RESUMO

Although benthic microbial community offers crucial insights into ecosystem services, they are underestimated for coastal sediment monitoring. Sepetiba Bay (SB) in Rio de Janeiro, Brazil, holds long-term metal pollution. Currently, SB pollution is majorly driven by domestic effluents discharge. Here, functional prediction analysis inferred from 16S rRNA gene metabarcoding data reveals the energy metabolism profiles of benthic microbial assemblages along the metal pollution gradient. Methanogenesis, denitrification, and N2 fixation emerge as dominant pathways in the eutrophic/polluted internal sector (Spearman; p < 0.05). These metabolisms act in the natural attenuation of sedimentary pollutants. The methane (CH4) emission (mcr genes) potential was found more abundant in the internal sector, while the external sector exhibited higher CH4 consumption (pmo + mmo genes) potential. Methanofastidiosales and Exiguobacterium, possibly involved in CH4 emission and associated with CH4 consumers respectively, are the main taxa detected in SB. Furthermore, SB exhibits higher nitrous oxide (N2O) emission potential since the norB/C gene proportions surpass nosZ up to 4 times. Blastopirellula was identified as the main responsible for N2O emissions. This study reveals fundamental contributions of the prokaryotic community to functions involved in greenhouse gas emissions, unveiling their possible use as sentinels for ecosystem monitoring.

Assuntos

RESUMO

Introduction: The litterfall production, foliar nutrient dynamics and decomposition are essential to maintain nutrient cycling, soil fertility, and carbon regulation in terrestrial ecosystems. With several studies addressing the variation of these processes, their dynamics in tropical dry forests (TDFs) remain unclear, due to its complex interaction of biotic and abiotic factors. Objective: To evaluate litterfall, nutrient potential return and use efficiency, and decomposition variation in a TDF successional gradient in Tolima, Colombia. Methods: We quantified litterfall from November 2017 to October 2019 in 12 plots distributed in four successional stages: initial, early, intermediate, and late forests. We identified key tree species in foliar litter production and characterized the foliar decomposition of these species. At the community level, we quantified the C, N and P potential return, the N and P use efficiency, and the C:N and N:P ratio. Subsequently, we analyze relationships between vegetation characteristics and some soil chemical properties with these ecological processes. Results: We found that total litterfall in late forests (8.46 Mg ha-1 y-1) was double that found in initial forests (4.45 Mg ha-1 y-1). Decomposition was higher in initial (k = 1.28) compared to intermediate (k = 0.97) and late forests (k = 0.87). The nutrient potential return didn't change along succession, but it did show differences between study sites. The structural development and species richness favored litterfall, while soil chemical conditions influenced nutrient returns and decomposition. Conclusions: TDFs could recover key ecosystem function related to litterfall and nutrient dynamics after disturbances cessation; however, the soil quality is fundamental in return and release of nutrients.

Introducción: La producción de hojarasca, la dinámica de nutrientes foliares y la descomposición son esenciales para mantener el ciclo de nutrientes, la fertilidad del suelo y la regulación del carbono en ecosistemas terrestres. Con diversos estudios que abordan estos procesos, su variación en los bosques secos tropicales (BSTs) permanece incierta, por su compleja interacción de factores bióticos y abióticos. Objetivo: Evaluar la caída de hojarasca, el retorno potencial de nutrientes y eficiencia de uso, y la variación en descomposición en un gradiente sucesional de un BST en Tolima, Colombia. Métodos: Cuantificamos la caída de hojarasca entre noviembre 2017 y octubre 2019 en 12 parcelas distribuidas en cuatro estados sucesionales: bosque inicial, temprano, intermedio y tardío. Identificamos las especies arbóreas clave en la producción de hojarasca y caracterizamos la descomposición foliar de estas especies. A nivel comunitario, cuantificamos el retorno potencial de C, N y P, la eficiencia de uso de N y P y la relación C:N y N:P. Posteriormente, analizamos las relaciones entre las características de la vegetación y algunas propiedades químicas del suelo con estos procesos ecológicos. Resultados: Encontramos que la caída total de hojarasca en los bosques tardíos (8.46 Mg ha-1 año-1) fue el doble de la hallada en bosques iniciales (4.45 Mg ha-1 año-1). La descomposición fue mayor en bosques iniciales (k = 1.28) en comparación con bosques intermedios (k = 0.97) y tardíos (k = 0.87). El retorno potencial de nutrientes no cambió con el avance de la sucesión vegetal, pero exhibió diferencias entre los sitios de estudio. El desarrollo estructural y la riqueza de especies favorecieron la caída de hojarasca, mientras que las condiciones químicas del suelo influyeron en el retorno de nutrientes y descomposición. Conclusiones: Los BSTs tienen la capacidad de recuperar la función ecosistémica de aporte de hojarasca fina, retorno y liberación de nutrientes después del cese de alteraciones antrópicas; sin embargo, la calidad del suelo es fundamental en el retorno y liberación de nutrientes.

