Particulate Organic Matter Research Articles

Soil nutrients and pH modulate carbon dynamics in particulate and mineral-associated organic matter during restoration of a Tibetan alpine grassland

Soil nutrients and pH modulate carbon dynamics in particulate and mineral-associated organic matter during restoration of a Tibetan alpine grassland

Integrated Analysis of Indoor Air Quality and Fungal Microbiota in Educational Heritage Buildings: Implications for Health and Sustainability

Indoor air quality is paramount for the health and well-being of individuals, especially in enclosed spaces like office buildings, schools, hospitals, and homes where people spend a significant amount of time. Ensuring good indoor air quality is not only essential for reducing symptoms such as headaches, eye and respiratory irritation, fatigue, and difficulty in concentration, but it is also a key component of sustainable building practices aimed at promoting long-term health and environmental balance. This study aims to explore the impact of the microclimate and fungal microbiota on the health and cognitive performance of occupants in a university classroom, which is part of a cultural heritage building. The research delves into various microclimatic parameters, including temperature, relative humidity, CO2, volatile organic compounds, O2, and particulate matters (PM2.5 and PM10), to understand their influence on the development of microbiota and the manifestation of symptoms associated with Sick Building Syndrome. Over the course of a year-long investigation, microbiological samples were collected, revealing the presence of 19 fungal species, with Cladosporium, Alternaria, and Aureobasidium being the most prevalent genera. These species were found to thrive in an environment characterized by inadequate ventilation, posing potential health risks to occupants, such as allergic reactions and respiratory infections. Microclimatic parameter values such as mean temperature of 22.9 °C and mean relative humidity of 38.5% indicated moderate conditions for fungal proliferation, but occasional high levels of PM2.5 and CO2 indicated periods of poor indoor air quality, negatively influencing the comfort and health of the occupants. The questionnaires completed by 190 students showed that 51.5% reported headaches, 44.2% frequent sneezing, and 43.7% severe fatigue, linking these symptoms to increased levels of CO2 and PM2.5. The novelty of the study lies in the integrated approach to indoor air quality assessment in a heritage educational building, highlighting the need for improved ventilation and air management to enhance health and cognitive performance, while emphasizing sustainable indoor environment management that balances occupant well-being with the preservation of cultural heritage.

Effects of Low-Severity Fire on the Composition and Stability of Soil Organic Carbon in Permafrost Peatlands (Northeast China).

Climate change and human activity are increasing the frequency of wildfires in peatlands and threatening permafrost peatland carbon pools. In Northeast China, low-severity prescribed fires are conducted annually on permafrost peatlands to reduce the risk of wildfires. These fires typically do not burn surface peat but lead to the loss of surface vegetation and introduction of pyrogenic carbon. However, the long-term effects of repeated low-severity fires on soil carbon stability in these ecosystems remain unclear. Thus, we conducted low-severity prescribed fire experiments over 3 years in the permafrost peatlands of the Great Khingan Mountains. Our findings showed a gradual decline in the total carbon content, primarily due to the reduction in free particulate organic matter (fPOM). Initially, fPOM was higher in the burned sites but decreased with repeated burning. Chemical analyses revealed a 32% increase in the aromaticity of the fPOM at the burned sites, which diminished the thermal stability of the soil. Furthermore, both prescribed fires and the addition of pyrogenic carbon reduced biological stability while increasing enzyme activity and CO2 production, which was attributed to the introduction of post-fire pyrogenic carbon. These results suggest that low-severity fires compromise the stability of permafrost peatlands, particularly because the pyrogenic carbon input alters the chemical composition of the soil carbon fraction.

Physical drivers of bio-optical properties in the Guangdong-Hong Kong-Macao Greater Bay Area during the winter dry season

Understanding the variability of bio-optical properties in coastal seas is essential to assessing the impact of natural and anthropogenic activities on the quality of the coastal environments and their resources. This study investigated the vertical distribution of bio-optical properties and their potential driving forces in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) using a bio-optical dataset collected during the winter dry season. The hydrographic and biogeochemical properties observed across the GBA exhibited significant spatial variability, allowing the classification of the waters into three distinct regions: estuarine diluted water (EDW), Guangdong coastal current water (GCCW), and dense shelf water (DSW). Our findings show that EDW exhibited beam attenuation and optical backscatter coefficients an order of magnitude greater compared to the other two regions, which was attributed to factors such as higher concentrations of suspended particulate matter and organic material from estuarine sources. In contrast, the GCCW was characterized by lower salinity, temperature, and suspended particulate matter and displayed reduced turbidity near the coast, whereas nutrient-rich GCCW waters transported to the mid-shelf region supported increased phytoplankton biomass and a greater abundance of micro-phytoplankton. By exploring the bio-optical characteristics and their underlying processes in the GBA, this study enhances our understanding of the complex dynamics shaping the optical properties of coastal waters in this heavily urbanized region.

