High methane concentrations in tidal salt marsh soils: Where does the methane go?

Tidal salt marshes produce and emit CH4 . Therefore, it is critical to understand the biogeochemical controls that regulate CH4 spatial and temporal dynamics in wetlands. The prevailing paradigm assumes that acetoclastic methanogenesis is the dominant pathway for CH4 production, and higher salinity concentrations inhibit CH4 production in salt marshes. Recent evidence shows that CH4 is produced within salt marshes via methylotrophic methanogenesis, a process not inhibited by sulfate reduction. To further explore this conundrum, we performed measurements of soil-atmosphere CH4 and CO2 fluxes coupled with depth profiles of soil CH4 and CO2 pore water gas concentrations, stable and radioisotopes, pore water chemistry, and microbial community composition to assess CH4 production and fate within a temperate tidal salt marsh. We found unexpectedly high CH4 concentrations up to 145,000 µmol mol-1 positively correlated with S2- (salinity range: 6.6-14.5 ppt). Despite large CH4 production within the soil, soil-atmosphere CH4 fluxes were low but with higher emissions and extreme variability during plant senescence (84.3 ± 684.4 nmol m-2 s-1 ). CH4 and CO2 within the soil pore water were produced from young carbon, with most Δ14 C-CH4 and Δ14 C-CO2 values at or above modern. We found evidence that CH4 within soils was produced by methylotrophic and hydrogenotrophic methanogenesis. Several pathways exist after CH4 is produced, including diffusion into the atmosphere, CH4 oxidation, and lateral export to adjacent tidal creeks; the latter being the most likely dominant flux. Our findings demonstrate that CH4 production and fluxes are biogeochemically heterogeneous, with multiple processes and pathways that can co-occur and vary in importance over the year. This study highlights the potential for high CH4 production, the need to understand the underlying biogeochemical controls, and the challenges of evaluating CH4 budgets and blue carbon in salt marshes.

Las marismas salinas producen y emiten CH4 . Por lo tanto, es esencial comprender los controles biogeoquímicos que regulan la dinámica espacial y temporal del CH4 en estos humedales. El paradigma predominante asume que la metanogénesis acetoclástica es la vía dominante para la producción de CH4 y que altas concentraciones de salinidad inhiben la producción de CH4 en estos ecosistemas. Hay evidencia que el CH4 se produce las marismas salinas a través de la metanogénesis metilotrófica, un proceso no inhibido por la reducción del sulfato. Para explorar esta paradoja, realizamos mediciones de los flujos de CH4 y CO2 del suelo a la atmósfera junto con perfiles de concentraciones de CH4 y CO2 en el suelo, isótopos estables y radioisótopos, química del agua y composición de la comunidad microbiana para evaluar la producción y el destino del CH4 en una marisma salina templada. Encontramos concentraciones de CH4 sorprendentemente altas de hasta 145,000 µmol mol−1 correlacionadas positivamente con S2− (rango de salinidad: 6.6 a 14.5 ppt). A pesar de la gran producción de CH4 en el suelo, los flujos de CH4 del suelo a la atmósfera fueron bajos, pero con mayores emisiones y variabilidad extrema durante la época de senescencia de las plantas (84.3 ± 684.4 nmol m−2 s−1 ). El CH4 y el CO2 en el suelo se produjeron a partir de carbono joven, con la mayoría de los valores Δ14 C-CH4 y Δ14 C-CO2 en o por encima de valores modernos. Encontramos evidencia de que el CH4 en los suelos fue producido por metanogénesis metilotrófica e hidrogenotrófica. Existen varias vías que el CH4 producido sigue, incluida la difusión hacia la atmósfera, la oxidación del CH4 y la exportación lateral a arroyos adyacentes a la marisma; siendo este último el flujo dominante más probable. Nuestros hallazgos demuestran que la producción y los flujos de CH4 son biogeoquímicamente heterogéneos, con múltiples procesos y vías que pueden coexistir y variar en importancia a lo largo del año. Este estudio destaca el potencial de alta producción de CH4 , la necesidad de comprender los controles biogeoquímicos de la producción de CH4 y los retos que existen para evaluar las reservas de CH4 y el carbono azul en marismas salinas.

Reference library for microbial source tracking in the mid-Atlantic United States.

Microbial source tracking can determine fecal contamination but requires a relevant, sizable reference library for analysis. We provide a reference library of 100+ fecal microbiome samples relevant to mid-Atlantic United States ecosystems. Included are wild and domesticated fauna, wastewater, and septic samples applicable to Delaware source tracking studies.

The potential interplay between the glandular microbiome and scent marking behavior in owl monkeys (Aotus nancymaae).

In mammals, scent marking behavior is a pervasive form of chemical communication that regulates social interactions within and between groups. Glandular microbiota consist of bacterial communities capable of producing chemical cues used in olfactory communication. Despite countless studies on scent marking in primates, few have examined the microbiota associated with glandular secretions. Nancy Ma's owl monkeys (Aotus nancymaae) are nocturnal, socially monogamous primates that frequently scent mark using their subcaudal glands. Previous analyses revealed that unique chemical signatures of Aotus may convey information about sex and age. We used positive reinforcement to sample the subcaudal glands of 23 captive owl monkeys to describe their glandular microbiomes and examine how patterns in these bacterial communities vary with age, sex, rearing environment and/or social group (pair identity). We coupled these analyses with behavioral observations to examine patterns in their scent marking behavior. We isolated 31 bacterial species from Phyla Firmicutes, Proteobacteria, and Actinobacteria, consistent with the dermal and glandular microbiomes of other primates. Several bacterial taxa we identified produce volatile organic compounds, which may contribute to olfactory communication. These bacterial communities are best predicted by an interaction between sex, rearing environment and pair identity rather than any of these variables alone. Within mated pairs of A. nancymaae, males and females scent mark their nest boxes at similar frequencies. In some pairs, rates of scent marking by males and females fluctuated over time in a similar manner. Pairs that had been together longer tended to exhibit the greatest similarities in their rates of scent marking. Together, these findings suggest that scent marking behavior and close social interactions with pair mates in Aotus may influence bacterial transmission and their glandular microbiomes. Chemical communication, including coordinated scent marking, may play a role in strengthening pair bonds, signaling pair status and/or in mate guarding in this socially monogamous primate.