Dissolved organic matter (DOM) is a large and complex mixture of compounds with source inputs that differ with location, season, and environmental conditions. Here, we investigated drivers of DOM ...composition changes in a marsh‐dominated estuary off the southeastern United States. Monthly water samples were collected at a riverine and estuarine site from September 2015 to September 2016, and bulk, optical, and molecular analyses were conducted on samples before and after dark incubations. Results showed that river discharge was the primary driver changing the DOM composition at the mouth of the Altamaha River. For discharge higher than ~150 m3/s, dissolved organic carbon (DOC) concentrations and the terrigenous character of the DOM increased approximately linearly with river flow. For low discharge conditions, a clear signature of salt marsh‐derived compounds was observed in the river. At the head of Sapelo Sound, changes in DOM composition were primarily driven by river discharge and possibly by summer algae blooms. Microbial consumption of DOC was larger during periods of high discharge at both sites, potentially due to the higher mobilization and influx of fresh material to the system. The Georgia coast was hit by Hurricane Matthew in October 2016, which resulted in a large input of carbon to the estuary. The DOC concentration was ~2 times higher and DOM composition was more aromatic with a stronger terrigenous signature compared to the seasonal maximum observed earlier in the year during peak river discharge conditions. This suggests that extreme events notably impact DOM quantity and quality in estuarine regions.
Plain Language Summary
Dissolved organic matter (DOM) is a crucial component of aquatic ecosystems and characterizing how its composition and concentration change is important to better understand the carbon cycle. Composition and quantity of DOM can vary spatially and temporally due to a variety of factors, including biological activity, precipitation patterns, and proximity to source inputs such as rivers, salt marshes, and the open ocean. To track these changes, monthly water samples were collected and analyzed over the course of a year in a marsh‐dominated estuary off the Georgia coast, USA. River flow was shown to be an important factor controlling the amount and type of DOM present at both riverine (Altamaha River) and estuarine (Sapelo Sound) locations. In months with high river flow, organic matter contents were higher and had more terrestrially derived compounds compared to months with low river flow. Additionally, Hurricane Matthew was shown to significantly alter the organic matter at Sapelo Sound, suggesting that extreme events greatly impact DOM quantity and quality in estuarine regions.
Key Points
Changes in DOM composition over a year at the Altamaha River and Sapelo Sound are strongly correlated with river discharge
High river discharge conditions are characterized by DOM with stronger terrigenous signature and higher microbial utilization rates
Passage of Hurricane Matthew resulted in large input of terrigenous DOM to Sapelo Sound, greatly increasing DOC concentrations
Efforts have been dedicated to the understanding of social-ecological systems, an important focus in ethnobiological studies. In particular, ethnobiological investigations have found evidence and ...tested hypotheses over the last 30 years on the interactions between human groups and their environments, generating the need to formulate a theory for such systems. In this article, we propose the social-ecological theory of maximization to explain the construction and functioning of these systems over time, encompassing hypotheses and evidence from previous ethnobiological studies. In proposing the theory, we present definitions and two conceptual models, an environmental maximization model and a redundancy generation model. The first model seeks to address biota selection and its use by human populations. The second emphasizes how the system organizes itself from the elements that were incorporated into it. Furthermore, we provide the theoretical scenario of plant selection and use from an evolutionary perspective, which explicitly integrates the phylogenetic relationships of plants (or other living resources) and human beings.