Temperate grassland conversion to conifer forest destabilises mineral soil carbon stocks.

Tree-planting is increasingly presented as a cost-effective strategy to maximise ecosystem carbon (C) storage and thus mitigate climate change. Its success largely depends on the associated response of soil C stocks, where most terrestrial C is stored. Yet, we lack a precise understanding of how soil C stocks develop following tree planting, and particularly how it affects the form in which soil C is stored and its associated stability and resistance to climate change. Here, we present changes in C and nitrogen (N) stored as mineral-associated organic matter (OM), occluded particulate OM, free particulate OM and dissolved OM, from four regional chronosequences of Scots pine (Pinus sylvestris L.) forests planted on former grasslands across Scotland. We found that c. 58-68 years after the plantation, bulk soil C and N stocks in the organic layer and the top 20cm of mineral soil decreased by half relative to unforested grasslands - a decrease roughly equivalent to a third of the simultaneous C gain in the tree biomass. This pattern was driven predominantly by a decrease in the amount of C and N stored as mineral-associated OM, an OM fraction considered as relatively long-lived. Our findings demonstrate the need to estimate C storage in response to tree planting based both on soil C stocks and tree biomass, as the use of the latter alone may significantly over-estimate net C benefits of tree planting on permanent grasslands.

Gene content of seawater microbes is a strong predictor of water chemistry across the Great Barrier Reef

BackgroundSeawater microbes (bacteria and archaea) play essential roles in coral reefs by facilitating nutrient cycling, energy transfer, and overall reef ecosystem functioning. However, environmental disturbances such as degraded water quality and marine heatwaves, can impact these vital functions as seawater microbial communities experience notable shifts in composition and function when exposed to stressors. This sensitivity highlights the potential of seawater microbes to be used as indicators of reef health. Microbial indicator analysis has centered around measuring the taxonomic composition of seawater microbial communities, but this can obscure heterogeneity of gene content between taxonomically similar microbes, and thus, microbial functional genes have been hypothesized to have more scope for predictive potential, though empirical validation for this hypothesis is still pending. Using a metagenomics study framework, we establish a functional baseline of seawater microbiomes across offshore Great Barrier Reef (GBR) sites to compare the diagnostic value between taxonomic and functional information in inferring continuous physico-chemical metrics in the surrounding reef.ResultsIntegrating gene-centric metagenomics analyses with 17 physico-chemical variables (temperature, salinity, and particulate and dissolved nutrients) across 48 reefs revealed that associations between microbial functions and environmental parameters were twice as stable compared to taxonomy-environment associations. Distinct seasonal variations in surface water chemistry were observed, with nutrient concentrations up to threefold higher during austral summer, explained by enhanced production of particulate organic matter (POM) by photoautotrophic picocyanobacteria, primarily Synechococcus. In contrast, nutrient levels were lower in winter, and POM production was also attributed to Prochlorococcus. Additionally, heterotrophic microbes (e.g., Rhodospirillaceae, Burkholderiaceae, Flavobacteriaceae, and Rhodobacteraceae) were enriched in reefs with elevated dissolved organic carbon (DOC) and phytoplankton-derived POM, encoding functional genes related to membrane transport, sugar utilization, and energy metabolism. These microbes likely contribute to the coral reef microbial loop by capturing and recycling nutrients derived from Synechococcus and Prochlorococcus, ultimately transferring nutrients from picocyanobacterial primary producers to higher trophic levels.ConclusionThis study reveals that functional information in reef-associated seawater microbes more robustly associates with physico-chemical variables than taxonomic data, highlighting the importance of incorporating microbial function in reef monitoring initiatives. Our integrative approach to mine for stable seawater microbial biomarkers can be expanded to include additional continuous metrics of reef health (e.g., benthic cover of corals and macroalgae, fish counts/biomass) and may be applicable to other large-scale reef metagenomics datasets beyond the GBR.D4ZFkyo-_x3xtsAViMg6HSVideo

Time and climate roles in driving soil carbon distribution and stability in particulate and mineral-associated organic matter pools.

