Recycling Of Organic Matter Research Articles

Current and potential recycling of exogenous organic matter as fertilizers and amendments in a French peri-urban territory

Animal breeding, industries and cities produce byproducts and wastes that can be recycled in agriculture as exogenous organic matters (EOMs), promoting soil carbon storage and nutrient recycling. Peri-urban areas show a strong potential for recycling urban EOMs in agriculture. This potential needs to be better quantified in regard to farmer fertilizer demand. We investigated this question in a peri-urban territory, namely, the Versailles plain, which is located near Paris, France. We coupled interviews with farmers and waste managers with regional datasets to identify accurate flows of organic matter and their associated nutrients. The EOM potential for C storage was assessed with the AMG soil carbon model. Potentials for P, K and (short-term) N fertilizer substitutions were based on fertilizer equivalent coefficients. Additionally, we assessed the potential additional mineral N release related to increased soil organic matter after repeated EOM applications. For social and technical reasons, local EOM recycling was unequal; it was high for manures and compost and low for sewage sludge. Inputs of efficient C into soils due to EOM recycling corresponded to 20% of the inputs from crop residues. Current EOM use met 44% and 50% of the crop P and K demands, respectively. The potential for N fertilizer substitution was very low but increased when considering the additional mineral N available after long-term EOM applications. EOM could reach higher potential, especially when considering the anaerobic digestion of biowaste and potential source-separation of human urine (up to the whole P and K demand and half of N demand).

Lake thermal structure drives interannual variability in summer anoxia dynamics in a eutrophic lake over 37 years

Abstract. The concentration of oxygen is fundamental to lake water quality and ecosystem functioning through its control over habitat availability for organisms, redox reactions, and recycling of organic material. In many eutrophic lakes, oxygen depletion in the bottom layer (hypolimnion) occurs annually during summer stratification. The temporal and spatial extent of summer hypolimnetic anoxia is determined by interactions between the lake and its external drivers (e.g., catchment characteristics, nutrient loads, meteorology) as well as internal feedback mechanisms (e.g., organic matter recycling, phytoplankton blooms). How these drivers interact to control the evolution of lake anoxia over decadal timescales will determine, in part, the future lake water quality. In this study, we used a vertical one-dimensional hydrodynamic–ecological model (GLM-AED2) coupled with a calibrated hydrological catchment model (PIHM-Lake) to simulate the thermal and water quality dynamics of the eutrophic Lake Mendota (USA) over a 37 year period. The calibration and validation of the lake model consisted of a global sensitivity evaluation as well as the application of an optimization algorithm to improve the fit between observed and simulated data. We calculated stability indices (Schmidt stability, Birgean work, stored internal heat), identified spring mixing and summer stratification periods, and quantified the energy required for stratification and mixing. To qualify which external and internal factors were most important in driving the interannual variation in summer anoxia, we applied a random-forest classifier and multiple linear regressions to modeled ecosystem variables (e.g., stratification onset and offset, ice duration, gross primary production). Lake Mendota exhibited prolonged hypolimnetic anoxia each summer, lasting between 50–60 d. The summer heat budget, the timing of thermal stratification, and the gross primary production in the epilimnion prior to summer stratification were the most important predictors of the spatial and temporal extent of summer anoxia periods in Lake Mendota. Interannual variability in anoxia was largely driven by physical factors: earlier onset of thermal stratification in combination with a higher vertical stability strongly affected the duration and spatial extent of summer anoxia. A measured step change upward in summer anoxia in 2010 was unexplained by the GLM-AED2 model. Although the cause remains unknown, possible factors include invasion by the predacious zooplankton Bythotrephes longimanus. As the heat budget depended primarily on external meteorological conditions, the spatial and temporal extent of summer anoxia in Lake Mendota is likely to increase in the near future as a result of projected climate change in the region.

Insect decline: immediate action is needed.