Assuntos

RESUMO

Mangroves under macro-tidal regimes are global carbon sequestration hotspots but the microbial drivers of biogeochemical cycles remain poorly understood. Here, we investigate the drivers of mangrove microbial community composition across a porewater-creek-estuary-ocean continuum. Observations were performed on the Amazon region in one of the largest mangrove systems worldwide with effective sequestration of organic carbon buried in soils and dissolved carbon via outwelling to the ocean. The potential export to the adjacent oceanic region ranged from 57 to 380 kg of dissolved and particulate organic carbon per second (up to 33 thousand tons C per day). Macro tides modulated microbial communities and their metabolic processes, e.g., anoxygenic phototrophy, sulfur, and nitrogen cycling. Respiration, sulfur metabolism and dissolved organic carbon (DOC) levels were linked to functional groups and microbial cell counts. Total microbial counts decreased and cyanobacteria counts peaked in the spring tide. The microbial groups driving carbon, nitrogen, sulfur and methane cycles were consistent across all spatial scales. Taxonomic groups engaged in sulfur cycling (Allochromatium, Desulfovibrio, and Thibacillus) within mangroves were abundant at all scales. Tidally-driven porewater exchange within mangroves drove a progressive increase of sulfur cycle taxonomic groups and their functional genes both temporally (tidal cycles) and spatially (from mangrove porewater to continental shelf). Overall, we revealed a unified and consistent response of microbiomes at different spatial and temporal scales to tidally-driven mangrove porewater exchange.

Assuntos

RESUMO

Microplastics (MPs) correspond to plastics between 0.1 µm and 5 mm in diameter, and these can be intentionally manufactured to be microscopic or generated from the fragmentation of larger plastics. Currently, MP contamination is a complicated subject due to its accumulation in the environment. They are a novel surface and a source of nutrients in soils because MPs can serve as a substrate for the colonization of microorganisms. Its presence in soil triggers physical (stability of aggregates, soil bulk density, and water dynamics), chemical (nutrients availability, organic matter, and pH), and biological changes (microbial activity and soil fauna). All these changes alter organic matter degradation and biogeochemical cycles such as the nitrogen (N) cycle, which is a key predictor of ecological stability and management in the terrestrial ecosystem. This review aims to explore how MPs affect the N cycle in the soil, the techniques to detect it in soil, and their effects on the physicochemical and biological parameters, emphasizing the impact on the main bacterial groups, genes, and enzymes associated with the different stages of the N cycle.

