This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Most of the oceanic seafloor is pervaded by burrows and tubes of infauna. Activities of these animals, such as burrowing, feeding, and defecation, are of fundamental importance to biogeochemical processes as these activities are associated with movement of sediment porewater. These bio-advective processes increase benthic-pelagic coupling and microbial activity, but the underlying mechanisms by which infaunal activities drive biogeochemical cycling through bio-advection are very poorly understood. Recent work has demonstrated that bio-advection is the result of behavior specific, hydraulically generated pressure fields with changing directions and radial extent from the burrow of 50 cm or more. These results force a re-evaluation of sediments as habitats with transient conditions predominant to the depth of biotic activity. This project addresses (a) which types of infauna contribute significantly to these bio-advective processes, (b) what behaviors generate porewater fluxes, how frequently and under what conditions, (c) what is the impact on oxygen availability within the sediment and how transient is this availability, (d) what is the impact on biogeochemical rates and microbial community structure, and (e) what are the direct effects and feedbacks on biological processes, such as primary productivity and recruitment?
The general goals are to determine the influence of large, numerically dominant polychaetes, bivalves, and crustaceans on bio-advective porewater flow and its consequences for biogeochemical cycling and feedbacks on the benthic community. First, using a combination of field and laboratory measurements, the research will analyze the diversity of hydraulic activities by important large infauna to determine which types of infauna contribute most significantly to these bio-advective processes and what behaviors are the most important to porewater flux. Second, laboratory experiments will link species-specific hydraulic activities to chemocline dynamics using live animals and biomimetic 'robolugs' to produce controlled porewater flows. For selected hydraulic behaviors the impact on microbial activity and diversity will be analyzed. Finally, feedback mechanisms on benthic communities in habitats that they partly create will be analyzed using a combination of large laboratory aquaria and field deployed robolugs.
Intellectual Merit: This research challenges the traditional view that most sediments are primarily steady-state, diffusion-dominated systems. The research will be transformative to the fields of benthic ecology, microbial ecology, and biogeochemistry as it makes obvious the central role played by infaunal animals in driving changes in the chemical and physical properties of sediments.
Broader Impacts: Two postdoctoral fellows will take part in this project and will receive training in research, mentoring of graduate and undergraduate students, scientific integrity, and career preparation. This project will also engage undergraduate students who will participate in weekly lab meetings, do research designed in part by them and meet weekly one-on-one with their mentor PI. All will be encouraged to present posters at national meetings. During the summer these students will participate in the Biology REU program, which has weekly meetings about research ethics, publishing scientific papers, applying to grad school, and strategies for success in grad school. To expose pre-college students to the excitement of interdisciplinary research and increase hands-on participation in science by students and teachers, the research team will participate in the SCience Lab program run by Dr. Bert Ely, Director of the Center for Science Education and funded in part by NIH. Middle school students will come to USC to do a research exercise that meets the state science standards and that can be completed between 9:30 am and 1:30 pm. An exercise using the robolugs will demonstrate the impact of organisms on sediments.