Insects appeared more than 400 million years ago and they represent the richest and most diverse taxonomic group with several million species. Yet, under the combined effect of the loss of natural habitats, the intensification of agriculture with massive use of pesticides, global warming and biological invasions, insects show alarming signs of decline. Although difficult to quantify, species extinction and population reductions are confirmed for many ecosystems. This results in a loss of services such as the pollination of plants, including food crops, the recycling of organic matter, the supply of goods such as honey and the stability of food webs. It is therefore urgent to halt the decline of Insects. We recommend implementing long-term monitoring of populations, tackling the causes of insect decline by reducing the use of synthetic insecticides, preserving natural habitats, and reinventing a positive relationship between humans and insects.

Diversidade de mesoinvertebrados associada ao tratamento aeróbio de resíduos sólidos orgânicos domiciliares

Os mesoinvertebrados provocam mudanças nas propriedades físicas e químicas da matéria orgânica durante o processo de compostagem. São excelentes recicladores de matéria orgânica. O objetivo deste estudo foi avaliar a densidade e a diversidade de mesoinvertebrados em sistema de tratamento aeróbio de resíduos sólidos orgânicos domiciliares. O trabalho realizado em Campina Grande, estado da Paraíba, Brasil, seguiu os princípios da pesquisa experimental. Foram coletados resíduos sólidos orgânicos em 46 residências, previamente segregados na fonte geradora. Por 15 semanas o sistema foi monitorado diariamente. Durante a compostagem foram coletados 1.258 indivíduos pertencentes à seis ordens: Diptera (88,5%), Mesostigmata (5,5%), Coleoptera (2,4%), Isopoda (2,4%), Araneae (0,6%) e Orthoptera (0,6%). No processo de compostagem foram observadas três fases distintas, nas quais as espécies foram diferenciadas. Constatou-se que no sistema de tratamento dos resíduos sólidos orgânicos domiciliares, há considerável participação de organismos que atuam nas diferentes fases do tratamento, correlacionando-se com as mudanças físico-químicas e influenciando no funcionamento de todo o sistema.

Solid Waste Management Aiming Biogas Production In Albania

One of the main environmental problems in Albania is the continuously increasing generation of municipal solid waste. In many countries, sustainable waste management as well as waste prevention and reduction, have become major priority. Uncontrolled waste dumping (on the roads, river sides, etc.) in our country is no longer acceptable. Controlled landfill disposal and incineration of wastes are not considered optimal practices, as energy recovery and recycling of nutrients and organic matter is aimed. Continuously efforts have been done for the improvement of this critical situation such as approval of laws, decisions, regulations etc., according to the National Strategy on Integrated Waste Management (2018-2030) and EU Directives 2008/98/EC on waste and repealing certain Directives. In this paper are presented the characteristics of a wide range of urban solid waste, industrial solid waste and composition of the waste i.e. waste stream. As organic waste component represents the highest percentage (41% – 66%) at the waste composition should be used for biological treatment and for biogas production.

Greenhouse gases and biogeochemical diel fluctuations in a high-altitude wetland

The landscapes of high-altitude wetland ecosystems are characterized by different kinds of aquatic sites, including ponds holding conspicuous microbial life. Here, we examined a representative pond of the wetland landscape for dynamics of greenhouse gases, and their association with other relevant biogeochemical conditions including diel shifts of microbial communities' structure and activity over two consecutive days. Satellite image analysis indicates that the area of ponds cover 238 of 381.3 Ha (i.e., 62.4%), representing a significant landscape in this wetland. Solar radiation, wind velocity and temperature varied daily and between the days sampled, influencing the biogeochemical dynamics in the pond, shifting the pond reservoir of inorganic versus dissolved organic nitrogen/phosphorus bioavailability, between day 1 and day 2. Day 2 was characterized by high dissolved organic nitrogen/phosphorus and N2O accumulation. CH4 presented a positive excess showing maxima at hours of high radiation during both days. The microbial community in the sediment was diverse and enriched in keystone active groups potentially related with GHG recycling including bacteria and archaea, such as Cyanobacteria, Verrucomicrobia, Rhodobacterales and Nanoarchaeaota (Woesearchaeia). Archaea account for the microbial community composition changes between both days and for the secondary productivity in the water measured during day 2. The results indicate that an intense recycling of organic matter occurs in the pond systems and that the activity of the microbial community is correlated with the availability of nutrients. Together, the above results indicate a net sink of CO2 and N2O, which has also been reported for other natural and artificial ponds. Overall, our two-day fluctuation study in a representative pond of a high-altitude wetland aquatic landscape indicates the need to explore in more detail the short-term besides the long-term biogeochemical variability in arid ecosystems of the Andes plateau, where wetlands are hotspots of life currently under high anthropogenic pressure.

