Aerobic Microbial Degradation Research Articles

Soil geochemistry of hydrogen and other gases along the San Andreas fault

Natural hydrogen has generated great interest as a potential clean and renewable energy source. To understand the occurrence of natural hydrogen, 103 1-m deep soil gas samples were acquired near the San Andreas Fault at Jasper Ridge and Portola Valley, California, USA. The gas samples were analyzed for hydrogen, helium, carbon dioxide, light hydrocarbons, and fixed gas concentrations. Statistical data analysis was carried out to group samples, reveal their spatial distribution, and understand possible sources of the gases.High concentrations of hydrogen up to 20.3 ppmv and 17.3 ppmv occur in Jasper Ridge and Portola Valley, respectively, ∼30–35 times greater than the atmospheric concentration. Most samples with high hydrogen concentrations fall on or near faults, suggesting an origin by serpentinization or geomechanical activation of catalytic sites in minerals, although a deep-seated primordial origin cannot be excluded. Elevated concentrations of carbon dioxide resulted from aerobic microbial degradation of organic matter and elevated concentrations of light hydrocarbons likely resulted from thermal cracking of organic matter.

Anaerobic–anoxic–oxic biological treatment of high-strength, highly recalcitrant polyphenylene sulfide wastewater

This paper outlines an integrated anaerobic–anoxic–oxic (A2O) treatment scheme for high-strength, highly recalcitrant wastewater from the production of polyphenylene sulfide (PPS) resins and their composite chemicals. An integrated anaerobic granular sludge blanket (GSB) and anoxic–oxic (AO) reactor indicated that the A2O removed chemical oxygen demand (COD) of up to 7,043 mg/L with no adverse impact from high total dissolved solids (25,000 mg/L) on the GSB COD removal and effluent suspended solids. At a Total Kjeldahl Nitrogen (TKN) nitrification load of 0.11 g TKN/L.d and 400 mg NH3/L, almost 99 % of the NH3 was degraded with effluent NH3 < 5 mg/L, meeting the limit of 35 mg/L. High S2- levels of up to 1470 mg/L can be transformed through aerobic microbial degradation to meet a limit of 1.0 mg/L. With proper microbial acclimation and process designs, the integrated A2O scheme offers a resilient and robust treatment for high-strength recalcitrant PPS wastewater.

Tapping Carbon Sequestration Potential of Blooming Macroalgae to Mitigate Climate Change

Macroalgal mariculture is gaining global attention to achieve carbon neutrality due to its important contribution to ocean carbon sequestration. However, some wild macroalgal species (e.g., Sargassum and Ulva prolifera ) exhibit strong environmental adaptability and can cause large-scale, recurrent blooms in global oceans, fueled by rising atmospheric CO 2 levels and coastal eutrophication. Notably, massive Ulva prolifera green tides have occurred annually in the Yellow Sea for the past 17 consecutive years. At the late blooming stage, millions of tons of U. prolifera naturally sink to the shallow seafloor. The subsequent intense microbial aerobic degradation of sinking macroalgae results in coastal hypoxia and acidification, with most of the macroalgal carbon returning to the atmosphere. Preventing or reducing the intense degradation of massive sinking U. prolifera could enable more macroalgal carbon storage in the ocean in the long term and alleviate the harmful effects of green tide. Thus, ecological disasters from macroalgal blooms may be transformed into useful natural platforms to increase ocean carbon sequestration. We propose an integrated strategy using environmentally friendly minerals (e.g., montmorillonite and calcium carbonate) and coagulants (e.g., polyaluminum chloride), along with natural algicidal bacteria or substances, to induce rapid flocculation and sedimentation of blooming macroalgae, reduce the degradation of sinking macroalgae and its negative environmental impacts, and minimize the generation of macroalgal propagules or seeds and the potential risk for future green tide outbreaks. This integrated approach is potentially a promising approach to tap the carbon sequestration potential of macroalgal blooms to mitigate climate change.