Understanding the accumulation and stability of soil organic matter (SOM) pools as a function of time (i.e., soil age) and climate (i.e., precipitation and temperature) represents a crucial challenge. This study aims at investigating the effect of both climate and time on SOM distribution into particulate and mineral-associated organic matter (POM and MAOM, respectively), using two chronosequences located along a climate gradient. The contribution of POM and MAOM to soil organic carbon (SOC) storage differs between the climo-chronosequences and with depth. The ratio between MAOM and POM pools (MAOM/POM) ranges from 0.9 to 2.0 and from 1.4 to 3.5 in the wetter and cooler and in the drier and warmer chronosequence, respectively. Regardless of the chronosequence, the MAOM/POM ratio increases with depth, highlighting a more important role of the mineral-associated fraction in carbon storage in deeper soils. The concentration of organic carbon in mineral-associated (MAOC) and particulate (POC) pools along the soil profile in the wetter and cooler chronosequence is 2× and 3× higher, respectively, than in soils from the drier and warmer one. In particular, in the wetter and cooler chronosequence, MAOC and POC concentrations decrease with soil age. In the drier and warmer chronosequence, only POC concentration decreases with soil age, whereas MAOC concentration generally increases. The thermal stability of the MAOM fraction increases with soil age and depth only in the drier and warmer climatic conditions, whereas no differences with depth occur in the wetter and cooler chronosequence. Furthermore, the MAOM energy density decreases with soil depth and age in both chronosequences. Independently of the chronosequence, POM represents the most labile pool with higher energy density. In conclusion, time and climate play a different role in SOC distribution between the pools and on their relative stability. Soil age drives MAOM stability in drier and warmer conditions, whereas a wetter and cooler climate determines a higher SOC accumulation in both pools, although these greater carbon stocks are negatively correlated with their stability.

Differential use of multiple food sources at a bathyal benthic ecosystem in the central Sagami Bay revealed by amino acid nitrogen isotopic compositions

The nitrogen isotopic composition (δ15N) of amino acids can be used to estimate the trophic position of organisms with high precision compared to bulk tissue analyses, and shed light on potential food sources and food webs. Sagami Bay, Japan, is located at the tectonic plate boundary and have complex bottom topography, making multiple sources of organic matter to bathyal deep-sea ecosystems. Here, we applied this method to benthic animals (meiofauna, macrofauna, and megafauna) living at 1430 m deep in the central Sagami Bay, Japan. The δ15N value of phenylalanine (δ15NPhe) reflects the value of primary producers and was used to estimate the food sources of organisms, while the difference between δ15N value of glutamic acid (δ15NGlu) and δ15NPhe shifts between food source and consumer and was thus used to estimate the trophic position (TPGlu/Phe). The data obtained were interpreted together with previously reported values from benthic foraminifera of the same site for a holistic understanding of the food web. The trophic positions of organisms from the central Sagami Bay ranged mostly from 2.2 to 3.6, except hydrozoans (up to 4.3). Organisms with similar bulk tissue δ15N values sometimes exhibited different TPGlu/Phe values. The observed δ15NPhe varied greatly among benthic organisms in the central Sagami Bay (− 8.3‰ to 21.1‰), suggesting a wide variety of food sources exhibiting different δ15NPhe values. Given the location of the study site at the central part of the deep basin, various organic matter from terrestrial, planktic, coastal, upper bathyal, and perhaps chemosynthetic origins can be expected to accumulate and become available for bathyal benthic organisms. Furthermore, the cross-plot of δ15NPhe values and bulk tissue δ13C values, another indicator of food source, suggested that macro–megafauna examined rely on different organic matter than metazoan meiofauna and foraminifera, which rely on particulate organic matter and bulk sediments. Despite living in the same habitat, organisms of these two size classes may belong to independent food webs due to differences in feeding ecology.

