Cecile Rousseaux
Cecile Rousseaux’s project is based at Ningaloo Reef, where she is studying the effects of the Leeuwin current on the reef’s ecology and biogeochemistry.
The research is based on the production and transport of particles in a regional current system adjacent to a fringing coral reef.
Cecile is from Belgium and holds a BScHons (First class, 2005) and MSc (First class, 2006). She began her PhD at The University of Western Australia in 2007.
Recent studies suggest that reefs rely on particles flowing in from the ocean to sustain their high productivity.
Her work involved two major field investigations looking at the biological variables off Sandy Bay in Cape Range National Park. Profiles of physical parameters, primary productivity, particulate matter, nutrient uptake rates and phytoplankton abundance and diversity were sampled along an 18-kilometre transect in June and November 2008.
Analysis suggests that the phytoplankton concentrations are higher in May (maximum of 0.8 µg/l) than in November (maximum of 0.3 µg/l). The bloom observed in May was mainly represented by diatoms. The data suggests that the new production peaks in autumn because of the acceleration of the Leeuwin Current and not in summer during the upwelling season, as had been expected.
Seawifs data shows that the development of this bloom in May-June has been consistent during the past five years (2003-2008). The geostrophic volume transport of the Leeuwin Current is lower during El Niño than during La Niña conditions (1). Our data suggests that during period of high Leeuwin Current flow a bloom of large (>5μm) phytoplankton develops off Ningaloo. This is likely to impact/feed the reef through the cross-shelf transport of these particles. Feng et al. (2003) have also shown the volume transported by the Leeuwin Current is lower during El Niño than La Niña years. Several studies have noted that the pattern of El Niño ± Southern Oscillation (ENSO) variability changed in 1976, with warm (El Niño) events becoming more frequent and more intense (2, 3). If the frequency of El Niño events increases with climate change, the occurrence of these bloom-events off Ningaloo Reef may decrease in frequency and pose the reef with a serious threat.
Cecile’s research covers WAMSI Node 1 and 3 projects. She has also received a BHP Billiton scholarship. Her supervisors are Professor Anya Waite, Dr Peter A. Thompson and Dr Ryan Lowe.
References
1. Feng, M., G. Meyers, A. Pearce, and S. Wijffels. 2003. Annual and interannual variations of the Leeuwin Current at 32 S. J. Geophys. Res 108: 3355.
2. Guilderson, T. P., and D. P. Schrag. 1998. Abrupt Shift in Subsurface Temperatures in the Tropical Pacific Associated with Changes in El Niño. Science 281: 240.
3. Dai, A., K. E. Trenberth, and T. R. Karl. 1998. Global Variations in Droughts and Wet Spells: 1900-1995. Geophysical Research Letters 25: 3367-3370.