Fugitive dust from the erosion of arid and fallow land, after harvest and during agricultural activities, can at times be the dominant source of airborne particulate matter. In order to assess the ...source contributions to a given site, chemical mass balance (CMB) modeling is typically used together with source-specific profiles for organic and inorganic constituents. Yet, the mass balance closure can be achieved only if emission profiles for all major sources are considered. While a higher degree of mass balance closure has been achieved by adding individual organic marker compounds to elements, ions, EC, and organic carbon (OC), major source profiles for fugitive dust are not available. Consequently, neither the exposure of the population living near fugitive dust sources from farm land, nor its chemical composition is known. Surface soils from crop fields are enriched in plant detritus from both above and below ground plant parts; therefore, surface soil dust contains natural organic compounds from the crops and soil microbiota. Here, surface soils derived from fields growing cotton, safflower, tomato, almonds, and grapes have been analyzed for more than 180 organic compounds, including natural lipids, saccharides, pesticides, herbicides, and polycyclic aromatic hydrocarbon (PAH). The major result of this study is that selective biogenically derived organic compounds are suitable markers of fugitive dust from major agricultural crop fields in the San Joaquin Valley. Aliphatic homologs exhibit the typical biogenic signatures of epicuticular plant waxes and are therefore indicative of fugitive dust emissions and mechanical abrasion of wax protrusions from leaf surfaces. Saccharides, among which α- and β-glucose, sucrose, and mycose show the highest concentrations in surface soils, have been proposed to be generic markers for fugitive dust from cultivated land. Similarly, steroids are strongly indicative of fugitive dust. Yet, triterpenoids reveal the most pronounced distribution differences for all types of cultivated soils examined here and are by themselves powerful markers for fugitive dust that allow differentiation between the types of crops cultivated. PAHs are also found in some surface soils, as well as persistent pesticides, e.g., DDE, Fosfall, and others.
Several ethnobotanical studies have attempted to understand the criteria for the differential use of plant resources. However, we need more effort to understand the interaction between local uses: ...how using a species for a given purpose may affect its use for another purpose. Thus, we hypothesize that high importance species in a more specialized category of use may have their use reduced for other categories with a more generalist nature. We have conducted the study in three rural communities in northeastern Brazil, set in seasonally dry tropical forest areas. We applied the free-list technique to identify woody species used for medicinal and/or wood purposes (fuelwood, construction and technology). Respondents rated the species according to their efficiency for wood purposes and their local availability. We performed a multiple regression to assess the effects of medicinal popularity, perceived availability, and perceived efficiency for wood uses over the species popularity for wood uses. Our results showed that medicinal use has a significant protective effect against wood uses. Perceived availability and efficiency were significant explanatory variables for wood use. Maintaining the medicinal importance of certain species can be a powerful tool in protecting their populations against more harmful uses.
•Previous studies have not investigated the interactive effects between use-categories in social-ecological systems.•Being valuable as medicinal for domestic purposes decreases the collection and use of native species for woody purposes.•Other factors (perceived efficiency and availability) are more important than medicinal popularity in defining woody use.•The protective effect of specialized over generalist uses should be tested under more social-ecological contexts.
•Increasing salinity favored lipoxygenase induction in terrestrial higher plant debris.•Lipoxygenases initiated autoxidative degradation of terrestrial POM in estuaries.•Autoxidative degradation of ...terrestrial POM enhanced at low and high latitude.•In temperate zones autoxidative damage of terrestrial POM more limited.
There exists a substantial amount of research on abiotic (e.g. photochemical) degradation pertaining to organic matter (OM) in the marine realm. While recent research has shown its importance in the degradation of terrestrial particulate OM (TPOM), the mechanisms involved in the induction of autoxidation in estuaries remain unclear. In this study, we propose for the first time the involvement of lipoxygenase (LOX) activity in the induction of autoxidation in mixed waters. The observation of unusual profiles of palmitoleic acid oxidation products and the presence of jasmonic acid in suspended particulate matter (SPM) collected close to the Rhône River, as well as in samples from the Mackenzie and Amazon rivers, is attributed to strong LOX activity. We show the role played by salinity in the induction of this LOX activity and provide an explanation for the differences in estuarine autoxidation level. At high latitude, lower temperatures and irradiance favor photooxidative damage to higher plant debris and, consequently, hydroperoxide production. High hydroperoxide content strongly contributes to LOX activation in mixed waters. The high resulting LOX activity enhances alkoxyl radical production and thus autoxidation. On the contrary, at low latitude, photooxidative effects are limited, and riverine autoxidation is favored. The higher hydroperoxide content of TPOM may, as a consequence, thereby also contribute to a high level of LOX activity and autoxidation in estuaries. In temperate zones, land and riverine photooxidative and autoxidative damage is limited, unlike estuaries where we observed significant LOX-induced and autoxidative damage.