Particle composition-based water classification method for estimating chlorophyll-a in coastal waters from OLCI images

The complex composition of seawater presents significant challenges for accurately estimating biogeochemical data through optical measurements, both in situ and via satellite data. To address the regional applicability of single bio-optical or remote sensing algorithms caused by these challenges, we explored a water optical classification method based on inherent optical properties and particle composition. The ratio of organic particulate matter to total suspended particulate matter concentration (POM/SPM) serves as an optical discriminator of water bodies based on the proportions of organic and mineral particles. The boundary value is determined by the relationship between the particulate backscattering coefficient bbp(λ) and POM/SPM. By analyzing in situ data collected from the coastal waters of Qinhuangdao in the Bohai Sea, China, we developed empirical algorithms to estimate both the POM/SPM ratio and chlorophyll-a (Chl-a) concentration, the latter being a key parameter derived from current ocean remote sensing that indicates phytoplankton abundance. The evaluation of our algorithms demonstrates that accounting for POM/SPM variations significantly improves Chl-a estimate accuracy across the optically-complex coastal waters near Qinhuangdao compared to algorithms that do not consider changes in particle composition, such as the well-known OC4Me algorithm. Furthermore, we determined the distribution of monthly averaged Chl-a concentration and POM/SPM ratio on the coast of Qinhuangdao, Bohai Sea, in 2023. Our results show, for the first time, that the monthly average variations of the POM/SPM ratio in the Bohai Sea and Chl-a concentrations exhibit pronounced seasonal fluctuations.

Fatty Acids in Cnidaria: Distribution and Specific Functions.

The phylum Cnidaria comprises five main classes-Hydrozoa, Scyphozoa, Hexacorallia, Octocorallia and Cubozoa-that include such widely distributed and well-known animals as hard and soft corals, sea anemones, sea pens, gorgonians, hydroids, and jellyfish. Cnidarians play a very important role in marine ecosystems. The composition of their fatty acids (FAs) depends on food (plankton and particulate organic matter), symbiotic photosynthetic dinoflagellates and bacteria, and de novo biosynthesis in host tissues. In cnidarian lipids, besides the common FA characteristics of marine organisms, numerous new and rare FAs are also found. All Octocorallia species and some Scyphozoa jellyfish contain polyunsaturated FAs (PUFAs) with 24 and 26 carbon atoms. The coral families can be distinguished by specific FA profiles: the presence of uncommon FAs or high/low levels of common fatty acids. Many of the families have characteristic FAs: Acroporidae are characterized by 18:3n6, eicosapentaenoic acid (EPA) 20:5n3, 22:4n6, and 22:5n3; Pocilloporidae by 20:3n6, 20:4n3, and docosahexaenoic acid 22:6n3 (DHA); and Poritidae by arachidonic acid (AA) and DHA. The species of Faviidae show elevated concentrations of 18:3n6 and 22:5n3 acids. Dendrophylliidae, being azooxanthellate corals, have such dominant acids as EPA and 22:5n3 and a low content of DHA, which is the major PUFA in hermatypic corals. The major and characteristic PUFAs for Milleporidae (class Hydrozoa) are DHA and 22:5n6, though in scleractinian corals, the latter acid is found only in trace amounts.

Interseeding cover crop into an irrigated sandy loam for 6 years: Soil, crop, and economic response

AbstractInterseeding cover crops (CCs) may be a potential strategy to manage sandy soils, which are highly prone to degradation. However, how this practice affects CC biomass production and other ecosystem services in sandy soils over the traditional CC planting system (post‐harvest drilling) is still unclear. We studied how broadcast interseeded (32–67 days before crop harvest) winter rye (Secale cereale L.) CC affected CC biomass production, nitrate leaching potential, soil properties, crop yields, and farm income compared with post‐harvest drilled CC in an on‐farm irrigated no‐till corn (Zea mays L.)–soybean (Glycine max L.) experiment in a sandy loam in the western US Corn Belt for 6 years. Across the 6 years, interseeded CC produced 0.57 Mg ha−1 of biomass, while post‐harvest drilled CC produced 0.37 Mg ha−1. Nitrate leaching is a concern in sandy soils, but interseeded CC had mixed effects on soil nitrate concentration. Interseeded CC did not affect soil properties (particulate organic matter and organic C concentrations, and wet aggregate stability) and crop yields. Further, interseeded CC did not reduce farm income more than post‐harvest drilled CC. The limited effect of interseeded CCs is likely due to the relatively small increase in CC biomass production over the traditional CC planting system. Additional strategies including irrigation, drill interseeding, and planting green may boost interseeded CC biomass production and thus soil services in sandy soils. After 6 years, interseeded CC slightly boosted CC biomass production but minimally affected soils and crops, and both interseeded and post‐harvest‐drilled CCs reduced net income.

