−1], hydrothermal carbonization coal [HTC, 2 g (kg soil)−1], low temperature conversion coal [LTC, 3.8 g (kg soil)−1], lime [0.3 g CaO (kg soil)−1], compost + HTC [3.8 + 1.0 g (kg soil)−1], compost + LTC [3.8 + 1.9 g (kg soil)−1, respectively], compost + lime [7.6 and 0.4 g (kg soil)−1, respectively]. The soil samples were incubated for a period of 3 months at 60% of the maximum water holding capacity. After 5 d and 3 months of the incubation period soil pH, Ca‐acetate lactate (CAL) extractable soil‐P, and P‐adsorption isotherms were determined. The results show a significant effect of treatments on soil pH just after 5 d, which remained consistent after three months of incubation. All treatments, except HTC increased the soil pH compared with the control treatment. The maximum increase in soil pH was observed with compost + lime (from 4.5 to 6.1). The CAL‐extractable P was significantly increased with application of LTC, compost + LTC, and compost + lime. The sorption parameters were not affected after 5 d of incubation. Due to residence effects, the P sorption capacity (Sm) was significantly reduced in the LTC treatment [from 1182 to 1099 mg (kg soil)−1], and in the combination treatments compost + HTC [from 1182 to1078 mg (kg soil)−1], and compost + LTC [from 1182 to 1099 mg (kg soil)−1] treatments. The P binding energy (K) was significantly increased by the addition of LTC (from 2.18 to 4.26 mg L−1), lime (from 2.18 to 4.53 mg L−1), compost + HTC (from 2.18 to 7.03 mg L−1) and compost + LTC (from 2.18 to 4.68 mg L−1). Based on the results of the present study it is concluded that alone application of biochars do not alter the P bioavailability and sorption in a Ferralsol. However, combined application of biochars along with compost significantly decreases P sorption and increases bioavailability.

Accumulation and oxidation of elemental mercury in tropical soils

The role of chemical and mineralogical soil properties in the retention and oxidation of atmospheric mercury in tropical soils is discussed based on thermal desorption analysis. The retention of gaseous mercury by tropical soils varied greatly both quantitatively and qualitatively with soil type. The average natural mercury content of soils was 0.08±0.06μgg−1 with a maximum of 0.215±0.009μgg−1. After gaseous Hg0 incubation experiments, mercury content of investigated soils ranged from 0.6±0.2 to 735±23μgg−1, with a mean value of 44±146μgg−1. Comparatively, A horizon of almost all soil types adsorbed more mercury than B horizon from the same soil, which demonstrates the key role of organic matter in mercury adsorption. In addition to organic matter, pH and CEC also appear to be important soil characteristics for the adsorption of mercury. All thermograms showed Hg2+ peaks, which were predominant in most of them, indicating that elemental mercury oxidized in tropical soils. After four months of incubation, the thermograms showed oxidation levels from 70% to 100%. As none of the samples presented only the Hg0 peak, and the soils retained varying amounts of mercury despite exposure under the same incubation conditions, it became clear that oxidation occurred on soil surface. Organic matter seemed to play a key role in mercury oxidation through complexation/stabilization of the oxidized forms. The lower percentages of available mercury (extracted with KNO3) in A horizons when compared to B horizons support this idea.

Changes in the dissolved organic matter leaching from soil under severe temperature and N-deposition.

In this study, we conducted growth chamber experiments using three types of soil (wetland, rice paddy, and forest) under the conditions of a severe increase in the temperature and N-deposition in order to investigate how extreme weather influences the characteristics of the dissolved organic matter (DOM) leaching from different soil types. This leachate controls the quantity and quality of DOM in surface water systems. After 5 months of incubation, the dissolved organic carbon (DOC) concentrations decreased in the range of 21.1 to 88.9 %, while the specific UV absorption (SUVA) values increased substantially in the range of 19.9 to 319.9 % for all of the samples. Higher increases in the SUVA values were observed at higher temperatures, whereas the opposite trend was observed for samples with N-addition. The parallel factor analysis (PARAFAC) results showed that four fluorescence components: terrestrial humic-like (component 1 (C1)), microbial humic-like (component 2 (C2)), protein-like (component 3 (C3)), and anthropogenic humic-like (component 4 (C4)) constituted the fluorescence matrices of soil samples. During the experiment, labile DOM from the soils was consumed and transformed into resistant aromatic carbon structures and less biodegradable components via microbial processes. The principle component analysis (PCA) results indicated that severe temperatures and N-deposition could enhance the contribution of the aromatic carbon compounds and humic-like components in the soil samples.

