Topic: Impact of ocean acidification on sediment-dwelling marine calcifiers
Supervisors: Assoc Prof Peter Ralph, Dr Ross Hill and Dr Martina Doblin (UTS)
PhD conferred: 2013
This project has been developed to examine how climate change will affect growth, calcification and photosynthesis in the calcifying marine algae Halimeda and benthic foraminifera. Increases in human activities, such as the burning of fossil fuels, industrialization, and agricultural practices have increased the concentration of carbon dioxide (CO2) in the atmosphere. This has lead to an increase in global temperatures through the trapping of heat through the Greenhouse Effect. CO2 from the atmosphere is dissolving into the oceans which results in the lowering of seawater pH (ocean acidification) and consequently decreases the availability of carbonate ions (CO32-). These CO32- ions are essential for the construction of calcium carbonate structures by organisms such as Halimeda and foraminifera and their reduction is expected to reduce the rate of calcification. In addition, the dissolution of calcium carbonate will increase as a result of decrease in its saturation states and the low rates of calcium carbonate precipitation. The calcification rate is also influenced by temperature, and while some studies have found that increasing temperatures will enhance calcification, other studies have shown that the thermal limits of marine calcifiers are being exceeded.
Reef building species, Halimeda and foraminifera, play a vital role in tropical and sub-tropical ecosystems, producing 1 kg CaCO3 m-2 y-1 and on some reefs contribute up to 90% of the sediment. Saturation states for aragonite (form of calcium carbonate in Halimeda and coral) are lower than those for calcite (form of calcium carbonate in foraminifera and coccolithophores). Thus, there might be differences between Halimeda and foraminifera in the response to elevated CO2 condition.Temperature and CO2 conditions will be manipulated in a series of experiments to simulate multiple future climate change scenarios.
The objectives of this project are to:
- Assess how calcification and photosynthesis will be affected in these ecologically important species.
- Provide a better understanding of the impacts climate change on reef ecosystems and to improve our predictive capacity of potential changes into the next century.
- Provide information that will help guide managers in developing strategies to deal with global climate change.
Warmer more acidic conditions cause decreased productivity and calcification in subtropical coral reef sediment-dwelling calcifiers
Sutinee Sinutok, Ross Hill, Martina A. Doblin, Richard Wuhrer, and Peter J. Ralph, Limnol. Oceanogr., 56(4), 2011, 1200–1212
Microenvironmental changes support evidence of photosynthesis and calcification inhibition in Halimeda under ocean acidification and warming
S. Sinutok, R. Hill, M. A. Doblin M. Kuhl and P. J. Ralph
Coral Reefs DOI 10.1007/s00338-012-0952-6
Sutinee in the news:
C3 research gives first insight into the microenvironment of climate change (Nov 2012)
Warmer more acidic oceans: a double whammy for sediment dwellers (May 2011)
C3 PhD coral reef research rewarded (January 2010)