Intan Suci Nurhati, Ph.D.   
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 Coral-based Study of the Regional Marine Environments

PI: Ed Boyle (MIT)


Our Project and Its Importance

The world is undergoing a transition from an unregulated marine environment to managed oceans. Sound management of marine resources requires knowledge of the consequences of our activities. One of CENSAM key premises is that sensor and models are keys in understanding how our actions affect marine environment. However, an important dimension to the sensing and modeling approach is historical context: how does the present state compare to when there was no significant human imprints? Sensors can tell us where we are, but their recent coverage can't tell how the environments have changed from their natural state over the past decades. Fortunately, there is a supplement available for modern observations and models: the historical record in geological archives. In particular, our region is blessed with an abundance of reef building corals. Coral secretes calcium carbonate over time with annual density marks analogous to tree-rings. The calcium carbonate crystals contain geochemical indicators of environmental properties such as heavy metals. Thus geochemical analysis of dated corals can provide histories of environmental changes prior to modern observational era.


Heavy Metals: Reconstructing the History of Environmental Lead in the Region

We reconstruct coral-based histories of Pb (lead), Pb isotopes, and Cd to assess the signatures of local sources and distal transport of anthropogenic metals in our nearby oceans, via a suite of living and fossil corals from Singapore and offshore sites in the central and eastern Indian Ocean (Fig.1-left). Previous works in the Atlantic Ocean show the fidelity of coral Pb and Pb isotope measurements to monitor the changing levels and sources of leaded-gasoline consumption in the U.S. and Europe (Fig.1-right). But how about marine Pb in our region that phased out leaded-gasoline consumption in recent years? To refine our understanding of past and present changes of anthropogenic Pb in the region, we complement our coral records with continuous Pb measurements in aerosol and seawater from Singapore.

Results from this work have been published in Lee et al. (2014) and Chen et al. (2014)



Figure 1: (Left) The study sites. (Right) Atlantic coral Pb records. Kelly et al. (2009).


Corals in a Changing Environment

The ecologically diverse coral reefs of Singapore and SE Asia experience increased environmental stresses over the past decades. We also utilize our coral collections to reconstruct changes in land-use change such as sedimentation (via coral Ba/Ca) and nutrient sources (via nitrogen isotopes). Here we are not only interested in how the environment has changed as reflected in coral skeletal geochemistry, but also  understanding long-term impacts of the changing environment on corals.

Working with: Jani Tanzil (NTU), Jong-Mi Lee and Rick Kayser (MIT), and Branwen Williams (Claremont College)