title: Autonomous Marine Robotic Technology Reveals an Expansive Benthic Bacterial Community Relevant to Regional Nitrogen Biogeochemistry.
abstract: Benthic accumulations of filamentous, mat-forming bacteria occur throughout the oceans where bisulfide mingles with oxygen or nitrate, providing key but poorly quantified linkages between elemental cycles of carbon, nitrogen and sulfur. Here we used the autonomous underwater vehicle Sentry to conduct a contiguous, 12.5 km photoimaging survey of sea-floor colonies of filamentous bacteria between 80 and 579 m water depth, spanning the continental shelf to the deep suboxic waters of the Santa Barbara Basin (SBB). The survey provided >31 000 images and revealed contiguous, white-colored bacterial colonization coating > ∼80% of the ocean floor and spanning over 1.6 km, between 487 and 523 m water depth. Based on their localization within the stratified waters of the SBB we hypothesize a dynamic and annular biogeochemical zonation by which the bacteria capitalize on periodic flushing events to accumulate and utilize nitrate. Oceanographic time series data bracket the imaging survey and indicate rapid and contemporaneous nitrate loss, while autonomous capture of microbial communities from the benthic boundary layer concurrent with imaging provides possible identities for the responsible bacteria. Based on these observations we explore the ecological context of such mats and their possible importance in the nitrogen cycle of the SBB.
authors.forename: David L
authors.initials: DL
authors.lastname: Valentine
authors.affiliation: Jackson School of Geosciences, University of Texas , Austin, Texas 78712, United States.
authors.forename: G Burch
authors.initials: GB
authors.lastname: Fisher
authors.affiliation: Australian Center for Field Robotics, University of Sydney , Sydney, Australia.
authors.forename: Oscar
authors.initials: O
authors.lastname: Pizarro
authors.affiliation: Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution , Woods Hole, Massachusetts 02543, United States.
authors.forename: Carl L
authors.initials: CL
authors.lastname: Kaiser
authors.affiliation: Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution , Woods Hole, Massachusetts 02543, United States.
authors.forename: Dana
authors.initials: D
authors.lastname: Yoerger
authors.affiliation: Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution , Woods Hole, Massachusetts 02543, United States.
authors.forename: John A
authors.initials: JA
authors.lastname: Breier
authors.affiliation: Interdepartmental Graduate Program in Marine Science, University of California , Santa Barbara, California 93106, United States.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Tarn