Archaea mediating anaerobic methane oxidation are key in preventing methane produced in marine sediments from reaching the hydrosphere; however, a complete understanding of how microbial communities in natural settings respond to changes in the flux of methane remains largely uncharacterized. We investigate microbial communities in gas hydrate-bearing seafloor mounds at Storfjordrenna, offshore Svalbard in the high Arctic, where we identify distinct methane concentration profiles that include steady-state, recently-increasing subsurface diffusive flux, and active gas seepage. Populations of anaerobic methanotrophs and sulfate-reducing bacteria were highest at the seep site, while decreased community diversity was associated with a recent increase in methane influx. Despite high methane fluxes and methanotroph doubling times estimated at 5–9 months, microbial community responses were largely synchronous with the advancement of methane into shallower sediment horizons. Together, these provide a framework for interpreting subseafloor microbial responses to methane escape in a warming Arctic Ocean.

Herbivore-induced plant volatiles (HIPVs) from infested plants are exploited by parasitoid wasps as cues to search for host habitat. However, uninfested (intact) and infested plants are often intermingled in nature, and how volatiles released by intact plants affect host-searching behavior in natural habitats remains unknown. In a previous study, using a wind tunnel, we found that intact maize plants negatively influenced landing behavior of a parasitoid wasp, Cotesia kariyai (Hymenoptera: Braconidae), when they were placed downwind of infested plants. To determine whether intact plant volatiles affect host searching by C. kariyai, we collected volatiles from intact plants using a headspace volatile collection technique. In a wind tunnel, wasps landed less frequently on a green paper model treated with intact plant volatiles placed in front of an infested plant, than on a green paper model treated with the solvent, hexane. In a 4-arm olfactometer, wasps spent significantly less time in an arena containing mixed volatiles from intact and infested plants, compared to the same arena treated only with volatiles from infested plants. Both results indicate that intact plant volatiles re-direct host-searching behavior in C. kariyai females. Chemical analyses suggest differences in volatiles between intact and infested plants. In terms of parasitoid adaptations for effective searching for hosts in complex environments, aversive effects of intact plant volatiles may help C. kariyai to locate patches of infested plants.

Archaea mediating anaerobic methane oxidation are key in preventing methane produced in marine sediments from reaching the hydrosphere; however, a complete understanding of how microbial communities in natural settings respond to changes in methane flux remains largely uncharacterized. We investigate microbial communities in gas hydrate-bearing seafloor mounds at Storfjordrenna, offshore Svalbard in the high Arctic, where distinct methane flux regimes ranging from steady-state dynamics, recent increase in subsurface diffusive flux, and gas seepage were identified. Populations of anaerobic methanotrophs and sulfate-reducing bacteria were highest at the seep site, while a recent increase in methane influx was associated with decreased community diversity. Despite high methane fluxes and methanotroph doubling times estimated at 5-9 months, microbial community responses were largely synchronous with the advancement of methane into shallower sediment horizons. Together, these provide a framework for interpreting subseafloor microbial responses to methane escape in a changing Arctic.