subseafloor imageResearch

Coastal Benthic Boundary Layer

Interactions between physical, chemical, and biological processes are abundantly evident in the commercially-relevant coastal zone. We use a combination of traditional geochemical techniques and cutting-edge electrochemical techniques to study fundamental biogeochemical cycling of redox-reactive chemical species coupled to nutrient and carbon dynamics at the sediment-water interface in two important nearshore habitats: (i) low-physical-energy muddy sediments, and (ii) high-physical-energy permeable reef sediments. The upper layers of nearshore permeable sediments are dynamic, active sites of intense redox cycling. Previous research and our preliminary results indicate that vertical redox oscillations in these sediments can be driven by biogeochemical or physical variability, or by episodic events such as severe storms and their associated terrestrial runoff. Further, it can be assumed that each of these forcings operate on different and distinctive time and vertical scales.

Kilo Nalo graphics We are currently focused on rigorous estimations of biogeochemical fluxes across the hyperactive sediment-water interface (SWI) of permeable sediments, and within the upper 10cm of the sediment, by coupling porewater velocity modeling with fine-scale real time physical (temperature across the SWI, and sediment ripple topography) and chemical measurements (in situ voltammetry, pH and Eh profiles). The research couples cutting-edge in situ, fine-scale chemical and physical sensors, seafloor observatory infrastructure and data handling, and pioneering numerical models of porewater motion. This highly interdisciplinary approach aims to provide detailed information on the role that permeable sediments play in biogeochemical cycles of nearshore sediments, and to elucidate the processes that modulate permeable sediment functioning.

Support for our coastal biogeochemistry research has been provided by the National Science Foundation (OCE06-48637, OCE-1031947) and the University of Hawaii Sea Grant Program, as well as through various leveraged support of collaborators and the Kilo Nalu Nearshore Reef Observatory..

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