Project: Linking infaunal hydraulic activities, porewater flow and biogeochemical processes in marine sediments

This research project is funded under the American Recovery and Reinvestment Act (ARRA) of 2009 (Public Law 111-5). In addition to being funded as part of the NSF Biological and Chemical Oceanography programs, the research is also related to the Ocean Drilling Program (ODP) and the Integrative Computing Education and Research (ICER) initiative.

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.

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.

Publications resulting from this research:
Woodin, SA; Wethey, DS; Volkenborn, N. "Infaunal Hydraulic Ecosystem Engineers: Cast of Characters and Impacts," INTEGRATIVE AND COMPARATIVE BIOLOGY, v.50, 2010, p. 176. DOI: 10.1093/icb/icq031

Volkenborn, N; Polerecky, L; Wethey, DS; Woodin, SA. "Oscillatory porewater bioadvection in marine sediments induced by hydraulic activities of Arenicola marina," LIMNOLOGY AND OCEANOGRAPHY, v.55, 2010, p. 1231. DOI: 10.4319/lo.2010.55.3.1231

Matsui G; Volkenborn N; Polerecky L; Henne U; Wethey D; Lovell CR; Woodin SA.. "Mechanical imitation of bidirectional bioadvection in aquatic sediments.," Limnology and Oceanography Methods, v.9, 2011, p. 84. DOI: 10.4319/lom.2011.9.84

Volkenborn, N, L Polerecky, DS Wethey, TH DeWitt, SA Woodin. "Oxic-anoxic oscillations around complex burrow structures caused by hydraulic activities of the ghost shrimp Neotrypaea californiensis.," Marine Ecology Progress Series, v.455, 2012, p. 141. DOI: 10.3354/meps09645

Woodin, SA, DS Wethey, JE Hewitt, SF Thrush. "Small scale terrestrial clay deposits on intertidal sand flats: behavioral changes and productivity reduction.," Journal of Experimental Marine Biology and Ecology, v.413, 2012, p. 184. DOI: 10.1016/j.jembe.2011.12.010