Assuntos

RESUMO

Enzyme activities (EAs) respond to contamination in several ways depending on the chemical form and content of heavy metals and metalloids (HMs) and their interactions with various soil properties. A systematic and mechanistic understanding of EA responses to HM contamination in soil is necessary for predicting the consequences for nutrient availability and the cycling of carbon (C), nitrogen (N), phosphorus (P) and sulphur (S). In this study, a meta-analysis based on 671 observations found the activities of seven enzymes to decrease in response to soil contamination with Pb, Zn, Cd, Cu and As. HM contamination linearly reduced the activities of all enzymes in the following order: arylsulfatase > dehydrogenase > ß-glucosidase > urease > acid phosphatase > alkaline phosphatase > catalase. The activities of two endoenzymes: arylsulfatase (partly as exoenzyme) and dehydrogenase were reduced by 72% and 64%, respectively. These reductions were two times greater than of exoenzymes: ß-glucosidase, urease, acid phosphatase, alkaline phosphatase and catalase (partly endoenzyme). This reflects the much stronger impact of HMs on living microorganisms and their endoenzymes than on extracellular enzymes stabilized on clay minerals and organic matter. Increasing clay content weakened the negative effects of HM contamination on EAs. All negative effects of HMs on EAs decreased with soil depth because HMs remain mainly in the topsoil. EAs involved in the cycling of C and S were more affected by HMs than the enzymes associated with the cycling of N and P. Consequently, HM contamination may alter the stoichiometry of C, N, P and S released by enzymatic decomposition of organic compounds that consequently affect microbial community structure and activity.

Assuntos

RESUMO

Southwestern Brazilian Amazonia has suffered intense forest conversion in a short period of time (~60 years) and deforestation is ongoing. Around 70% of the deforested area has been designated for cattle ranching. This forest clearing and pasture establishment is abruptly disrupting the functioning of the ecosystem. In this paper, we provide an overview of the effects of land conversion from forest to pasture on the soil and aquatic systems. Forest conversion to pasture has two clear effects: a) an on-site effect on the hillslope domain and 2) an off-site effect on the river system. The conversion of forest to pasture affects the soil physical-chemical properties, soil carbon content, water resources, and aquatic system. However, many of these changes are not straightforward or obvious. For example, in some conditions, the soil carbon stock increases in pasture. Despite the advances in our understanding of the effects of land conversion on environmental processes, knowledge gaps persist, and we identify some research needs.

Assuntos

RESUMO

Mercury (Hg) is a toxic metal that is transported globally through the atmosphere. The emission of Hg from mineral reservoirs and subsequent recycling in surface reservoirs (i.e., soil/biomass, ocean, and atmosphere) are fundamental to the modern global Hg cycle, yet past emissions from anthropogenic and natural sources are not fully constrained. We use a sediment core from Yanacocha, a headwater lake in southeastern Peru, to study the anthropogenic and natural controls on atmospheric Hg deposition during the Holocene. From 12.3 to 3.5 ka, Hg fluxes in the record are relatively constant (mean ± 1σ: 1.4 ± 0.6 µg m-2 a-1, n = 189). Past Hg deposition does not correlate with changes in regional temperature and precipitation, inferred from nearby paleoclimate records, or with most large volcanic events that occurred regionally, in the Andean Central Volcanic Zone (~300-400 km from Yanacocha), and globally. In B.C. 1450 (3.4 ka), Hg fluxes abruptly increased and reached the Holocene-maximum flux (6.7 µg m-2 a-1) in B.C. 1200, concurrent with a ~100-year peak in Fe and chalcophile metals (As, Ag, Tl) and the presence of framboidal pyrite. Continuously elevated Hg fluxes from B.C. 1200-500 suggest a protracted mining-dust source near Yanacocha that is identical in timing to documented pre-Incan cinnabar mining in central Peru. During Incan and Colonial time (A.D. 1450-1650), Hg deposition remains elevated relative to background levels but lower relative to other Hg records from sediment cores in central Peru, indicating a limited spatial extent of preindustrial Hg emissions. Hg fluxes from A.D. 1980 to 2011 (4.0 ± 1.0 µg m-2 a-1, n = 5) are 3.0 ± 1.5 times greater than pre-anthropogenic fluxes and are similar to modern fluxes documented in remote lakes around the world.