Changes in Chemistry of Rice Husk Compost and Its Effect on Negative Charge and Nutrient Content of a Chemically Degraded Oxisol

Rice husk application and its long-term effects on charge characteristics and elemental composition of a chemically degraded Oxisol have not been rigorously studied. The objective of the study was to determine the ability of composted rice husk (CRH) to preserve organic carbon (C), generate negative charge, and release various ions in heavy clay Oxisol. The topsoil and subsoil, representing natural and erosion conditions, respectively, were incubated with CRH for 24 months. Results showed carbon types of CRH, as revealed by solid-state cross-polarization magic angle spinning 13C nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy, were relatively unchanged from months 5 to 12 after incubation, indicating limited decomposition. Carbon types were dominated by O-alkyl and di-O-alkyl C with small proportions of alkyl, methoxyl, aromatic, phenolic, and carboxyl C. After 24 months of incubation, O-alkyl and di-O-alkyl C decreased, indicating susceptibility, whereas alkyl, methoxyl, aromatic, and phenolic C increased, indicating resistance to decomposition. Values of pH0 and point zero net charge (PZNC) were measured using potentiometric titration and ion adsorption indices, respectively. Values of pH0 and PZNC decreased during CRH incubation for both topsoil and subsoil, suggesting the increase of soil negative charge. Total negative charge for topsoil and subsoil increased from 2.7 to 3.5 cmolc/kg and 2.5 to 3.2 cmolc/kg, respectively. This reflects that CRH was able to mask soil positive charge to increase negative charge. In situ soil solution study indicated CRH could release various elements in the order of potassium (K) > sulfur (S) > natrium (Na) > silicon (Si) > magnesium (Mg) > calcium (Ca). In addition, toxic elements, aluminum (Al) and manganese (Mn), were significantly suppressed. The implication of the study is that CRH offers a means to increase cation exchange capacity and nutrient content of highly weathered soils while preserving organic C, thereby reducing CO2 emission from agriculture.

The role of organic matter in ameliorating acid sulfate soils with sulfuric horizons

Acid sulfate soils with sulfuric horizons (pH<4) can exert a range of negative impacts on the ecology and productivity of soils. The primary treatment for these soils is to raise the pH of the sulfuric horizons using lime. Although often effective, this treatment can be expensive and not well suited to large areas. In this laboratory study, we have investigated the possible use of plant organic matter (OM) to ameliorate: (i) “sulfuric soils” [produced by the oxidization of clayey sulfidic material (pH>4) samples to form “sulfuric horizon material” (pH<4)] and (ii) “neutralized sulfuric soils” [produced by the neutralization of peaty sulfuric horizon material (pH<4) with alkaline sandy loam]. The advantage of this approach is that organic matter is readily available and inexpensive. The experimental treatments used leaf material from Phragmites australis as the source of organic matter, which was either incorporated into the two manufactured soils or applied to the surface. After 6months of incubation under either aerobic or anaerobic soil conditions, pH, Eh and sulfate content were measured. The results showed that incorporation of OM into the sulfuric soil significantly increased soil pH, the extent depending on the moisture level. Changes in pH and sulfate content were correlated with Eh. Application of OM to the “neutralized sulfuric soil” was only partially effective in preventing acidification. It was concluded that the decomposition of OM by aerobic bacteria results in oxygen depletion, which then favors metabolic conversion of sulfates to sulfides by anaerobic bacteria. The results of this study have important implications for the broad scale management of acid sulfate soils.

Olive-pomace harbors bacteria with the potential for hydrocarbon-biodegradation, nitrogen-fixation and mercury-resistance: Promising material for waste-oil-bioremediation