Extensive Microbial Processing of Polysaccharides in the South Pacific Gyre via Selfish Uptake and Extracellular Hydrolysis.

Primary productivity occurs throughout the deep euphotic zone of the oligotrophic South Pacific Gyre (SPG), fueled largely by the regeneration of nutrients and thus recycling of organic matter. We investigated the heterotrophic capabilities of the SPG’s bacterial communities by examining their ability to process polysaccharides, an important component of marine organic matter. We focused on the initial step of organic matter degradation by measuring the activities of extracellular enzymes that hydrolyze six different polysaccharides to smaller sizes. This process can occur by two distinct mechanisms: “selfish uptake,” in which initial hydrolysis is coupled to transport of large polysaccharide fragments into the periplasmic space of bacteria, with little to no loss of hydrolysis products to the external environment, and “external hydrolysis,” in which low molecular weight (LMW) hydrolysis products are produced in the external environment. Given the oligotrophic nature of the SPG, we did not expect high enzymatic activity; however, we found that all six polysaccharides were hydrolyzed externally and taken up selfishly in the central SPG, observations that may be linked to a comparatively high abundance of diatoms at the depth and location sampled (75 m). At the edge of the gyre and close to the center of the gyre, four of six polysaccharides were externally hydrolyzed, and a lower fraction of the bacterial community showed selfish uptake. One polysaccharide (fucoidan) was selfishly taken up without measurable external hydrolysis at two stations. Additional incubations of central gyre water from depths of 1,250 and 2,800 m with laminarin (an abundant polysaccharide in the ocean) led to extreme growth of opportunistic bacteria (Alteromonas), as tracked by cell counts and next generation sequencing of the bacterial communities. These Alteromonas appear to concurrently selfishly take up laminarin and release LMW hydrolysis products. Overall, extracellular enzyme activities in the SPG were similar to activities in non-oligotrophic regions, and a considerable fraction of the community was capable of selfish uptake at all three stations. A diverse set of bacteria responded to and are potentially important for the recycling of organic matter in the SPG.

Seasonal impact of grazing, viral mortality, resource availability and light on the group-specific growth rates of coastal Mediterranean bacterioplankton

Estimation of prokaryotic growth rates is critical to understand the ecological role and contribution of different microbes to marine biogeochemical cycles. However, there is a general lack of knowledge on what factors control the growth rates of different prokaryotic groups and how these vary between sites and along seasons at a given site. We carried out several manipulation experiments during the four astronomical seasons in the coastal NW Mediterranean in order to evaluate the impact of grazing, viral mortality, resource competition and light on the growth and loss rates of prokaryotes. Gross and net growth rates of different bacterioplankton groups targeted by group-specific CARD-FISH probes and infrared microscopy (for aerobic anoxygenic phototrophs, AAP), were calculated from changes in cell abundances. Maximal group-specific growth rates were achieved when both predation pressure and nutrient limitation were experimentally minimized, while only a minimal effect of viral pressure on growth rates was observed; nevertheless, the response to predation removal was more remarkable in winter, when the bacterial community was not subjected to nutrient limitation. Although all groups showed increases in their growth rates when resource competition as well as grazers and viral pressure were reduced, Alteromonadaceae consistently presented the highest rates in all seasons. The response to light availability was generally weaker than that to the other factors, but it was variable between seasons. In summer and spring, the growth rates of AAP were stimulated by light whereas the growth of the SAR11 clade (likely containing proteorhodopsin) was enhanced by light in all seasons. Overall, our results set thresholds on bacterioplankton group-specific growth and mortality rates and contribute to estimate the seasonally changing contribution of various bacterioplankton groups to the function of microbial communities. Our results also indicate that the least abundant groups display the highest growth rates, contributing to the recycling of organic matter to a much greater extent than what their abundances alone would predict.