Using δ15N of Amino Acids and Nitrate to Investigate Particle Production and Transformation in the Ocean: A Case Study From the Eastern Tropical North Pacific Oxygen Deficient Zone

AbstractThe eastern tropical North Pacific oxygen deficient zone (ETNP‐ODZ) exhibits a distinct physical and biological environment compared to other oxygenated water columns, leading to a unique scenario of particulate organic matter (POM) production and vertical transport. To elucidate these biological pump processes, we present the first comparison of δ15N values of nitrate, phenylalanine (Phe), and glutamic acid (Glu) within two distinct size fractions of particles collected along a productivity gradient in the ETNP‐ODZ. Low δ15NPhe and δ15NGlu values in both particle pools at sites with prominent secondary chlorophyll maximum (SCM), compared to the ambient δ15N‐NO3−, suggest the presence of recycled N‐utilizing primary producers distinct from those at the primary chlorophyll maximum and their contribution to export. We observed reduced 15N enrichment of Phe in small particles and a narrower δ15NPhe disparity between the two particle size fractions compared to the results from oxic waters, likely due to slower heterotrophic microbial degradation of small particles. Unique δ15NPhe and δ15NGlu signatures of particles were found at the lower oxycline, potentially attributable to chemoautotrophic production and zooplankton mediation. These findings underscore the need for further investigations targeting particles generated at the SCM, their subsequent alteration by zooplankton, and the new production by chemoautotrophs. This will allow for a better evaluation of the efficiency of the biological pump in the globally expanding ODZs under contemporary climate change.

Fish Sludge as Feed in Circular Bioproduction: Overview of Biological and Chemical Hazards in Fish Sludge and Their Potential Fate via Ingestion by Invertebrates

ABSTRACTAquaculture farming discharges large volumes of fish sludge, consisting of particulate organic matter from feed spill and feces. Fish sludge from land‐based salmonid aquaculture systems can potentially be used to feed low‐trophic species such as marine polychaetes and insects. Further use of these invertebrates as feed may provide a more sustainable feed chain. However, food security must not compromise feed or food safety. The use of fish sludge as feed is currently not permitted in the European Union (EU). A regulatory assessment that considers the integration of fish sludge in the circular bioeconomy requires knowledge of the potential chemical and biological risks involved. This review has compiled data from existing literature on the occurrence of chemical and biological hazards, as well as the physical properties of fish sludge. The potential risks along this feed chain, from fish sludge to novel feed ingredient production, are discussed in light of the EU regulatory framework. Within the available, but scarce, literature on biological hazards in fish sludge, there is no clear evidence that fish sludge is unsafe for use as a feed material for invertebrates if treatment criteria established in the EU regulations are followed. Scarcity implies a level of uncertainty, but not necessary of risk. For the chemical hazards, some elements are of concern and may exceed regulatory limits, and there are limited data on the occurrence of organic pollutants. This review highlights considerable knowledge gaps concerning the use of fish sludge in a circular feed and food system.

Vertical biochemical composition of particulate organic matter in the Seychelles-Chagos Thermocline Ridge (SCTR), southwestern Indian Ocean

Vertical biochemical composition of particulate organic matter in the Seychelles-Chagos Thermocline Ridge (SCTR), southwestern Indian Ocean