Olive-pomace, a waste by-product of olive oil industry, took up >40% of its weight crude oil. Meanwhile, this material harbored a rich and diverse hydrocarbonoclastic bacterial population in the magnitude of 106 to 107 cells g−1. Using this material for bioaugmentation of batch cultures in crude oil-containing mineral medium, resulted in the consumption of 12.9, 21.5, 28.3, and 43% oil after 2, 4, 6 and 8 months, respectively. Similar oil-consumption values, namely 11.0, 29.3, 34.7 and 43.9%, respectively, were recorded when a NaNO3-free medium was used instead of the complete medium. Hydrocarbonoclastic bacteria involved in those bioremediation processes, as characterized by their 16S rRNA-gene sequences, belonged to the genera Agrococcus, Pseudomonas, Cellulosimicrobium, Streptococcus, Sinorhizobium, Olivibacter, Ochrobactrum, Rhizobium, Pleomorphomonas, Azoarcus, Starkeya and others. Many of the bacterial species belonging to those genera were diazotrophic; they proved to contain the nifH-genes in their genomes. Still other bacterial species could tolerate the heavy metal mercury. The dynamic changes of the proportions of various species during 8 months of incubation were recorded. The culture-independent, phylogenetic analysis of the bacterioflora gave lists different from those recorded by the culture-dependent method. Nevertheless, those lists comprised among others, several genera known for their hydrocarbonoclastic potential, e.g. Pseudomonas, Mycobacterium, Sphingobium, and Citrobacter. It was concluded that olive-pomace could be applied in oil-remediation, not only as a physical sorbent, but also for bioaugmentation purposes as a biological source of hydrocarbonoclastic bacteria.

Phase behavior of binary mixture systems of saturated-unsaturated mixed-acid triacylglycerols: effects of glycerol structures and chain-chain interactions.

We systematically examined the phase behavior of binary mixtures of mixed-acid triacylglycerols (TAGs) containing palmitic and oleic acid moieties 1,3-dioleoyl-2-palmitoyl-glycerol (OPO), 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO), and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP), which are widely present in natural fats and are employed in the food, pharmaceutical, and cosmetic industries. Differential scanning calorimetry and X-ray diffraction methods were applied to observe the mixing behavior of PPO/OPO, OOP/OPO, and PPO/OOP under metastable and stable conditions. The results led to three conclusions: (1) Eutectic behavior was observed in PPO/OPO. (2) Molecular compound (MC) crystals were formed in the mixtures of OOP/OPO and PPO/OOP. (3) However, the MC crystals occurred only under metastable conditions and tended to separate into component TAGs to form eutectic mixture systems after 17 months of incubation. These results were contrary to those of previous studies on 1,3-dipalmitoyl-2-oleoyl glycerol (POP)/OPO and POP/PPO in which the MC crystals were thermodynamically stable. We determined that specific molecular interactions may cause this different phase behavior (stability of POP/OPO and POP/PPO MC crystals and metastability of OOP/OPO and PPO/OOP MC crystals). All results confirm the significant effects of molecular structures of glycerol groups, interactions of fatty acid chains, and polymorphism of the component TAGs on the mixing behavior of mixed-acid TAGs.

English

The potential of Pleurotus pulmonarius and Pleurotus ostreatus on the degradation of PAHs in spent and fresh cutting fluids (SCF and FCF) contaminated soils was investigated. Different weights of soil samples were contaminated with varying composition (10, 20 or 30%) of spent and fresh cutting fluids separately then inoculated each sample with P. pulmonarius and P. ostreatus separately and incubated at 28 &plusmn; 2&deg;C for two months. The samples were analyzed in triplicates for 16 priority polycyclic aromatic hydrocarbons (PAHs) by gas chromatography after extracting with hexane and dichloromethane (3:1). The initial PAHs in the cutting fluids were mainly composed of 2 to 6 fused benzene rings. Significant reductions in PAHs concentrations for SCF and FCF were observed after two months of incubation. The percentage total PAHs remaining in FCF soil ranged from 71.7 to 73.6% when inoculated with P. pulmonarius and 0.93 to 31.0% when inoculated with P. ostreatus. Similarly, the percentage total PAHs remaining in SCF soil ranged from 42.6 to 72.6% when inoculated with P. pulmonarius and 54.9 to 62.2% when inoculated with P. ostreatus. Overall range of PAHs degradation by P. pulmonarius inoculated on FCF contaminated soil was 17.3 to 27.3%, while for P. ostreatus inoculated soil was 69.0 to 99.07% at different contamination levels. In contrast, overall PAHs degradation for P. pulmonarius and P. ostreatus inoculated on SCF ranged from 27.4 to 57.4% and from 37.8 to 45.2%, respectively. Thus, P. ostreatus is found more effective as a biodegradation agent for PAHs in contaminated soils when compared with P. pulmonarius. &nbsp; Key words: Biodegradation, polycyclic aromatic hydrocarbons (PAHs), cutting fluids, Pleurotus ostreatus, Pleurotus pulmonarius.