Inactivation and Site-specific Oxidation of Aquatic Extracellular Bacterial Leucine Aminopeptidase by Singlet Oxygen.

Extracellular enzymes are master recyclers of organic matter, and to predict their functional lifetime, we need to understand their environmental transformation processes. In surface waters, direct and indirect photochemical transformation is a known driver of inactivation. We investigated molecular changes that occur along with inactivation in aminopeptidase, an abundant class of extracellular enzymes. We studied the inactivation kinetics and localized oxidation caused by singlet oxygen, 1O2, a major photochemically derived oxidant toward amino acids. Aminopeptidase showed second-order inactivation rate constants with 1O2 comparable to those of free amino acids. We then visualized site-specific oxidation kinetics within the three-dimensional protein and demonstrated that fastest oxidation occurred around the active site and at other reactive amino acids. However, second-order oxidation rate constants did not correlate strictly with the 1O2-accessible surface areas of those amino acids. We inspected site-specific processes by a comprehensive suspect screening for 723,288 possible transformation products. We concluded that histidine involved in zinc coordination at the active site reacted slower than what was expected by its accessibility, and we differentiated between two competing reaction pathways of 1O2 with tryptophan residues. This systematic analysis can be directly applied to other proteins and transformation reactions.

Fungi and viruses as important players in microbial mats.

Microbial mats are compacted, surface-associated microbial ecosystems reminiscent of the first living communities on early Earth. While often considered predominantly prokaryotic, recent findings show that both fungi and viruses are ubiquitous in microbial mats, albeit their functional roles remain unknown. Fungal research has mostly focused on terrestrial and freshwater ecosystems where fungi are known as important recyclers of organic matter, whereas viruses are exceptionally abundant and important in aquatic ecosystems. Here, viruses have shown to affect organic matter cycling and the diversity of microbial communities by facilitating horizontal gene transfer and cell lysis. We hypothesise fungi and viruses to have similar roles in microbial mats. Based on the analysis of previous research in terrestrial and aquatic ecosystems, we outline novel hypotheses proposing strong impacts of fungi and viruses on element cycling, food web structure and function in microbial mats, and outline experimental approaches for studies needed to understand these interactions.

Chronic insect herbivores accelerate litter decomposition and nutrient recycling rates along an environmental/herbivory gradient in northern Patagonia

Canopy insects are the main consumers in forests, and understanding their ecological role includes considering their effects on litter decomposition and nutrient cycling. We experimentally evaluated how litter decomposition is shaped by the decomposition environment and by litter traits shaped by forest moisture origin and chronic insect activity. We selected 4 forest stands at the driest and wettest extremes of beech (Nothofagus pumilio) forests in northwest Patagonia (mean annual rainfall 800 and 3000 mm yr−1 respectively). In two stands from each extreme, we performed three litterbag decomposition experiments. Experiment 1 included a reciprocal litter transplant between dry and wet stands, replicated in 2 different years for 24 and 12 months. Litterbags comprised the “Natural” proportion of undamaged and damaged leaves from the local insect community. Experiments 2 and 3 examined leaf insect damage effects on litter decomposition, respectively “in situ” and under controlled conditions. Here, we included three types of litterbags: 1- “Natural” (described above), 2- only insect-damaged litter, and 3- only healthy (undamaged) litter. Reciprocal transplants showed that litter decomposition was mostly controlled by litter origin and less by the decomposition environment (wet or dry forests). But, challenging predictions based on litter quality produced under water limiting environments, “Natural” litter chemical quality did not differ between forests. Even, when compared under the same decomposition environment (wet or dry forest), “Natural” litter from dry forests decomposed 31% faster and released 109% more N than “Natural” litter from wet forests. “Natural” litter from dry forests had a higher herbivory frequency and higher dominance of endophagous insects than wet stands. The high proportion of damaged litter in dry forests decreased “Natural” litter C:N ratio to match the chemical quality of “Natural” litter from wet forests. Experiment 2 showed that, in both wet and dry forests, damaged litter decomposed 31% faster than undamaged litter (in situ). Insect damage also reduced 90% N retention, but only in dry forests. Our results suggest that differences in insect communities living in contrasting environments could act as key drivers in shaping the recycling of organic matter, counteracting environmental differences between forests.

