Organic matter remineralization in coastal sediments in and around Kane‘ohe Bay, Hawaiʻi

Abstract

Nutrient cycles in shallow, near shore environments can be profoundly influenced by sediments, via the burial or release of nutrients through organic matter (OM) remineralization during diagenesis. The decomposition and burial of OM in sediments are key processes influencing biogeochemical cycles of nutrients (nitrogen, phosphorus) and carbon in coastal waters on time scales ranging from seasonal fluctuations to long, geologic timescales. This dissertation examines several aspects of OM remineralization in marine sediments, and addresses fundamental questions that link organic matter source, sediment redox state, and nutrient cycling. The studies described in this dissertation include development of new techniques that permit quantification and characterization of OM sources to marine sediments, which will be informative for OM preservation studies (Chapters 2-3); in the latter portion of this dissertation (Chapters 3-6), particular aspects of early diagenetic pathways of OM remineralization are examined. The studies described herein place constraints on sources and sinks of bioavailable nutrients in coastal sediments, including the flux of nutrients at the sediment-water interface. As such, the processes examined throughout this dissertation are essential to understanding coastal ocean biological productivity, and can shed light on transport of bioavailable nutrients from coastal waters to the open ocean. The research presented here was conducted in and around coastal Kane'ohe Bay and, as such, reveals processes that may be unique to coastal systems adjacent to new, volcanogenic islands. However, many of the processes studied are more broadly operant, and insights into processes occurring within the coastal sediments of our study site can be readily extrapolated to other coastal systems.