Enzyme Dehydration Using Microglassification™ Preserves the Protein's Structure and Function

Controlled enzyme dehydration using a new processing technique of Microglassification™ has been investigated. Aqueous solution microdroplets of lysozyme, α-chymotrypsin, catalase, and horseradish peroxidase were dehydrated in n-pentanol, n-octanol, n-decanol, triacetin, or butyl lactate, and changes in their structure and function were analyzed upon rehydration. Water solubility and microdroplet dissolution rate in each solvent decreased in the order: butyl lactate > n-pentanol > triacetin > n-octanol > n-decanol. Enzymes Microglassified™ in n-pentanol retained higher activity (93%-98%) than n-octanol (78%-85%) or n-decanol (75%-89%), whereas those Microglassified™ in triacetin (36%-75%) and butyl lactate (48%-79%) retained markedly lower activity. FTIR spectroscopy analyses showed α-helix to β-sheet transformation for all enzymes upon Microglassification™, reflecting a loss of bound water in the dried state; however, the enzymes reverted to native-like conformation upon rehydration. Accelerated stressed-storage tests using Microglassified™ lysozyme showed a significant (p < 0.01) decrease in enzymatic activity from 46,560 ± 2736 to 31,060 ± 4327 units/mg after 3 months of incubation; however, it was comparable to the activity of the lyophilized formulation throughout the test period. These results establish Microglassification™ as a viable technique for enzyme preservation without affecting its structure or function.

The pH-dependent long-term stability of an amorphous manganese oxide in smelter-polluted soils: Implication for chemical stabilization of metals and metalloids

An amorphous manganese oxide (AMO) and a Pb smelter-polluted agricultural soil amended with the AMO and incubated for 2 and 6 months were subjected to a pH-static leaching procedure (pH 3–8) to verify the chemical stabilization effect on metals and metalloids. The AMO stability in pure water was pH-dependent with the highest Mn release at pH 3 (47% dissolved) and the lowest at pH 8 (0.14% dissolved). Secondary rhodochrosite (MnCO3) was formed at the AMO surfaces at pH>5. The AMO dissolved significantly less after 6 months of incubation. Sequential extraction analysis indicated that “labile” fraction of As, Pb and Sb in soil significantly decreased after AMO amendment. The pH-static experiments indicated that no effect on leaching was observed for Cd and Zn after AMO treatments, whereas the leaching of As, Cu, Pb and Sb decreased down to 20%, 35%, 7% and 11% of the control, respectively. The remediation efficiency was more pronounced under acidic conditions and the time of incubation generally led to increased retention of the targeted contaminants. The AMO was found to be a promising agent for the chemical stabilization of polluted soils.

On-farm solid state simultaneous saccharification and fermentation of whole crop forage rice in wrapped round bale for ethanol production.

BackgroundIn an attempt to reduce environmental loading during ethanol production from cellulosic plant biomass, we have previously proposed an on-site solid state fermentation (SSF) method for producing ethanol from whole crops, which at the same time provides cattle feed without producing wastes. During the ensiling of freshly harvested plant biomass with cellulase and glucoamylase, the added yeast and lactic acid bacteria induced simultaneous saccharification and production of ethanol and lactic acid in hermetically sealed containers on-farm. In a previous study, laboratory-scale SSF (using 250 g of fresh rice crop biomass) yielded 16.9 weight % ethanol in dry matter (DM) after 20 days of incubation. In this study, the fermentation volume was scaled up to a normal-sized round bale and the fermentation process (ethanol concentrations of the products) was monitored. The ethanol produced was recovered and the recovery efficiency was evaluated.ResultsSSF tests with forage rice round bales using polyethylene-wrapped whole plant materials (cultivar Leaf Star, average of 125.2 kg dry weight) were monitored in the field without temperature control. They yielded 14.0 weight % ethanol and 2.9 weight % lactic acid in DM after six months of incubation, and the ethanol ratio in the bale remained stable for 14 months after processing. SSF tests with three different rice cultivars were conducted for three years. Ethanol recovery from a fermented whole bale (244 kg fresh matter (FM) containing about 12.4 kg ethanol) by one-step distillation using vacuum distillation equipment yielded 86.3% ethanol collected from distilled solution (107 kg of 10.0 weight % ethanol). In addition, an average of 1.65 kg ethanol in 40.8 kg effluent per bale was recovered. Relative nitrogen content was higher in SSF products than in silage made from the same plant material, indicating that fermentation residue, whose quality is stabilized by the lactic acid produced, can be used as cattle feed.ConclusionsWe have successfully demonstrated an efficient on-site ethanol production system with non-sterilized whole rice crop round bale. However, issues concerning the establishment of the ethanol recovery procedure on-site and evaluation of the fermentation residue as cattle feed have to be addressed.

