Research Topics:

I am interested in early diagenetic reactions and elemental cycling involving the decomposition of organic matter, dissolution of inorganic biogenic debris, and the mobilization -reprecipitation of metals sensitive to oxidation-reduction. These reactions are most intense and rapid in the upper meter, and especially in the upper few centimeters, of marine sediment. It is in this upper zone where most benthic organisms live and interact with sediments and where exchange of material between sediment and overlying water is largely determined. Knowledge of early diagenetic processes occurring in this zone is, therefore, essential for understanding elemental cycling in sediments and overlying water, certain ecological interactions and adaptations of marine organisms, and the long-term recording of historical information in marine deposits, for example, fossil preservation.

My students and I are currently studying diagenetic processes, mineral authigenesis, and exchange rates of dissolved material across the sediment-water interface in a variety of coastal and deep-sea marine areas, including Long Island Sound, French Guiana (Amazon – Guianas mobile mudbelt), and Papua New Guinea. One major part of our research involves the development and application of 2-dimensional optical sensors for examination of biogeochemical heterogeneity and dynamics in the complex bioturbated zone. For example, we have recently developed pH and pCO2 sensors which allow unprecedented resolution of biogeochemical reactions and solute transport patterns associated with biogenic structures. A second major emphasis of our research is on large scale diagenetic patterns related to physically energetic sedimentary facies (mobile mud belts) and authigenic mineral formation, particularly Fe-rich clays (reverse weathering) and Fe-carbonates, in tropical deltaic systems. These deltaic deposits contrast dramatically with bioturbated sediments and are dominated by physical mobilization of massive quantities of sedimentary debris. They are of extraordinary importance to elemental cycling and organic matter remineralization or storage globally.

We have collaborative projects with other SoMAS and SUNY faculty as well as with colleagues at other institutions, including Josephine Aller, J. Kirk Cochran, Cindy Lee, John Mak, Qingzhi Zhu, and Richard Reeder (Geosciences), Neal Blair (NCSU); Gregg Brunskill (AIMS, Townsville, AU), Frédéric Baltzer (Univ. Paris), Yanzhen Fan (OSU), Franck Gilbert (Univ. Marseilles), Stefan Hulth (Göteborg Univ.), Charles Nittrouer (Univ. Washington), and Donald Rhoads (Woods Hole). Several of our ongoing research projects are listed here:

1. Development and use of planar optode sensors for in situ (SPI hyperspectral camera system – Chem-SPI – collaboration with D.C. Rhoads) and 2-D laboratory microcosm measurement of solute, solid, and microbial enzyme activity distributions.
2. Organic matter remineralization, suboxic reactions, and rates and kinetics of authigenic mineral dissolution-precipitation (particularly Fe-rich clays (reverse weathering reactions), carbonates, sulfur, biogenic silica) in tropical deltaic mobile mud facies and their impact on global biogeochemical cycles.
3. Animal-sediment interactions, particularly biogeochemical, of macrobenthos living in soft-bottom regions of the sea floor.
4. Studies of diffusion coefficients and exoenzyme activity in biogenic mucoid secretions.
5. Effects of macrobenthic organisms on microbial metabolic activity and on the rate and distribution of biogenic and abiogenic reactions in the bioturbated zone of sediments.