Abstract
Dissolved oxygen (DO) is often used as a water quality indicator and proxy for ecosystem health. Organic matter is remineralized in sediments by microbial and macrofaunal communities that consume DO in the process. DO consumption rate depends on the DO concentration of the overlying water but can also be enhanced by mixing and irrigating activities of sediment macroinfauna. DO in shallow coastal systems frequently exhibits a diel cycle, caused by photosynthesis increasing DO during the day and respiration drawing down DO at night. These recurring nightly drops in DO concentration may induce changes in DO consumption rates and macrofaunal behavior that affect total sediment oxygen consumption in unique patterns throughout the day/night cycle, and in different ways depending on the particular behavioral responses of macrofaunal taxa. However, most estimates of sediment metabolism are based on only a few DO consumption measurements, sometimes just one per day. If sediment DO consumption varies considerably throughout a diel cycle, current descriptions of sediment metabolism that use such limited measurements may be misestimating net metabolism rates, and therefore ecosystem health and function, over time. In this study, we addressed the questions, 1) do sediment DO consumption rates vary significantly over a diel cycle?, and 2) what influence do macrofauna have on sediment DO consumption throughout the diel cycle? We constructed in situ flow-through benthic metabolism chambers capable of producing a high temporal resolution time series of DO consumption associated with discrete patches of sediment and deployed them in shallow water off the Alabama coast. This research will enable better understanding of the connection between oxygen concentration and oxygen consumption, and improve our understanding of the role of macrofauna in modulating that relationship. Equipped with this knowledge, resource managers will be able to better track shifts in shallow marine ecosystem functioning and health.