VARIABILITY IN THE MUTAGENICITY OF ORGANIC POLLUTANTS ADSORBED ON THE PARTICULATE MATTER IN THE URBAN ENVIRONMENT

The aim of the study was to determine differences in mutagenicity of organic pollutants adsorbedon suspended particulate matter in the city centre and its outskirts. Particulate matter was collectedusing a high-performance sampler in different parts of Wrocław in summer and winter. Organiccompounds adsorbed on the particulate matter were extracted for 8 hours in Soxhlet apparatuses.The concentration of PAHs was determined using GC-MS. Mutagenicity of samples was testedusing the Ames test. The concentrations of particulate matter suspended in the atmosphere rangedfrom 23 to 144 μg/m3, and PAHs from the EPA list adsorbed on it ranged from 8.3 to 1211.6 ng/m3.Particulate matter suspended in the atmosphere collected in different places in Wrocław insummer and winter showed mutagenic activity. This effect was greater in winter than in summer.In winter, it was greater in the city centre than on its outskirts. Activation with the S9 mix fractioncaused a decrease in the mutagenic activity of most of the tested particulate matter samples againstthe TA 98 strain. This indicates the presence of mainly direct mutagens in them. The volumesof polluted air causing a mutagenic effect on the TA 98 strain without activation by the S9 mixfraction ranged from 0.25 to 35 m3. The high sensitivity of the YG 1021 and YG 1024 strains tothe mutagenic effect of pollutants adsorbed on the tested particulate matter indicates a significantshare of nitroarenes in their mutagenic activity. The differentiation of this share depended mainlyon local and momentary conditions. The exposure of residents to the genotoxic effect of pollutantsadsorbed on particulate matter increases in winter, especially in the city centre. Supplementing thecurrently used physicochemical monitoring of air pollution with a study of the mutagenic activityof pollutants adsorbed on particulate matter would allow for the assessment of this activity and theshare of certain groups of pollutants, such as nitroarenes.

THE EFFECT OF DIVERSIFIED CROP ROTATIONS ON SOIL ORGANIC CARBON DYNAMICS IN A CLAYEY TROPICAL SOIL

This study assessed the impact of crop diversification within no-till crop rotations on soil organic carbon and total nitrogen stocks, as well as on labile (Carbon and Nitrogen in the particulate organic matter) and persistent (Carbon and Nitrogen in the mineral-associated organic matter) Organic matter fractions. The objective was to identify practical indicators for monitoring public policies promoting low carbon emission agriculture. Field experiment was conducted in 2014/2015 cropping season using a complete random block design. Seven treatments were evaluated: soybean/cotton (CONTROL); maize/soybean (M/Sb); soybean/maize+brachiaria (Sb/M+Br); soybean/millet+brachiaria/crotalaria spectabiliscotton (Sb/Mt+Br/CrsCt); soybean/cotton/common beans/millet+ brachiaria (Sb/Ct/Cb/Mt+Br); millet-cotton/ soybean/maize/crotalaria spectabilis (Mt-Ct/Sb/M/Crs); crotalaria-cotton/soybean/ sorghum+brachiaria/crotalaria ochroleuca+ brachiaria (Cr-Ct/Sb/Sg+Br/Cro+Br). Sampling was done in May 2020 on an Oxisol in a neotropical savanna of the Central West region of Brazil (Capivara Experimental Research Farm of Embrapa Rice and Beans, Santo Antônio de Goiás, Goiás State, Brazil). Treatment comparisons were made after correction for equivalent soil mass per soil layer. The C-POM, N-POM, C-MAOM, and N-MAOM fractions were obtained through granulometric physical fractionation. Total SOC and SOC stocks were inadequate indicators of the impact of crop rotations on SOC. However, the distribution of C and N among the soil organic matter (SOM) fractions (C-POM, N-POM, C-MAOM, and N-MAOM) was influenced by crop rotations. Rotations with greater crop diversity, including gramineae, had higher concentration of C and N in the particulate SOC (C-POM and N-POM). Differences in rotation composition also affected the C to N ratio, particularly in the POM fraction, which was higher in rotations involving brachiaria grass and maize. Most diversified rotations contributed to maintaining higher C-POM stocks.

The Operational Performance of an Ultrafiltration Pilot Unit for the Treatment of Ultra-Concentrated Brines.

The valorization of ultra-concentrated seawater brines, named bitterns, requires preliminary purification processes, such as membrane filtration, before they can be fully exploited. This study investigates the performance of an ultrafiltration pilot plant aimed at separating organic matter and large particles from real bitterns. An empirical model for the bittern viscosity was developed to better characterize the membrane. Distinct variations in permeability, fouling resistance and rejection coefficient were observed under operational pressures ranging from 2 to 4 bar. Working at low pressure (2 bar), the pilot plant achieves permeability and rejection coefficient values of 17 L/m2hbar and 95%, respectively. Foulant behavior was characterized by determining a "fouling resistance", obtaining an average value of 1013 m-1. Tests with three distinct bittern samples were conducted to assess the influence of chemical composition and organic matter content on membrane permeability and fouling characteristics. The collected data enabled a comprehensive characterization of the ultrafiltration pilot unit working with this particular saline feed solution, which has very high technical-economic potential.

