EAPSI: Exploring the mysterious behavior of nitrogen cycling in seagrass ecosystems

Salk Kateri R, Okemos MI

Investigators

Abstract

Coastal environments today are receiving unprecedented amounts of nitrogen, an important nutrient that, in excess, results in nuisance algal blooms, oxygen deficiency, and fisheries collapse. Mitigation efforts will depend on an understanding of the natural pathways by which nitrogen is removed. This research will examine the environmental conditions that control two microbial nitrogen removal processes, denitrification and anammox. There are still many uncertainties concerning the environmental factors that control these processes in coastal ecosystems, as the anammox process has only recently been discovered and hypothesized to rival denitrification in its removal of nitrogen. These uncertainties will be addressed through a series of environmental monitoring and tracer experiments conducted in seagrass sediments in Australia. This work will be accomplished in collaboration with Dr. Dirk Erler, an expert in the field of coastal nitrogen cycling with access to unique analytical equipment and field sites at Southern Cross University. In particular, this research will investigate (a) the environmental conditions conducive for the production of the greenhouse gas, nitrous oxide, in systems where denitrification and anammox co-occur and (b) the role of organic carbon in determining the contributions of anammox and denitrification to nitrogen removal. Chambers will be installed on sediments in seagrass beds to enable in situ monitoring of denitrification, anammox, and nitrous oxide production rates. Isotopic tracers will be added to the incubations to track the formation of end products of nitrogen cycling processes by mass spectroscopy and mass spectrometry. These sediments will also be analyzed for a suite of environmental parameters that can be examined as possible controlling factors. Very little nitrogen cycling research has been conducted in seagrass ecosystems, so this study will provide novel insights into nitrogen removal processes and greenhouse gas production in this environment. This NSF EAPSI award is funded in collaboration with the Australian Academy of Science.