From Cane to Coral Reefs: Ecosystem Connectivity and Downstream Responses to Land Use Intensification • back to student info Stacey Jupiter, Stuart Phinn*, Norm Duke**, Don Potts*** *Biophysical Remote Sensing Group, The University of Queensland **Marine Botany, Centre for Marine Studies, The University of Queensland Brisbane, Australia 4072 ***Department of Ecology and Evolutionary Biology, University of California-Santa Cruz, USA commenced: May 2003 completed in June 2006 jupiter@biology.ucsc.edu

In tropical river catchments in Queensland, increasing rates and intensity of land use change are being expressed as greater exports of sediments and nutrients to nearby coastal and marine ecosystems. In many catchments, increased sediment/ nutrient export over the past half century is associated with a net loss of mangrove, and mangrove loss is now central to concerns about the health of adjacent marine ecosystems. Several models conclude that sediment delivery rates to the Great Barrier Reef lagoon have increased 2-6 fold since European settlement in the 19th century (Moss et al. 1992; Neil et al. 2002), but the roles and magnitudes of mangroves as buffers of sediments, nutrients and chemical exports to nearshore coral reef systems are virtually unknown. I am working in the Pioneer River estuary (at ~21oS) to determine whether historical records of changes in mangrove distribution are correlated with changes in chemical and isotopic proxies of suspended sediment concentration obtained from coral cores taken from nearshore colonies. The Pioneer system was selected as a study site for three main reasons: high sediment export, a net loss of mangroves through time, and a recent mangrove dieback described as the “worst of its kind in the world” (Duke et al. 2001). The main prediction is that mangrove loss has reduced entrapment of recent sediments, nutrients and pollutants, while increasing erosion has mobilized older estuarine sediments, nutrients and pollutants; both processes are likely to be manifested as increased incorporation of trace elements (e.g. barium, rare earth elements, high-field-strength elements) into coral skeletons at levels above those due to runoff alone. I am using remote sensing, ground surveys, and laboratory analyses in a three-phased approach to evaluate: (1) mangrove changes through time; (2) export of estuarine sediments; and (3) incorporation of sediments into coral skeletons. References Duke, N.C., Roelfsema, C., Tracey, D. and Godson, L.M. (2001) Preliminary Investigation into Dieback of Mangroves in the Mackay Region. Marine Botany Group, University of Queensland, St. Lucia. Moss, A.J., Rayment, G.E. , Reilly, N. and E.K. Best (1992) A preliminary assessment of sediment and nutrient exports from Queensland coastal catchments. Queensland Department of Environment and Heritage Technical Report No. 5, Queensland Government, Brisbane, 28 pp. Neil, D.T., Orpin, A.R., Ridd, P.V. and B. Yu (2002) Sediment yield and impacts from river catchments to the Great Barrier Reef lagoon. Mar. & Fres. Res., 53: 733-752.