Influence of Algal Production and Decomposition on the Carbon Isotope Signature of Labile Particulate Organic Matter on a Productive Continental Shelf Under the Stress of Coastal Hypoxia

To better understand the sources and recycling of labile organic matter in coastal water, we studied the carbon isotope signature of particulate organic carbon (POC) and particulate amino acids, a major group of labile organic compounds, on the shelf of the northern South China Sea. In addition, we were able to compare effects of hypoxia on labile organic matter at one station on the shelf. We found that carbon-weighted average d13C values of particulate amino acids (wAAd13C) were generally higher at more productive offshore stations than nearshore stations. This amino acid d13C distribution suggests that the labile fraction of organic matter in coastal water originated primarily from local primary production. In contrast, bulk POC d13C values showed little spatial variation on the NSCS shelf. The different patterns of wAAd13C and PO13C distributions indicate a combined effect of POM lability and physical processes on the isotopic distribution of organic materials on this productive shelf. Moreover, the amino acid d13C in coastal hypoxic water suggests local primary production as the most likely source of labile organic matter that drives hypoxia on the NSCS shelf. No clear difference was observed in particulate amino acid d13C distribution between hypoxic and oxic waters,

Meta-omics highlights the diversity, activity and adaptations of fungi in deep oceanic crust.

The lithified oceanic crust, lower crust gabbros in particular, has remained largely unexplored by microbiologists. Recently, evidence for heterogeneously distributed viable and transcriptionally active autotrophic and heterotrophic microbial populations within low-biomass communities was found down to 750 m below the seafloor at the Atlantis Bank Gabbro Massif, Indian Ocean. Here, we report on the diversity, activity and adaptations of fungal communities in the deep oceanic crust from ~10 to 780 mbsf by combining metabarcoding analyses with mid/high-throughput culturing approaches. Metabarcoding along with culturing indicate a low diversity of viable fungi, mostly affiliated to ubiquitous (terrestrial and aquatic environments) taxa. Ecophysiological analyses coupled with metatranscriptomics point to viable and transcriptionally active fungal populations engaged in cell division, translation, protein modifications and other vital cellular processes. Transcript data suggest possible adaptations for surviving in the nutrient-poor, lithified deep biosphere that include the recycling of organic matter. These active communities appear strongly influenced by the presence of cracks and veins in the rocks where fluids and resulting rock alteration create micro-niches.

Characterization of microbial populations associated with different organic fertilizers

Purpose Bacterial and fungal communities represent key bioindicators of soil quality and are essential for the maintenance of nutrient availability. Our purpose was to characterize the bacterial and fungal biodiversity associated with different compost mixtures, comparing microbiological indicators regarding the soil quality. Methods Compost samples and mixtures were prepared (15:1 final ratio) with chemical fertilizer, animal manures (bovine, swine, and poultry) and green waste (such as tomato waste and leaves). Bacterial and fungal isolation and identification were performed through standard phenotypic methods. Statistical methods to assess differences between treatments included Shannon diversity, Chi-square tests, Bray-Curtis clustering, and Canonical Correspondence Analysis. Results Streptomyces species, Gram-positive bacteria, were commonly found in differing abundances in all samples. Gram-positive species were predominant in soils amended with vegetable green waste while Gram-negative bacteria were more abundant in samples with chemical fertilizer. Fungal abundance increased in poultry manure and chemical fertilizers. Conclusion Our findings suggested that organic matter recycling and composting resulted in the shifting of biodiversity in bacterial and fungal populations which might be associated with the availability of certain nutrient sources provided by the composting materials.