NSO-bearing compounds in severely–extremely biodegraded crude oil revealed by ESI(-) FT-ICR MS

The heavy oil is essentially comprised of asphaltene and nitrogen, sulphur, and oxygen-bearing (NSO) compounds, which records the alteration processes of aerobic biodegradation. In this study, six biodegraded oils were geochemically examined using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in negative-ion electrospray ionization (ESI(-)) mode to decipher the NSO heteroatom compounds molecular compositions. The results reveal that the NSO compounds, especially those strongly resistant to biodegradation, i.e., alcohol/phenols, carboxylic acids with various alkyl substitution, naphthenic acids with 2 to 5 naphthenic/aromatic rings, nitrogen- and sulphur-bearing carboxylic acids, and hydroxy acids (O3) and dibasic acids (O4) are enriched in biodegraded oils. The O1, N1O1, and O1S1 classes appear in trace amounts in severely to extremely biodegraded oils (PM > 7) but are abundant in moderately biodegraded oils (PM < 7), implying the alcohol group generated by biodegradation are further oxidized to form a carboxylic acid with the progressively biodegraded process. Abnormal enrichment of O2 and O4 classes was trapped in the severely–extremely biodegraded oils, implying the generation of additional monobasic acid/dibasic acids during microbial aerobic degradation of crude oils. Besides, the relative content of monocyclic naphthenic acid (DBE = 2) gradually decreased with biodegradation level, while those of the bicyclic-, tricyclic-, and tetracyclic–naphthenic acid (DBE = 3-5) showed an increasing trend. The newly developed proxies of NSO compounds (i.e., the ratios of biodegradation products with different numbers of oxygen atoms of the specified compound, and the O2, O3, O4, and O5 classes with various DBE values and/or various carbon numbers) agreed well with the existing biodegradation indicators (i.e., C2925-NH/C30H, C2117-NT/C23TT, C27DS/C27RS, and C28TAS/C21TAS), confirming the availability of ESI(-) FT-ICR MS to distinguish the biodegraded oils with high resolution.

Bioponics as a Promising Approach to Sustainable Agriculture: A Review of the Main Methods for Producing Organic Nutrient Solution for Hydroponics

Hydroponics is a soilless cultivation technique in which plants are grown in a nutrient solution typically made from mineral fertilizers. This alternative to soil farming can be advantageous in terms of nutrient and water use efficiency, plant pest management, and space use. However, developing methods to produce nutrient solutions based on local organic materials is crucial to include hydroponics within a perspective of sustainability. They would also allow hydroponics to be developed in any context, even in remote areas or regions that do not have access to commercial fertilizers. This emerging organic form of hydroponics, which can be qualified as “bioponics”, typically recycles organic waste into a nutrient-rich solution that can be used for plant growth. Many methods have been developed and tested in the past three decades, leading to greatly heterogenous results in terms of plant yield and quality. This review describes the main organic materials used to produce nutrient solutions and characterizes and categorizes the different types of methods. Four main categories emerged: a “tea”-type method, an aerobic microbial degradation method, an anaerobic digestion method, and a combined anaerobic-aerobic degradation method. The advantages and drawbacks of each technique are discussed, as well as potential lines of improvement. This aims at better understanding the links between agronomic results and the main biochemical processes involved during the production, as well as discussing the most suitable method for certain plants and/or contexts.

Carbon and hydrogen stable isotope fractionation of sulfamethoxazole during anaerobic transformation catalyzed by Desulfovibrio vulgaris Hildenborough

The fate of antibiotics in aquatic environments is of high concern and approaches are needed to assess the transformation of antibiotics in wastewater treatment plants. Here we used the model organism Desulfovibrio vulgaris Hildenborough to analyze compound specific isotope fractionation associated with anaerobic transformation of the antibiotic sulfamethoxazole (SMX). The results show that the rearrangement of the isoxazole ring in SMX is leading to significant carbon and hydrogen isotopic fractionation (εC = −5.8 ± 0.7‰, εH = −34 ± 9‰) during anaerobic transformation. The observed carbon isotopic fractionation is significantly higher than the values reported for aerobic degradation (εC = −0.6 ± 0.1‰) or abiotic reactions (εC = −0.8 to −4.8‰ for photolysis, εC = −0.8 to −2.2‰ for advanced oxidation). This indicates that carbon isotope fractionation can be used as a parameter to differentiate reaction mechanisms of SMX transformation. The corresponding apparent kinetic isotope effect (AKIEC) for anaerobic transformation of SMX was 1.029 ± 0.003, suggesting that the mechanism for anaerobic transformation is distinct from the mechanism reported for microbial aerobic degradation (AKIEC = 1.006 ± 0.001). In addition, dual-element (C–H) isotope analysis of SMX was performed in the present study, which was achieved by utilizing gas chromatography (GC) as the separation method instead of routine liquid chromatography. This dual-element isotope analysis resulted in a Λ value of 4.5 ± 2.2. Overall, compound specific isotope analysis can be a feasible tool to monitor the mitigation of SMX in wastewater treatment plants.