RESUMO

The coupling of subseafloor microbial life to oceanographic and atmospheric conditions is poorly understood. We examined diagenetic imprints and lipid biomarkers of past subseafloor microbial activity to evaluate its response to glacial-interglacial cycles in a sedimentary section drilled on the Peruvian shelf (Ocean Drilling Program Leg 201, Site 1229). Multiple and distinct layers of diagenetic barite and dolomite, i.e., minerals that typically form at the sulfate-methane transition (SMT), occur at much shallower burial depth than the present SMT around 30 meters below seafloor. These shallow layers co-occur with peaks of (13)C-depleted archaeol, a molecular fossil of anaerobic methane-oxidizing Archaea. Present-day, non-steady state distributions of dissolved sulfate also suggest that the SMT is highly sensitive to variations in organic carbon flux to the surface shelf sediments that may lead to shoaling of the SMT. Reaction-transport modeling substantiates our hypothesis that shallow SMTs occur in response to cyclic sediment deposition with a high organic carbon flux during interglacials and a low organic carbon flux during glacial stages. Long diffusion distances expectedly dampen the response of deeply buried microbial communities to changes in sediment deposition and other oceanographic drivers over relatively short geological time scales, e.g., glacial-interglacial periods. However, our study demonstrates how dynamically sediment biogeochemistry of the Peru Margin has responded to glacial-interglacial change and how these changes are now preserved in the geological record. Such changes in subsurface biogeochemical zonation need to be taken into account to assess the role of the subseafloor biosphere in global element and redox cycling.

Assuntos

RESUMO

Although only a small amount of the Earth's water exists as continental surface water bodies, this compartment plays an important role in the biogeochemical cycles connecting the land to the atmosphere. The territory of Brazil encompasses a dense river net and enormous number of shallow lakes. Human actions have been heavily influenced by the inland waters across the country. Both biodiversity and processes in the water are strongly driven by seasonal fluvial forces and/or precipitation. These macro drivers are sensitive to climate changes. In addition to their crucial importance to humans, inland waters are extremely rich ecosystems, harboring high biodiversity, promoting landscape equilibrium (connecting ecosystems, maintaining animal and plant flows in the landscape, and transferring mass, nutrients and inocula), and controlling regional climates through hydrological-cycle feedback. In this contribution, we describe the aquatic ecological responses to climate change in a conceptual perspective, and we then analyze the possible climate-change scenarios in different regions in Brazil. We also indentify some potential biogeochemical signals in running waters, natural lakes and man-made impoundments. The possible future changes in climate and aquatic ecosystems in Brazil are highly uncertain. Inland waters are pressured by local environmental changes because of land uses, landscape fragmentation, damming and diversion of water bodies, urbanization, wastewater load, and level of pollutants can alter biogeochemical patterns in inland waters over a shorter term than can climate changes. In fact, many intense environmental changes may enhance the effects of changes in climate. Therefore, the maintenance of key elements within the landscape and avoiding extreme perturbation in the systems are urgent to maintain the sustainability of Brazilian inland waters, in order to prevent more catastrophic future events.

Embora apenas uma pequena quantidade de água da Terra esteja reservada em corpos d'água da superfície continental, esses ambientes desempenham papel importante nos ciclos biogeoquímicos, conectando a superfície à atmosfera. O território brasileiro é recortado por uma densa rede fluvial e exibe um enorme número de lagos rasos. Impactos de natureza humana têm sido intensos modificadores de ecossistemas límnicos. A biodiversidade e os processos ecossistêmicos são fortemente modulados por forças sazonais fluvial e/ou precipitação. Essas macroforçantes ecológicas respondem às mudanças climáticas. As águas interiores são ecossistemas com elevada biodiversidade, promovem transferências de energia dentro da paisagem, conectando os ecossistemas, e atuam na manutenção de fluxos de matérias - animais, vegetais, nutrientes e inóculos. Esses ecossistemas controlam o clima numa escala regional. Neste capítulo, são descritas algumas respostas dos ecossistemas aquáticos às alterações climáticas, tanto conceitualmente como analisando os possíveis cenários de mudanças climáticas em diferentes regiões no Brasil. Potenciais sinais biogeoquímicos em diferentes ecossistemas límnicos brasileiros foram identificados. Os ecossistemas límnicos são pressionados pelas atividades do uso do solo, pela fragmentação da paisagem, pelo represamento e pelo desvio de rios, pela urbanização, pela carga de águas residuais e do nível de poluentes. Essas ações perturbadoras podem alterar os padrões biogeoquímicos nas águas interiores numa escala temporal mais curta quando comparada às mudanças climáticas. A manutenção da sustentabilidade das ecossistemas aquáticos brasileiros é urgente de modo a prevenir futuros eventos catastróficos.