Conceptual Models of Gas Accumulation in the Shallow Permafrost of Northern West Siberia and Conditions for Explosive Gas Emissions

Gas accumulation and pressurized unfrozen rocks under lakes (sublake taliks) subject to freezing in shallow permafrost may lead to explosive gas emissions and the formation of craters. Gas inputs into taliks may have several sources: microbially-mediated recycling of organic matter, dissociation of intrapermafrost gas hydrates, and migration of subpermafrost and deep gases through permeable zones in a deformed crust. The cryogenic concentration of gas increases the pore pressure in the freezing gas-saturated talik. The gradual pressure buildup within the confined talik causes creep (ductile) deformation of the overlying permafrost and produces a mound on the surface. As the pore pressure in the freezing talik surpasses the permafrost strength, the gas-water-soil mixture of the talik erupts explosively and a crater forms where the mound was. The critical pressure in the confined gas-saturated talik (2–2.5 MPa for methane) corresponds to the onset of gas hydrate formation. The conditions of gas accumulation and excess pressure in freezing closed taliks in shallow permafrost, which may be responsible for explosive gas emissions and the formation of craters, are described by several models.

Pollination by hoverflies in the Anthropocene.

Pollinator declines, changes in land use and climate-induced shifts in phenology have the potential to seriously affect ecosystem function and food security by disrupting pollination services provided by insects. Much of the current research focuses on bees, or groups other insects together as ‘non-bee pollinators’, obscuring the relative contribution of this diverse group of organisms. Prominent among the ‘non-bee pollinators’ are the hoverflies, known to visit at least 72% of global food crops, which we estimate to be worth around US$300 billion per year, together with over 70% of animal pollinated wildflowers. In addition, hoverflies provide ecosystem functions not seen in bees, such as crop protection from pests, recycling of organic matter and long-distance pollen transfer. Migratory species, in particular, can be hugely abundant and unlike many insect pollinators, do not yet appear to be in serious decline. In this review, we contrast the roles of hoverflies and bees as pollinators, discuss the need for research and monitoring of different pollinator responses to anthropogenic change and examine emerging research into large populations of migratory hoverflies, the threats they face and how they might be used to improve sustainable agriculture.

Lake Martin, Louisiana sediments as a record of geomorphology, paleoenvironment, and human activities

There are relatively few lake sediment records from the southeastern United States that span sufficient time to characterize the environment prior to substantial anthropogenic disturbance. This has made it difficult to characterize the magnitude and timing of the impact of industrial human activities within the context of natural variability. The objective of this study was therefore to use weight percent organic matter, carbon to nitrogen ratios, carbon and nitrogen isotopes, and weakly bound lead concentrations from Lake Martin, a small oxbow lake in southern Louisiana, to (1) characterize natural variability in lake carbon and nitrogen cycling within the last several millennia in a vastly understudied region of the US and (2) assess the impact of recent human activities such as agriculture, land-use change, and industrial activities on the water and sediment quality of the lake. The basal sediments from Lake Martin are distinctive in color and character and likely derive from a large paleo-lake that catastrophically drained in the late Holocene. The last 1100 years of the record demonstrates a gradual transition from a system with moderate amounts of terrestrial materials to one dominated by aquatic organic matter likely due to the transition from a lotic to lentic system. Coincident with when the Acadians settled in the Lafayette area around 200 years ago, further changes are apparent in the sediment record, but do not display the hallmark signs of either land-use change or cultural eutrophication. This may be because lake levels are low and led to the efficient oxidation and recycling of organic matter.

What factors influence the occurrence of Cubitermes pallidiceps in miombo woodlands in southwestern Burundi?