Wide distribution of the sad gene cluster for sub-terminal oxidation in alkane utilizers.

Alkane constitutes major fractions of crude oils, and its microbial aerobic degradation dominantly follows the terminal oxidation and the sub-terminal pathways. However, the latter one received much less attention, especially since the related genes were yet to be fully defined. Here, we isolated a bacterium designated Acinetobacter sp. strain NyZ410, capable of growing on alkanes with a range of chain lengths and derived sub-terminal oxidation products. From its genome, a secondary alcohol degradation gene cluster (sad) was identified to be likely involved in converting the aliphatic secondary alcohols (the sub-terminal oxidation products of alkanes) to the corresponding primary alcohols by removing two-carbon unit. On this cluster, sadC encoded an alcohol dehydrogenase converting the aliphatic secondary alcohols to the corresponding ketones; sadD encoded a Baeyer-Villiger monooxygenase catalysing the conversion of the aliphatic ketones to the corresponding esters; SadA and SadB are two esterases hydrolyzing aliphatic esters to the primary alcohols and acetic acids. Bioinformatics analyses indicated that the sad cluster was widely distributed in the genomes of probable alkane degraders, apparently coexisting (64%) with the signature enzymes AlkM and AlmA for alkane terminal oxidation in 350 bacterial genomes. It suggests that the alkane sub-terminal oxidation may be more ubiquitous than previously thought.

Pronounced temporal changes in soil microbial community and nitrogen transformation caused by benzalkonium chloride

As one typical cationic disinfectant, quaternary ammonium compounds (QACs) were approved for surface disinfection in the coronavirus disease 2019 pandemic and then unintentionally or intentionally released into the surrounding environment. Concerningly, it is still unclear how the soil microbial community succession happens and the nitrogen (N) cycling processes alter when exposed to QACs. In this study, one common QAC (benzalkonium chloride (BAC) was selected as the target contaminant, and its effects on the temporal changes in soil microbial community structure and nitrogen transformation processes were determined by qPCR and 16S rRNA sequencing-based methods. The results showed that the aerobic microbial degradation of BAC in the two different soils followed first-order kinetics with a half-life (4.92 vs. 17.33 days) highly dependent on the properties of the soil. BAC activated the abundance of N fixation gene (nifH) and nitrification genes (AOA and AOB) in the soil and inhibited that of denitrification gene (narG). BAC exposure resulted in the decrease of the alpha diversity of soil microbial community and the enrichment of Crenarchaeota and Proteobacteria. This study demonstrates that BAC degradation is accompanied by changes in soil microbial community structure and N transformation capacity.

A global survey reveals a divergent extradiol dioxygenase clade as a widespread complementary contributor to the biodegradation of mono- and polycyclic aromatic hydrocarbons

Extradiol dioxygenation is a key reaction in the microbial aerobic degradation of mono- and polycyclic aromatic hydrocarbon catecholic derivatives. It has been reported that many bacterial enzymes exhibiting such converging functions act on a wide range of catecholic substrates. The present study reports a new subfamily of extradiol dioxygenases (EXDOs) with broad substrate specificity, the HrbC EXDOs. The new clade belongs to the XII cluster within family 2 of the vicinal oxygen chelate superfamily (EXDO-VC2), which is typically characterized by a preference for bicyclic substrates. Coding hrbC orthologs were isolated by activity-based screening of fosmid metagenomic libraries from large DNA fragments derived from heavily PAH-contaminated soils. They occurred as solitary genes within conserved sequences encoding enzymes for amino acid metabolism and were stably maintained in the chromosomes of the Betaproteobacteria lineages harboring them. Analysis of contaminated aquifers revealed coexpression of hrbC as a polycistronic mRNA component. The predicted open reading frames were verified by cloning and heterologous expression, confirming the expected molecular mass and meta-cleavage activity of the recombinant enzymes. Evolutionary analysis of the HrbC protein sequences grouped them into a discrete cluster of 1,2-dihydroxynaphthalene dioxygenases represented by a cultured PAH degrader, Rugosibacter aromaticivorans strain Ca6. The ecological importance and relevance of the new EXDO genes were confirmed by PCR-based mapping in different biogeographical localities contaminated with a variety of mono- and polycyclic aromatic compounds. The cosmopolitan distribution of hrbC in PAH-contaminated aquifers supports our hypothesis about its auxiliary role in the degradation of toxic catecholic intermediates, contributing to the composite EXDO catabolic capacity of the world's microbiomes.