RESUMO

Although only a small amount of the Earth's water exists as continental surface water bodies, this compartment plays an important role in the biogeochemical cycles connecting the land to the atmosphere. The territory of Brazil encompasses a dense river net and enormous number of shallow lakes. Human actions have been heavily influenced by the inland waters across the country. Both biodiversity and processes in the water are strongly driven by seasonal fluvial forces and/or precipitation. These macro drivers are sensitive to climate changes. In addition to their crucial importance to humans, inland waters are extremely rich ecosystems, harboring high biodiversity, promoting landscape equilibrium (connecting ecosystems, maintaining animal and plant flows in the landscape, and transferring mass, nutrients and inocula), and controlling regional climates through hydrological-cycle feedback. In this contribution, we describe the aquatic ecological responses to climate change in a conceptual perspective, and we then analyze the possible climate-change scenarios in different regions in Brazil. We also indentify some potential biogeochemical signals in running waters, natural lakes and man-made impoundments. The possible future changes in climate and aquatic ecosystems in Brazil are highly uncertain. Inland waters are pressured by local environmental changes because of land uses, landscape fragmentation, damming and diversion of water bodies, urbanization, wastewater load, and level of pollutants can alter biogeochemical patterns in inland waters over a shorter term than can climate changes. In fact, many intense environmental changes may enhance the effects of changes in climate. Therefore, the maintenance of key elements within the landscape and avoiding extreme perturbation in the systems are urgent to maintain the sustainability of Brazilian inland waters, in order to prevent more catastrophic future events.

Embora apenas uma pequena quantidade de água da Terra esteja reservada em corpos d'água da superfície continental, esses ambientes desempenham papel importante nos ciclos biogeoquímicos, conectando a superfície à atmosfera. O território brasileiro é recortado por uma densa rede fluvial e exibe um enorme número de lagos rasos. Impactos de natureza humana têm sido intensos modificadores de ecossistemas límnicos. A biodiversidade e os processos ecossistêmicos são fortemente modulados por forças sazonais fluvial e/ou precipitação. Essas macroforçantes ecológicas respondem às mudanças climáticas. As águas interiores são ecossistemas com elevada biodiversidade, promovem transferências de energia dentro da paisagem, conectando os ecossistemas, e atuam na manutenção de fluxos de matérias - animais, vegetais, nutrientes e inóculos. Esses ecossistemas controlam o clima numa escala regional. Neste capítulo, são descritas algumas respostas dos ecossistemas aquáticos às alterações climáticas, tanto conceitualmente como analisando os possíveis cenários de mudanças climáticas em diferentes regiões no Brasil. Potenciais sinais biogeoquímicos em diferentes ecossistemas límnicos brasileiros foram identificados. Os ecossistemas límnicos são pressionados pelas atividades do uso do solo, pela fragmentação da paisagem, pelo represamento e pelo desvio de rios, pela urbanização, pela carga de águas residuais e do nível de poluentes. Essas ações perturbadoras podem alterar os padrões biogeoquímicos nas águas interiores numa escala temporal mais curta quando comparada às mudanças climáticas. A manutenção da sustentabilidade das ecossistemas aquáticos brasileiros é urgente de modo a prevenir futuros eventos catastróficos.

