Unravelling the Pathways of Nitrogen Cycling in Permeable Sandy Sediments in Tropical Coastal Systems
Funding: ARC Discovery 2008-2010
Investigators: Isaac Santos, Bradley Eyre, Ronnie Glud
Background/ Summary
Marine sand beds and beaches were considered biogeochemical deserts until very recently. Most previous studies on benthic carbon and nitrogen cycling have focused on muddy sediments. The key difference between muddy and sandy sediments is their permeability, which allows water to flow through pore spaces between the sand grains. Flushing of porewaters results in a greater transport of oxygen and organic matter into the sediment, leading to mineralisation rates as high, or higher, than muddy sediments.
We are currently investigating carbon and nitrogen cycling in permeable coral reef sediments using a combination field and laboratory experiments. This project is using cutting edge field- and laboratory-based techniques, including stable isotope tracers, to gain insights into how sand sediments control the biogeochemistry (and thus ecology) of coral reef ecosystems. Seasonal field experiments are being conducted at Heron Island (Great Barrier Reef). We suspect that high primary production in nutrient-starved coral reef environments is supported by rapid organic matter recycling in these sediments (and associated nutrient release). As sands cover 70% of the world's coastal environments, biogeochemical processes in sands may be a major but overlooked factor controlling surface water quality. Our research focus on how porewater flushing in sands may be linked to the cycling or organic matter and ocean acidification.
Relevant Publications
Santos, I. R. and Eyre, B. D. 2011. Radon tracing of groundwater discharge into an Australian estuary surrounded by coastal acid sulphate soils. Journal of Hydrology (in press November 2010)
Santos, I. R., Tait, D., Erler, D. and Eyre, B. D. The breathing of a coal cay: tracing tidally-driven seawater recirculation in permeable coral reef sediments. Journal of Geophysical Research (in press). doi:10.1029/2010JC006510.
Glud, R. N. Eyre, B. D. and Pattern, N. 2008. Biogeochemical responses to coral mass-spawning on the Great Barrier Reef : Effects on respiration and primary production. Limnology and Oceanography 53, 1014-1024.
Eyre, B. D., Glud, R. N. and Pattern, N. 2008. Coral mass spawning - a natural large-scale nutrient enrichment experiment. Limnology and Oceanography 53, 997-1013.
Patten, N.L, Mitchell, J.G, Middelboe, M, Eyre, B. D., Seuront, L., Harrison, P.L. and Glud, R.N. 2008. Bacterial and viral dynamics during a mass coral spawning period on the Great Barrier Reef. Aquatic Microbial Ecology 50, 209-220.
Updated: 21 December 2010