Degradation of Brominated Organic Compounds (Flame Retardants) by a Four-Strain Consortium Isolated from Contaminated Groundwater

Biodegradation of pollutants in the environment is directly affected by microbial communities and pollutant mixture at the site. Lab experiments using bacterial consortia and substrate mixtures are required to increase our understanding of these processes in the environment. One of the deficiencies of working with environmental cultures is the inability to culture and identify the active strains while knowing they are representative of the original environment. In the present study, we tested the aerobic microbial degradation of two brominated flame retardants, tribromo-neopentyl alcohol (TBNPA) and dibromo neopentyl glycol (DBNPG), by an assembled bacterial consortium of four strains. The four strains were isolated and plate-cultured from a consortium enriched from the impacted groundwater underlying the Neot Hovav industrial area (Negev, Israel), in which TBNPA and DBNPG are abundant pollutants. Total degradation (3–7 days) occurred only when the four-strain consortium was incubated together (25 °C; pH −7.2) with an additional carbon source, as both compounds were not utilized as such. Bacterial growth was found to be the limiting factor. A dual carbon–bromine isotope analysis was used to corroborate the claim that the isolated strains were responsible for the degradation in the original enriched consortium, thus ensuring that the isolated four-strain microbial consortium is representative of the actual environmental enrichment.

Aerobic biodegradation of emerging azole contaminants by return activated sludge and enrichment cultures

Azoles are an emerging class of contaminants with a growing ubiquitous presence in the environment. This study investigates the aerobic microbial degradation of four azoles, pyrazole (PA), 1,2,4-triazole (TA), benzotriazole (BTA) and 5-methylbenzotriazole (5-MBTA), with return activated sludge and microbial enrichment cultures. Slow degradation of PA was observed in the presence of glucose and NH4+ with a peak degradation rate of 0.5 mg d-1 gVSS-1. TA was found to be highly persistent, with no significant degradation observed in 6–8 months under any incubation condition. In contrast, the benzotriazoles were readily degraded at faster rates in all incubation conditions. The degradation rates observed for BTA and 5-MBTA, when provided as the sole substrates, were 8.1 and 16.5 mg d-1 gVSS-1, respectively. Two enrichment cultures, one degrading BTA and the other degrading 5-MBTA, were developed from the activated sludge. Mass balance studies revealed complete mineralization of 5-MBTA and partial breakdown of BTA by the enrichment cultures. Nocardioides sp. and Pandoraea pnomenusa were the most abundant bacteria in the BTA and 5-MBTA degrading enrichment cultures, respectively. The research shows large differences in the biodegradability of various azoles, ranging from complete mineralization of 5-MBTA to complete persistence for TA.

Removal of 1,4-dioxane during on-site wastewater treatment using nitrogen removing biofilters