Assuntos

RESUMO

Although only a small amount of the Earth's water exists as continental surface water bodies, this compartment plays an important role in the biogeochemical cycles connecting the land to the atmosphere. The territory of Brazil encompasses a dense river net and enormous number of shallow lakes. Human actions have been heavily influenced by the inland waters across the country. Both biodiversity and processes in the water are strongly driven by seasonal fluvial forces and/or precipitation. These macro drivers are sensitive to climate changes. In addition to their crucial importance to humans, inland waters are extremely rich ecosystems, harboring high biodiversity, promoting landscape equilibrium (connecting ecosystems, maintaining animal and plant flows in the landscape, and transferring mass, nutrients and inocula), and controlling regional climates through hydrological-cycle feedback. In this contribution, we describe the aquatic ecological responses to climate change in a conceptual perspective, and we then analyze the possible climate-change scenarios in different regions in Brazil. We also indentify some potential biogeochemical signals in running waters, natural lakes and man-made impoundments. The possible future changes in climate and aquatic ecosystems in Brazil are highly uncertain. Inland waters are pressured by local environmental changes because of land uses, landscape fragmentation, damming and diversion of water bodies, urbanization, wastewater load, and level of pollutants can alter biogeochemical patterns in inland waters over a shorter term than can climate changes. In fact, many intense environmental changes may enhance the effects of changes in climate. Therefore, the maintenance of key elements within the landscape and avoiding extreme perturbation in the systems are urgent to maintain the sustainability of Brazilian inland waters, in order to prevent more catastrophic future events.

Embora apenas uma pequena quantidade de água da Terra esteja reservada em corpos d'água da superfície continental, esses ambientes desempenham papel importante nos ciclos biogeoquímicos, conectando a superfície à atmosfera. O território brasileiro é recortado por uma densa rede fluvial e exibe um enorme número de lagos rasos. Impactos de natureza humana têm sido intensos modificadores de ecossistemas límnicos. A biodiversidade e os processos ecossistêmicos são fortemente modulados por forças sazonais fluvial e/ou precipitação. Essas macroforçantes ecológicas respondem às mudanças climáticas. As águas interiores são ecossistemas com elevada biodiversidade, promovem transferências de energia dentro da paisagem, conectando os ecossistemas, e atuam na manutenção de fluxos de matérias - animais, vegetais, nutrientes e inóculos. Esses ecossistemas controlam o clima numa escala regional. Neste capítulo, são descritas algumas respostas dos ecossistemas aquáticos às alterações climáticas, tanto conceitualmente como analisando os possíveis cenários de mudanças climáticas em diferentes regiões no Brasil. Potenciais sinais biogeoquímicos em diferentes ecossistemas límnicos brasileiros foram identificados. Os ecossistemas límnicos são pressionados pelas atividades do uso do solo, pela fragmentação da paisagem, pelo represamento e pelo desvio de rios, pela urbanização, pela carga de águas residuais e do nível de poluentes. Essas ações perturbadoras podem alterar os padrões biogeoquímicos nas águas interiores numa escala temporal mais curta quando comparada às mudanças climáticas. A manutenção da sustentabilidade das ecossistemas aquáticos brasileiros é urgente de modo a prevenir futuros eventos catastróficos.

RESUMO

Florestas ripárias, mosaicos de vegetação e áreas alagadas têm papel fundamental na proteção dos recursos hídricos mantendo a qualidade da água em excelentes condições para abastecimento e recarregado aquíferos repondo, portanto, volumes substanciais de águas para o componente subterrâneo. A remoção de florestas ripárias e áreas alagadas têm um efeito extremamente negativo degradando a qualidade das águas superficiais e subterrâneas, acelerando a sedimentação de lagoas, represas e rios, e diminuindo o estoque de água nas nascentes e aquíferos. Todos os serviços ambientais dos ecossistemas aquáticos ficam comprometidos com o desmatamento e remoção de áreas naturalmente alagadas, portanto a preservação destas áreas é essencial para regular tanto o ciclo hidrológicos como os ciclos biogeoquímicos. A remoção destas áreas torna insustentável a agricultura em curto prazo.

Mosaics of vegetation, riparian forests, and wetlands have an important quantitative and qualitative role on the hydrological cycle. Riparian forests protect the water quality of rivers, lakes and reservoirs. Wetlands control floods, sedimentation and regulate the water quality by enhancing processes such as denitrification, phosphorus and heavy metal retention. Both ecosystems of transition are fundamental. The removal of wetlands and forests (riparian and mosaics of vegetation) affects environmental services of these ecosystems, causing loss of economic assets of the capital natural and accelerating degradation of rivers, lakes, reservoirs and the watersheds. Protection of these ecosystems of transition is thus fundamental for the development of agriculture. The loss of services affects society, human health, increasing costs of recovery and deteriorating human-ecological relationships.