Fire transforms effects of terrestrial subsidies on aquatic ecosystem structure and function.

Fire can lead to transitions between forest and grassland ecosystems and trigger positive feedbacks to climate warming by releasing CO into the atmosphere. Climate change is projected to increase the prevalence and severity of wildfires. However, fire effects on the fate and impact of terrestrial organic matter (i.

Selection for oligotrophy among bacteria inhabiting host microbiomes.

Understanding how natural selection has historically shaped the traits of microbial populations comprising host microbiomes would help predict how the functions of these microbes may continue to evolve over space and time. Numerous host-associated microbes have been found to adapt to their host, sometimes becoming obligate symbionts, whereas free-living microbes are best known to adapt to their surrounding environment. Our study assessed the selective pressures of both the host environment and the surrounding external environment in shaping the functional potential of host-associated bacteria.

Multiple sources of aerobic methane production in aquatic ecosystems include bacterial photosynthesis.

Aquatic ecosystems are globally significant sources of the greenhouse gas methane to the atmosphere. Until recently, methane production was thought to be a strictly anaerobic process confined primarily to anoxic sediments. However, supersaturation of methane in oxygenated waters has been consistently observed in lakes and the ocean (termed the 'methane paradox'), indicating that methane can be produced under oxic conditions through unclear mechanisms.

Substantial oxygen consumption by aerobic nitrite oxidation in oceanic oxygen minimum zones.

Oceanic oxygen minimum zones (OMZs) are globally significant sites of biogeochemical cycling where microorganisms deplete dissolved oxygen (DO) to concentrations <20 µM. Amid intense competition for DO in these metabolically challenging environments, aerobic nitrite oxidation may consume significant amounts of DO and help maintain low DO concentrations, but this remains unquantified. Using parallel measurements of oxygen consumption rates and N-nitrite oxidation rates applied to both water column profiles and oxygen manipulation experiments, we show that the contribution of nitrite oxidation to overall DO consumption systematically increases as DO declines below 2 µM.

Biogeochemistry and hydrography shape microbial community assembly and activity in the eastern tropical North Pacific Ocean oxygen minimum zone.

Oceanic oxygen minimum zones (OMZs) play a pivotal role in biogeochemical cycles due to extensive microbial activity. How OMZ microbial communities assemble and respond to environmental variation is therefore essential to understanding OMZ functioning and ocean biogeochemistry. Sampling along depth profiles at five stations in the eastern tropical North Pacific Ocean (ETNP), we captured systematic variations in dissolved oxygen (DO) and associated variables (nitrite, chlorophyll, and ammonium) with depth and between stations.