The presence and release of 1,4-dioxane to groundwater from onsite-wastewater treatment systems (OWTS), which represent 25% of the total wastewater treatment in the U.S., has not been studied to date. In this study we monitored 1,4-dioxane in six septic tank effluents (STE) and receiving OWTS installed at residences on Long Island (LI), NY, for a period of 15 months. We specifically evaluated the performance of Nitrogen Removing Biofilters (NRBs) as an innovative/alternative-OWTS, consisting of a top sand layer and a bottom woodchip/sand layer, to simultaneously remove nitrogen and 1,4-dioxane. 1,4-Dioxane levels in STE (mean: 1.49 μg L−1; range: 0.07–8.45 μg L−1; n = 37) were on average > 15 times higher than tap water from these residences, demonstrating that 1,4-dioxane primarily originated from the use of household products. NRBs were effective in removing both 1,4-dioxane and total nitrogen with an overall removal efficiency of 56 ± 20% and 88 ± 12%, respectively. The majority of 1,4-dioxane removal (~80%) occurred in the top oxic layer of the NRBs. The detection of functional genes (dxmB, prmA, and thmA), which encode for metabolic and co-metabolic 1,4-dioxane degradation, in NRBs provides the first field evidence of aerobic microbial degradation of 1,4-dioxane occurring in a wastewater system. Given that there are ~500,000 conventional OWTS on LI, the 1,4-dioxane discharge to groundwater from residential wastewater was estimated at 195 ± 205 kg yr −1, suggesting high risk of contamination to shallow aquifers. The results also demonstrate that installation of NRBs can reduce 1,4-dioxane to levels even lower than the NY State drinking water standard of 1 μg L−1.

Recent advances in the biodegradation of polychlorinated biphenyls.

Polychlorinated biphenyls (PCBs) are typical lasting organic pollutants. Persistence and recalcitrance to biodegradation of PCBs have hampered the transformation of PCB congeners from the environment. Biological transformation of polychlorinated biphenyls could take place through anaerobic dechlorination, aerobic microbial degradation, and a combination of transformation of anaerobic dechlorination and aerobic degradation. Under anaerobic conditions, microbial dechlorination is an important degradation mode for PCBs, especially high-chlorinated congeners. The low-chlorinated compounds formed after reductive dechlorination could be further aerobically degraded and completely mineralized. This paper reviews the recent advances in biological degradation of PCBs, introduces the functional bacteria and enzymes involved in the anaerobic and aerobic degradation of PCBs, and discusses the synergistic action of anaerobic reduction and aerobic degradation. In addition, the different ways to the microbial remediation of PCBs-contaminated environments are discussed. This review provides a theoretical foundation and practical basis to use PCBs-degrading microorganisms for bioremediation.

Behavior assessment of sulfonamides and N4-acetyl sulfonamides from wastewater effluent in subsurface constructed wetlands: Removal, distribution, and biotransformation

Wastewater treatment plant (WWTP) is the point source of antibiotic contamination, yet the removal of antibiotics from WWTP effluent has not been given necessary attention. In this study, subsurface constructed wetlands (SCWs) were used to investigate the removal, distribution, and biotransformation of sulfonamides (SAs) and their N4-acetyl sulfonamides (Ac-SAs) from wastewater effluent. The results showed that SCWs was demonstrated as capable for removing SAs with their Ac-SAs efficiently from WWTP effluent. The removal of SAs was significantly impacted by the occurrence of biotransformation behavior of SAs, not only SAs degraded into Ac-SAs, but also some Ac-SAs converted into SAs. Microbial aerobic degradation is the major removal pathway of SAs and Ac-SAs in the SCWs. SCW configuration such as vertical flow is conductive to the oxygen transport inside system and therefore promote the aerobic process of contaminants. Plants also play an important role on affecting the temporal and spatial variation of SAs through rhizosphere effect, i.e. accumulating SAs in the vegetation biomass by plant uptake and transpiration, concentrating SAs in the root zone by rhizosphere sorption and interception, and enhancing microbial influence on their aerobic decomposition by root oxygen release. The knowledge obtained in this study will be helpful for advanced purification of WWTP discharge and bioremediation of antibiotic contamination.

Anaerobic degradation of microcystin-LR by an indigenous bacterial Enterobacter sp. YF3

ABSTRACTMicrocystin-LR (MC-LR), a known hepatotoxin present in drinking water, and contaminated food and algal dietary supplements poses a threat to environmental and public health and thus needs to be removed. Previously microbial aerobic degradation was considered the predominant catabolic process for MC-LR inactivation, but the potential role of anaerobic microbes still needs to be determined. In our study an anaerobic MC-degrading bacterium Enterobacter sp. YF3 was isolated and identified that was capable of degrading MC-LR. Under optimal conditions the anaerobic Enterobacter sp. YF3 displayed a MC-degrading rate of 0.34 µg/ml/day. This process was dependent on temperature, pH and MC-LR concentration. Further the extracellular secretion of metabolites of anaerobic bacterium degraded MC-LR at 0.22 µg/ml/day. The parent MC-LR as well as two MC-degrading products was identified by high performance liquid chromatography (HPLC). The anaerobic MC-degrading Enterobacter sp. bacterium metabolized MC-LR independent of MC-degrading genes mlrABCD. Data indicate that anaerobic Enterobacter sp. YF3 produces MC-degrading products via a pathway that acts independently of mlrABCD genes which may add to the arsenal of bacteria to degrade microcystins.