Atributos químicos da solução e do solo após aplicação de resíduo da extração de celulose

Este trabalho objetivou avaliar, em casa de vegetação e usando colunas de solo e ciclos de umedecimento, o efeito da aplicação de resíduos da extração de celulose sobre a composição química do solo e da solução extraída de dois Latossolos Vermelhos. O delineamento experimental utilizado foi inteiramente casualizado. Os tratamentos utilizados foram: T1 - Sem adição de calcário e resíduo (testemunha); T2 - 1,0 t ha-1 de calcário calcítico; T3 - 1,2 t ha-1 de dregs/grits; T4 - 0,8 t ha-1 de lama de cal; T5 - 2,4 t ha-1 de cinza; T6 - 1,8 t ha-1 de dregs/grits + lama de cal + cinza na proporção 1:3:6; T7 - 1,0 t ha-1 de dregs/grits + lama de cal na proporção 1:3. A avaliação da composição química da solução extraída de cada solo estudado, foi realizada durante quatro meses de incubação e análises químicas do solo, após este período. Os resultados foram analisados efetuando-se a análise de variância e o teste de Tukey para as comparações de média no nível de 0,05 de probabilidade. Dentre os tratamentos aplicados o 1,2 t ha-1 de dregs/grits pode não ser adequado para utilização no solo visto que transferiu maior concentração de Na+ para a solução do solo em relação ao recomendado pela literatura enquanto o tratamento 2,4 t ha-1 de cinza pode ser utilizado como fonte de K ao solo.

Speciation and lability of Ag-, AgCl-, and Ag2S-nanoparticles in soil determined by X-ray absorption spectroscopy and diffusive gradients in thin films.

Long-term speciation and lability of silver (Ag-), silver chloride (AgCl-), and silver sulfide nanoparticles (Ag2S-NPs) in soil were studied by X-ray absorption spectroscopy (XAS), and newly developed “nano” Diffusive Gradients in Thin Films (DGT) devices. These nano-DGT devices were designed specifically to avoid confounding effects when measuring element lability in the presence of nanoparticles. The aging profile and stabilities of the three nanoparticles and AgNO3 (ionic Ag) in soil were examined at three different soil pH values over a period of up to 7 months. Transformation of ionic Ag, Ag-NP and AgCl-NPs were dependent on pH. AgCl formation and persistence was observed under acidic conditions, whereas sulfur-bound forms of Ag dominated in neutral to alkaline soils. Ag2S-NPs were found to be very stable under all conditions tested and remained sulfur bound after 7 months of incubation. Ag lability was characteristically low in soils containing Ag2S-NPs. Other forms of Ag were linked to higher DGT-determined lability, and this varied as a function of aging and related speciation changes as determined by XAS. These results clearly indicate that Ag2S-NPs, which are the most environmentally relevant form of Ag that enter soils, are chemically stable and have profoundly low Ag lability over extended periods. This may minimize the long-term risks of Ag toxicity in the soil environment.

Effects of endogeic earthworms on the soil organic matter dynamics and the soil structure in urban and alluvial soil materials

Earthworms are considered as key actors of soil processes at different spatial and temporal scales and provide essential ecosystem services linked to climate regulation or primary production. However, little is known about their basic functional roles (e.g. organic matter decomposition, soil structuring processes) in perturbed systems such as urban or alluvial soils. Alluvial soils are characterized by regular physical perturbation through flooding and associated erosion/sedimentation processes which are rather similar to perturbations (e.g. temporal instability, spatial heterogeneity) affecting urban soils. Due to their close soil characteristics, we hypothesized that in both cases, soil functioning is similar with respect to soil fauna activity. Under controlled conditions, our objective was to investigate the effects of two endogeic earthworm species, Allolobophora chlorotica (pink morph) and Aporrectodea rosea (the two most abundant species found in the studied urban site), on soil organic matter (SOM) dynamics and soil structure (network of earthworm burrows) comparing an urban and an alluvial soil. We investigated the growth of individuals (weight gain and reproduction success) and assessed their effects on SOM decomposition (cumulative C–CO2 emission, nitrogen and phosphorus mineralization) and soil structure (macroporosity, total length and connectivity of segments) after one and three months of incubation. Our results showed higher growth of A. rosea in the alluvial soil compared to the urban soil. However, the total length of burrows, carbon and nitrogen mineralization were often higher in the urban soil especially when the two species were combined. This trend can be mainly explained by lower organic matter content found in the urban soil which may influence positively the burrowing activity and negatively the growth of earthworms. Endogeic earthworms appear a key feature of the soil functioning in the urban context through their roles on organic matter transformation, the formation and maintenance of the soil structure.