In Africa, not only large number of termite species remain to be described, but also ecological studies on the termite fauna of the continent are scarce. For instance, the mechanisms underlying termite mounds distribution in ecosystems stay poorly known. The main goal of this study was to assess what determines the distribution of soil-feeding termites playing an important role in the recycling of organic matter. The case of Cubitermes pallidiceps (Sjöstedt) (Isoptera: Cubitermitinae) was taken as a model. In Rumonge Forest, a woodland miombo of 600 ha in southwestern Burundi, we collected soil samples and data on tree density and diameter in 18 sites, six of which were home to mounds of C. pallidiceps. Multiple logistic regressions were used to evaluate the influence of soil properties and elevation on the occurrence of C. pallidiceps. Spatial autocorrelation structure in the model residuals was corrected by the integration of selected spatial predictors generated with the Moran’s eigenvectors maps (MEM) method. C. pallidiceps was present in areas where the tree density was low, therefore with a more opened canopy, probably to avoid fires. Those areas would also provide it a favourable microclimate through direct solar radiation. It was absent in stony places such as hill tops, probably because of food limitation. Soil with high sand content and the highest measured clay content seemed to favour Cubitermes occurrence. Its distribution was also influenced by undetermined spatially structured variables, which could correspond to unmeasured environmental variables such as soil nutrient or toxic elements, or variables related to dispersal abilities or biotic interactions with other species. Our results suggested that soil termites would have evolved in miombo ecosystems to avoid areas with a high physiological and physical cost. Understanding ecological adaptation of soil termites in this stressful environment is important for restoration and management of their habitats.

Recovery of organic carbon from municipal mixed waste compost for the production of fertilizers

Nowadays, the extensive use of inorganic fertilizers has increased the salinity of soil and decreased optimal assimilation of nutrients by crops. Organic carbon is basic for controlling the nutrient level in soil and nutrient assimilation by plants. The objective of this study was to develop a process for recovering organic carbon using compost from mixed municipal waste as raw material. The use of fertilizers from organic residues could replace mineral fertilizers, contributing to resources preservation and recycling of organic matter. In this way, a Taguchi experimental design was proposed to select the most suitable operating conditions for recovering organic carbon from the organic residue. The variable factors were the solid:liquid ratio, type of solvent, extraction time, and particle size. The optimum extraction conditions were: solid:liquid ratio 1:2.5, 1 M potassium hydroxide (KOH), 72 h, and particle size > 1 mm. Subsequent experiments concluded that separating the mixed municipal waste compost (MMWC) by fractions of different particle sizes before extraction process is not recommended. Under these conditions, the total organic carbon concentration in the extract was 6.9% w/w, of which the content of humic acids was 47.6%. On the other hand, the extract complies with the legal requirements of Regulation (EU) 2019/1009 for fertilizing products regarding composition. Germination tests were carried out to analyze the phytotoxic effects of organic extracts. Finally, a preliminary economic study showed the viability for a production plant with a capacity of 300 kg/h of MMWC. The production of liquid fertilizer was 200 L per 100 kg of dry compost, and the estimated sale price to obtain economic benefits was 1 €/L of fertilizer for a plant whose total investment cost was 1,600 k€.

Cryptic species in the parasitic Amoebophrya species complex revealed by a polyphasic approach

As critical primary producers and recyclers of organic matter, the diversity of marine protists has been extensively explored by high-throughput barcode sequencing. However, classification of short metabarcoding sequences into traditional taxonomic units is not trivial, especially for lineages mainly known by their genetic fingerprints. This is the case for the widespread Amoebophrya ceratii species complex, parasites of their dinoflagellate congeners. We used genetic and phenotypic characters, applied to 119 Amoebophrya individuals sampled from the same geographic area, to construct practical guidelines for species delineation that could be applied in DNA/RNA based diversity analyses. Based on the internal transcribed spacer (ITS) regions, ITS2 compensatory base changes (CBC) and genome k-mer comparisons, we unambiguously defined eight cryptic species among closely related ribotypes that differed by less than 97% sequence identity in their SSU rDNA. We then followed the genetic signatures of these parasitic species during a three-year survey of Alexandrium minutum blooms. We showed that these cryptic Amoebophrya species co-occurred and shared the same ecological niche. We also observed a maximal ecological fitness for parasites having narrow to intermediate host ranges, reflecting a high cost for infecting a broader host range. This study suggests that a complete taxonomic revision of these parasitic dinoflagellates is long overdue to understand their diversity and ecological role in the marine plankton.