Decomposition of sediment-oil-agglomerates in a Gulf of Mexico sandy beach

Sediment-oil-agglomerates (SOA) are one of the most common forms of contamination impacting shores after a major oil spill; and following the Deepwater Horizon (DWH) accident, large numbers of SOAs were buried in the sandy beaches of the northeastern Gulf of Mexico. SOAs provide a source of toxic oil compounds, and although SOAs can persist for many years, their long-term fate was unknown. Here we report the results of a 3-year in-situ experiment that quantified the degradation of standardized SOAs buried in the upper 50 cm of a North Florida sandy beach. Time series of hydrocarbon mass, carbon content, n-alkanes, PAHs, and fluorescence indicate that the decomposition of golf-ball-size DWH-SOAs embedded in beach sand takes at least 32 years, while SOA degradation without sediment contact would require more than 100 years. SOA alkane and PAH decay rates within the sediment were similar to those at the beach surface. The porous structure of the SOAs kept their cores oxygen-replete. The results reveal that SOAs buried deep in beach sands can be decomposed through relatively rapid aerobic microbial oil degradation in the tidally ventilated permeable beach sand, emphasizing the role of the sandy beach as an aerobic biocatalytical reactor at the land-ocean interface.

Characterization of phthalate reductase from Ralstonia eutropha CH34 and in silico study of phthalate dioxygenase and phthalate reductase interaction

Microbial degradation is a natural means to combat ubiquitous, harmful and non-covalently bound plasticizers, phthalic acid esters (PAEs), due to their slower photo-degradation and hydrolysis rates. In microbial aerobic degradation of phthalates, phthalate dioxygenase system (PDS) belongs to a large family of Rieske non-heme iron oxygenases with type1A electron-transfer system. Two important proteins of this system include: phthalate dioxygenase reductase (PDR), a flavo-iron-sulfur protein having NADH-dependent oxidoreductase activity; and phthalate dioxygenase oxygenase (PDO), a non-heme iron protein with oxygenase activity. In the present study, phthalate dioxygenase reductase (RePDR) from Ralstonia eutropha CH34, has been cloned, expressed and purified. Further, in order to understand the interactions between RePDO and RePDR, protein-protein docking has been carried out. The homology model structures of the individual proteins served as an input for protein-protein interaction studies and helps in the prediction of complex structure. Important interface residues from both the individual counterparts, i.e. RePDO and RePDR have been identified and the evolutionary relationship between these important interface residues has also been established. Moreover, the stability of these interactions involving highly conserved interface residues, highlights their involvement in structurally conserved interactions and play significant role in phthalate degrading system.

Natural and anthropogenic disturbances shape benthic phototrophic and heterotrophic microbial communities in the Po River Delta system