Ethnobotanical studies focused on understanding how local medical systems are functionally maintained suggest that utilitarian redundancy and knowledge transmission are factors that influence the ...resilience of the system. However, to date, there have not been any studies that analyze these factors in relation to the variables that influence the variation of knowledge. Given the above, this study aims to analyze the influence of gender in the resilience of the system, using utilitarian redundancy and knowledge transmission as factors. Information from 198 married couples (396 people) was collected from the indigenous community of Fulni-ô (NE Brazil). Knowledge between men and women was analyzed based on the total number of known plants, therapeutic targets, information units, utilitarian redundancy, models of transmission, and sharing for each gender. Fulni-ô men know a greater number of plants, therapeutic targets treated with plants, and information units than women. They also had greater utilitarian redundancy. However, regarding knowledge transmission, sharing among women was greater, transmission is related to gender, and there is no difference between the numbers of models of knowledge information. In the system of local medical knowledge, gender exerts an important role in the resilience of the system. This study shows that men have a greater contribution to the structure and function of the system; however, both genders contribute to the flow of information in the system, which makes both genders important in the feedback of information.
Caatinga (dryland) plants used as fuel by rural communities were examined to verify the criteria that determined the preference and use of each species, as well as the techniques and patterns ...involved in their harvesting. Fieldwork was carried out utilizing various methodologies for collecting and analyzing data, including semi-structured interviews, guided-tours, and direct observation. Differences in knowledge concerning the use of fuelwood species were examined in terms of informant sex and age, and local availability of these resources. A total of 67 plants were cited as energy sources, of which only 27 were actually used as domestic fuel, and 10 for charcoal production. The species most well known were the most collected, independent of their availability, in spite of the fact that other highly preferred species were more available. As only a small group of plants were heavily used, it will be important to quantify the harvesting of these resources in the region in order to estimate the impact of this use on the local vegetation.
Studies have shown that inhibition of Plasmodium falciparum Purine Nucleoside Phosphorylase (PfPNP) blocks the purine salvage pathway in vitro and in vivo. In this study, PfPNP was evaluated as a ...model in the search for new inhibitors using surface plasmon resonance (SPR). Its expression, purification, oligomeric state, kinetic constants, calorimetric parameters and kinetic mechanisms were obtained. PfPNP was immobilized on a CM5 sensor chip and sensorgrams were produced through binding the enzyme to the substrate MESG and interactions between molecules contained in 10 fractions of natural extracts. The oligomeric state showed that recombinant PfPNP is a hexamer. The true steady-state kinetic parameters for the substrate inosine were: KM 17 μM, kcat 1.2 s−1, VMax 2.2 U/mg and kcat/KM 7 × 10−4; for MESG they were: KM 131 μM, kcat 2.4 s−1, VMax 4.4 U/mg and kcat/KM 1.8 × 10−4. The thermodynamic parameters for the substrate Phosphate were: ΔG − 5.8 cal mol−1, ΔH − 6.5 cal mol−1 and ΔS − 2.25 cal mol−1/degree. The ITC results demonstrated that the binding of phosphate to free PfPNP led to a significant change in heat and association constants and thermodynamic parameters. A sequential ordered mechanism was proposed as the kinetic mechanism. Three plant extracts contained molecules capable of interacting with PfPNP, showing different levels of affinity. The identification of plant extract fractions containing molecules that interact with recombinant PfPNP using SRP validates this target as a model in the search for new inhibitors. In this study, we showed for the first time the true steady-state kinetic parameters for reactions catalyzed by PfPNP and a model using PfPNP as a target for High-throughput Screening for new inhibitors through SPR. This knowledge will allow for the development of more efficient research methods in the search for new drugs against malaria.
The presence of saccharides is being reported for aerosols taken in urban, rural, and marine locales. The commonly found primary saccharides are α- and β-glucose, α- and β-fructose, sucrose, and ...mycose with lesser amounts of other monosaccharides. Saccharide polyols are also found in some airsheds and consist mainly of sorbitol, xylitol, mannitol, erythritol, and glycerol. In temperate climate areas these compounds increase from negligible concentrations in winter aerosols (usually dominated by levoglucosan and related anhydrosaccharides from biomass burning) to a maximum in late spring-summer, followed by a decrease to winter. The composition of the saccharide mixtures suggests soil and associated micro- biota as the source. Saccharide analyses of soils confirmed these compositions. Therefore, we propose resuspension of soil (also unpaved road dust) from agricultural activities as a major component of aerosol particles and the saccharides are the source specific tracers. In addition, the saccharides as well as the anhydrosaccharide derivatives from biomass burning are completely water soluble and thus contribute significantly to the total water-soluble mass of aerosols.
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