Title: Potential importance of diffuse hydrothermal fluid seepage in supporting life along deep sea fracture zones
Abstract: The input of deep crust- and mantle-derived energy compounds to seafloor environments is known to support localized hotspots of life at numerous hydrothermal vent and seep sites of the ocean floor. Far less is known about the role of these same energy sources in supporting life at “diffuse” flow settingss, where fluid flow occurs more gradually and over larger areas of the seafloor. This is in part because diffuse flow settings are more difficult to locate due to the absence of strong temperature or fluid geochemical anomalies or visually apparent hot spots of life. In this presentation, I will explore the possibility that crust- and mantle-derived energy inputs play an important, so far unrecognized, role in sustaining life in seismically active deep sea environments. I will discuss recently detected sediment porewater geochemical anomalies from the hydrothermally active Azores Plateau that indicate substantial input of deeply-sourced fluids to the seafloor. In addition, I will present research plans to investigate the sources of dissolved organic molecules in these sediments, and present strategies to investigate the potential stimulation of microorganisms and macrofauna by diffuse fluids in this otherwise energy-depleted deep sea setting. The research conducted as part of this project raises important questions with respect to the importance of chemosynthetic processes in supporting life on our planet and has potential implications for the study of life-generating and -sustaining processes in subsurface environments elsewhere in the universe.