Bottom–up and top–down mechanisms indirectly mediate interactions between benthic biotic ecosystem components

The loss or decline in population size of key species can instigate a cascade of effects that have implications for interacting species, therewith impacting biodiversity and ecosystem functioning. We examined how top–down and bottom–up interactions may mediate knock-on effects of a coastal deposit-feeding clam, Macomona liliana (hereafter Macomona), on sandflat meiobenthos densities. Therefore we manipulated densities of Macomona in combination with predator exclusion and experimental shading that was expected to alter microphytobenthos biomass. We show that Macomona regulated densities of meiobenthic (38–500μm) nematodes, copepods, polychaetes, turbellarians, and ostracodes during the three months of incubation via indirect mechanisms. Predator pressure on Macomona by eagle rays (Myliobatis tenuicaudatus) was found to have a negative effect on densities of some meiobenthic taxa. Furthermore, experimental shading resulted in the loss of a positive relation between Macomona and microphytobenthos biomass, while concurrently increasing the density of some meiobenthic taxa. We suggest that this observation can be explained by the release from bioturbation interference effects of the cockle Austrovenus stutchburyi that was found to thrive in the presence of Macomona under non-shaded conditions. Our results highlight the importance of interactions between macrofaunal bioturbation, microphyte biomass, sediment stability, and predation pressure for the structuring of benthic communities. This experiment illustrates that manipulative field experiments may be particularly suitable to study such multiple indirect mechanisms that regulate ecosystem diversity and related functioning because such approaches may best capture the complex feedbacks and processes that determine ecosystem dynamics.

Intermediate complex morphophysiological dormancy in seeds of the cold desert sand dune geophyte Eremurus anisopterus (Xanthorrhoeaceae; Liliaceae s.l.).

Little is known about morphological (MD) or morphophysiological (MPD) dormancy in cold desert species and in particular those in Liliaceae sensu lato, an important floristic element in the cold deserts of Central Asia with underdeveloped embyos. The primary aim of this study was to determine if seeds of the cold desert liliaceous perennial ephemeral Eremurus anisopterus has MD or MPD, and, if it is MPD, then at what level. Embryo growth and germination was monitored in seeds subjected to natural and simulated natural temperature regimes and the effects of after-ripening and GA3 on dormancy break were tested. In addition, the temperature requirements for embryo growth and dormancy break were investigated. At the time of seed dispersal in summer, the embryo length:seed length (E:S) ratio was 0·73, but it increased to 0·87 before germination. Fresh seeds did not germinate during 1 month of incubation in either light or darkness over a range of temperatures. Thus, seeds have MPD, and, after >12 weeks incubation at 5/2 °C, both embryo growth and germination occurred, showing that they have a complex level of MPD. Since both after-ripening and GA3 increase the germination percentage, seeds have intermediate complex MPD. Embryos in after-ripened seeds of E. anisopterus can grow at low temperatures in late autumn, but if the soil is dry in autumn then growth is delayed until snowmelt wets the soil in early spring. The ecological advantage of embryo growth phenology is that seeds can germinate at a time (spring) when sand moisture conditions in the desert are suitable for seedling establishment.

Ocean acidification impacts mussel control on biomineralisation.

Ocean acidification is altering the oceanic carbonate saturation state and threatening the survival of marine calcifying organisms. Production of their calcium carbonate exoskeletons is dependent not only on the environmental seawater carbonate chemistry but also the ability to produce biominerals through proteins. We present shell growth and structural responses by the economically important marine calcifier Mytilus edulis to ocean acidification scenarios (380, 550, 750, 1000 µatm pCO2). After six months of incubation at 750 µatm pCO2, reduced carbonic anhydrase protein activity and shell growth occurs in M. edulis. Beyond that, at 1000 µatm pCO2, biomineralisation continued but with compensated metabolism of proteins and increased calcite growth. Mussel growth occurs at a cost to the structural integrity of the shell due to structural disorientation of calcite crystals. This loss of structural integrity could impact mussel shell strength and reduce protection from predators and changing environments.