Wetland Ecosystem Service Preservation? Geochemical Changes in Systems with Mangroves and Shrimp Farms in the Northern Ecuadorean Coast

Mangrove sediments serve as paleoenvironmental records of organic matter and nutrient accumulation. Ecuador, the world’s largest producer of whiteleg shrimp Penaeus vannamei in brackish waters, lost 43% of its continental mangroves between 1969 and 1999. Currently, more than 70,000 hectares of shrimp farms operate in estuaries with mangroves and within mangrove reserves. Variations in mangrove coverage and the extent of shrimp farms are described for the period 1996–2020 for two mangrove reserves, REMACAM and RVSMERM, with an observed increase in the extent of shrimp farms in both reserves. Four sediment cores obtained from mangrove drains and drains transformed into shrimp farm infrastructures were analyzed to observe the impact of this activity on the cumulative changes in total organic carbon (TOC) content and total nitrogen (TN) content, the fractionation of stable isotopes δ13C and δ15N, as well as the TOC/TN ratio. The mangrove drains in REMACAM had 3.8 times more TOC and 2.3 times more TN than drains transformed into shrimp farms in RVSMERM, with lower TOC/TN ratios. The organic matter in sediments from sectors with a higher proportion of shrimp farms mainly came from particulate organic matter of freshwater and freshwater algae compared to mangrove drains. Increases in TOC and TN content were recorded in all analyzed sectors, which could be attributed to the cumulative impact of population growth, the development of other agricultural crops, and continental deforestation, despite the fact that proportionally, the highest increases occurred in the sector with a greater influence of shrimp farms.

Metabolites reflect variability introduced by mesoscale eddies in the North Pacific Subtropical Gyre

Mesoscale eddies significantly alter open ocean environments such as those found in the subtropical gyres that cover a large fraction of the global ocean. Previous studies have explored eddy effects on biogeochemistry and microbial community composition but not on the molecular composition of particulate organic matter. This study reports the absolute concentration of 67 metabolites and relative abundances for 640 molecular features, measured using liquid chromatography-mass spectrometry (LC-MS) following both targeted and untargeted approaches. This approach allowed us to better understand how mesoscale eddies impact the metabolome of the North Pacific Subtropical Gyre during two cruises in 2017 and 2018. We find that many metabolites track biomass trends, but metabolites like isethionic acid, homarine, and trigonelline linked to eukaryotic phytoplankton were enriched at the deep chlorophyll maximum of the cyclonic features, while degradation products such as arsenobetaine were enriched in anticyclones. In every analysis, the metabolites with the strongest responses were identified using LC-MS through untargeted metabolomics approaches, highlighting that the molecules most sensitive to environmental perturbation were not among the previously characterized metabolome. By analyzing depth variability (accounting for 20-40% of metabolomic variability across ~150 meters) and the vertical displacement of isopycnal surfaces (explaining 10-20% of variability across a sea level anomaly range of 40 centimeters and a spatial distance of 300 kilometers), this analysis constrains the importance of mesoscale eddies in shaping the chemical composition of particulate matter in the largest biomes on the planet.

Short‐term effects of a heavy dairy manure application on soil chemical and biological indicators in an irrigated semiarid cropping system

AbstractIntensive dairy production in southern Idaho is associated with the annual application of manure to croplands. However, a one‐time heavy application of manure could alternatively be used as a means to improve soil fertility and health for years or even decades, circumventing the need for frequent applications. To determine if this practice would negatively affect soil properties in the short term, we analyzed chemical and biological indicators of soil health for 2 years after dairy manure incorporation. Soil indicators measured were pH, electrical conductivity, extractable nitrogen (N) and phosphorus, total carbon (C) and N, enzyme activities, net N mineralization, soil organic C, soil protein, active C, ammonia oxidation potential, and particulate organic matter. Manure (with and without synthetic fertilizer) was found to significantly affect chemical and biological indicators in both topsoil (0–15 cm) and subsoil (15–30 cm), but the responses were greater in the subsoil. This can be attributed to the fact that manure was incorporated to approximately 30 cm via moldboard plow. All indicators responded positively to manure, except pH, which decreased slightly in the subsoil in the first year after application. Principal component analysis of chemical and biological indicators, across all years and depths, showed that the first two components explained 62% and 8.5% of the variance. While soil indicators were not adversely affected by manure, silage corn (Zea mays L.) yields in year 1 were significantly lower in manured plots, though in year 2, barley grain (Hordeum vulgare L.) yields were statistically similar among manure and fertilizer.