This study represents the first example in which benthic heterotrophic and photoautotrophic microbial communities (prokaryotes and microphytobenthos-MPB, respectively) were simultaneously investigated. To explore how they synergistically respond to multiple natural and anthropogenic stressors, in the framework of the Project RITMARE four lagoons of the Po River Delta were sampled in May 2016: two with more marine features, i.e. Scardovari (SC) and Caleri (CL), and two more directly affected by the Po River flow, i.e. Canarin (CN) and Vallona-Marinetta (MV). The abundance and structure of benthic communities were related to physical-chemical parameters i.e. grain-size, total N, total organic C, stable C and N isotopes, and synthetic organic contaminants. Stations were gathered into three distinct groups (Ransosim = 0.540 p < 0.001) according to their different physical-chemical features: outer, inner-freshwater and inner-marine sites. Contamination levels did not seem to severely affect the microbial abundances that were overall stimulated by the combined effect of high organic and nutrient loads: prokaryotes up to +42% and MPB up to +93%. Bacteria and Archaea displayed high densities at sites directly influenced by the freshwater input and anthropogenically derived nitrogen. Delta- (30.8%), Alpha- (12.8%), Gamma- (11.8%) and Beta-Proteobacteria (7.1%) were the dominant classes at all sites. For both communities, a significant inter-lagoonal (among different lagoons) and intra-lagoonal (among stations within the same lagoon) pattern was highlighted by PERMANOVA. nMDS and SIMPER analyses revealed distinct assemblages in the inner and outer parts of the lagoons. We applied a novel functional approach based on diatom life modes. At inner and outer sites, different diatom living forms developed: epipsammic (on sand) nearby the lagoonal mouths, epipelic (on mud) at the innermost sites and non-benthic forms (planktonic, tychopelagic and epiphytic) at sites directly influenced by freshwater. Distance-based Linear Models further indicated that salinity, clay and temperature were the significant drivers of the prokaryotic spatial distribution whereas clay, PAHs, PCBs and salinity best explained the MPB structure. The dominance of non-benthic diatom life modes in the more polluted lagoon (CN) suggests a negative influence of contamination on the MPB structure. Two diatom keystone species likely contribute to restore the oxic gradient in sediments frequently exposed to anoxia, allowing the subsequent microbial aerobic degradation and the recolonization of higher trophic organisms. The capacity of re-oxygenation after anoxia has important ecological and economic implications in lagoons exploited for aquaculture.

Degradation Kinetics and Transformation Products of Levonorgestrel and Quinestrol in Soils.

Levonorgestrel (LNG) and quinestrol (QUN) are typical endocrine disruptors that enter the soil via sewage irrigation and sludge return. However, the fates of both compounds in soil are not well-understood. Laboratory microcosm studies were conducted to fill the gap of understanding of LNG and QUN behavior in soils. High values of goodness-of-fit indices (GFIs) were obtained using the double-first-order in parallel (DFOP) model and the single-first-order (SFO) model to fit the degradation kinetics of LNG and QUN in soils, respectively. The end-points (DT50 and DT90) of LNG and QUN were positively correlated with soil total organic carbon (TOC). Soil water content and temperature were observed to be critical factors in degradation of LNG and QUN. The degradation rates of LNG and QUN were very slow under sterile and flooded conditions, indicating that the aerobic microbial degradation was dominant in the degradation of LNG and QUN. Moreover, major transformation products were identified, and biodegradation pathways of LNG and QUN were proposed. The present study is expected to provide basic information for ecological risk assessment of LNG and QUN in the soil compartment.

Chromophoric dissolved organic matter in summer in a coastal mariculture region of northern Shandong Peninsula, North Yellow Sea

Four field cruises were carried out in a mariculture region of the northern Shandong Peninsula from June to September 2017. The concentration of dissolved organic carbon (DOC) together with the absorbance and fluorescence indices of chromophoric dissolved organic matter (CDOM) were measured. The parallel factor analysis model identified four unique fluorescent components consisting of two protein components identified as tyrosine-like C1 and tryptophan-like C2, and two humic-like components C3 and C4. The DOC, CDOM absorption coefficient at 350 nm (a350) and protein-like components C1 and C2 exhibited obvious monthly variations particularly. However, the monthly variation of humic-like components C3 and C4 was not significantly different. Spatially, the a350 and fluorescent components C1-C4 were higher in the nearshore area and decreased towards the offshore area. The humification index, fluorescence index and biological index indicated the predominant autochthonous and microbial sources of CDOM. In the surface water, phytoplankton was assessed as the contributor to 11.6–35.2% of the CDOM, and 9.0–37.4%, 9.1–37.4%, 7.8–18.7% and 11.4–19.9% of the CDOM were identified as C1, C2, C3 and C4, respectively. The river inputs, especially the Xin'an River, have an important impact on DOM dynamics. In the bottom water, microbial aerobic degradation of sinking biogenic particles is an important source of humic-like components, which contributed 9.1%, 18.7% and 48.5% to C3 in July, August and September, and 14.6%, 16.3%, 18.0% and 26.6% to C4 from June to September, respectively.