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Inland aquatic ecosystems are valuable sentinels of anthropic-associated changes (e.g., agriculture and tourism). Eutrophication has become of primary importance in altering aquatic ecosystem functioning. Quantifying the CO2 emissions by inland aquatic ecosystems of different trophic statuses may provide helpful information about the role of eutrophication on greenhouse gas emissions. This study investigated diel and seasonal carbon dioxide (CO2) concentrations and emissions in three tropical karst lakes with different trophic statuses. We measured CO2 emissions using static floating chambers twice daily during the rainy/warm and dry/cold seasons while the lakes were thermally stratified and mixed, respectively. The CO2 concentration was estimated by gas chromatography and photoacoustic spectroscopy. The results showed a significant seasonal variation in the dissolved CO2 concentration (CCO2) and the CO2 flux (FCO2), with the largest values in the rainy/warm season but not along the diel cycle. The CCO2 values ranged from 13.3 to 168.6 µmol L−1 averaging 41.9 ± 35.3 µmol L−1 over the rainy/warm season and from 12.9 to 38.0 µmol L−1 with an average of 21.0 ± 7.2 µmol L−1 over the dry/cold season. The FCO2 values ranged from 0.2 to 12.1 g CO2 m−2 d −1 averaging 4.9 ± 4.0 g CO2 m−2 d −1 over the rainy/warm season and from 0.1 to 1.7 g CO2 m−2 d −1 with an average of 0.8 ± 0.5 g CO2 m−2 d −1 over the dry/cold season. During the rainy/warm season the emission was higher in the eutrophic lake San Lorenzo (9.1 ± 1.2 g CO2 m−2 d−1), and during the dry/cold the highest emission was recorded in the mesotrophic lake San José (1.42 ± 0.2 g CO2 m−2 d−1). Our results indicated that eutrophication in tropical karst lakes increased CO2 evasion rates to the atmosphere mainly due to the persistence of anoxia in most of the lake’s water column, which maintained high rates of anaerobic respiration coupled with the anaerobic oxidation of methane. Contrarily, groundwater inflows that pro

Enmarcada en la teoría de la resiliencia, medios de vida sostenibles y vulnerabilidad, esta investigación se propuso responder ¿Cómo ha cambiado la resiliencia a las inundaciones en hogares y comunidades ubicadas en las partes bajas de las cuencas de los ríos Achiguate y Sis-Icán? La investigación involucró cuatro actividades principales: i) un análisis y caracterización de los eventos de inundación influenciados por eventos hidrometeorológicos extremos basado en técnicas de Sistemas de Información Geográfica -SIG-; ii) un análisis de la dinámica del cauce de las dos principales corrientes en ambas zonas de estudio, empleando métodos de ciencias naturales como la hidrología y la geomorfología; iii) una evaluación de la resiliencia comunitaria a través de técnicas sociales (entrevistas y aplicación de cuestionarios a hogares) y socioecológicas y, iv) la elaboración de escenarios de resiliencia para ambos territorios basado en modelos conceptuales y modelación

Sulfur (S) is considered an essential nutrient for “LIVING BEINGS”, there are few studies that comprehensively analyze the dynamics of S in the soil and the role of microorganisms in the transformation of molecules with S. This review aims to analyze two key processes of S dynamics in soil: mineralization and immobilization. These processes are critical in the soil bioavailability of S and are carried out by the soil microbial community (CMS). All of the above, in order for the reader to acquire a comprehensive vision of mineralization and immobilization processes of S and notice the importance of these processes for the appropriate soil management., El azufre (S) es un nutriente esencial para los seres vivos, sin embargo, existen pocos trabajos sobre su dinámica en el suelo y sobre la importancia de la intervención de los microorganismos en la transformación de las moléculas de S. Esta revisión tiene como objetivo analizar la trascendencia de dos procesos que regulan la dinámica de este elemento: la mineralización en la que intervienen diversas enzimas y la inmovilización que atañe a la adquisición de compuestos con azufre, ambos determinantes en la biodisponibilidad de este elemento, relativa a su abundancia y a sus propiedades, que en gran medida realiza la comunidad microbiana del suelo (CMS). Lo anterior, con la finalidad de mostrar además de los pormenores de la capacidad bioquímica de estos mecanismos, el valor de su función en la naturaleza y su relevancia para la conservación del suelo, a través de un manejo adecuado del mismo.

Rivers are important sites for carbon (C) transport and critical components of the global C cycle that is currently not well constrained. However, little is known about C species’ longitudinal and temporal changes in large tropical rivers. The Usumacinta River is Mexico’s main lotic system and the tenth largest in North America. Being a tropical river, it has a strong climatic seasonality. This study aims to evaluate how organic (DOC and POC) and inorganic (DIC and PIC) carbon change spatially and seasonally along the Usumacinta River (medium and lower basin) in rainy (RS-2017) and dry (DS-2018) seasons and to estimate C fluxes into the southern Gulf of Mexico. Concentrations of DOC, POC, DIC, and PIC ranged from 0.88 to 7.11 mg L−1, 0.21 to 3.78 mg L−1, 15.59 to 48.27 mg L−1 and 0.05 to 1.51 mg L−1, respectively. DOC was the dominant organic species (DOC/POC > 1). It was ~doubled in RS and showed a longitudinal increase, probably through exchange with wetlands and floodplains. Particulate carbon showed a positive relationship with the total suspended solids, suggesting that in RS, it derived from surface erosion and runoff in the watershed. DIC is reported for the first time as the highest concentration measured in tropical rivers in America. It was higher in the dry season without a longitudinal trend. The C mass inflow–outflow balance in the RS suggested net retention (DOC and POC sink) in floodplains. In contrast, in the DS, the balance suggested that floodplains supply (C source) autochthonous DOC and POC. The lower Usumacinta River basin is a sink for DIC in both seasons. Finally, the estimated annual C export for the Usumacinta-Grijalva River was 2.88 (2.65 to 3.14) Tg yr−1, of which DIC was the largest transported fraction (85%), followed by DOC (10%), POC (4%), and PIC (<1%). This investigation is the first to present the C loads in a Mexican river.