Calcification

• There are daily and monthly variations in skeletal growth processes which could distort the timing and magnitude of geochemical signals in corals.

• Calcification varies geographically (with latitude and in different oceanic settings).

• There are small-scale variations in calcification within and among coral colonies.

• Calcification may be habitat dependent (eg lagoons are heterogeneous; effects of groundwater discharge).

• Nutrient history may affect coral calcification and growth.

Inclusive records

• Isotopic (d18O, d13C) and elemental ratio (Sr/Ca, Mg/Ca, U/Ca) records can reproduce climate variability.

• Different environmental signals (eg salinity, SST) can be deconvolved using a multi-tracer approach.

• Fluorescence records faithfully record the timing and magnitude of runoff from major rivers (Burdekin, Sepik) in wet, tropical catchments.  There may be other sources of fluorescence, so this technique could be extended to document other important oceanic processes (eg upwelling).

• The effect of calcification processes on the recording of these signals may be a matter of scale.

Other

• Other coral genera may provide useful information eg massive corals other than Porites, soft corals, and giant clams, such as Tridacna.

• Three-dimensional reconstructions of oceanic processes could be gained by examining sclerosponges (thermocline dynamics) and deep-sea corals (intermediate / deep ocean water masses), in addition to shallow-water corals.

• Using a multi-proxy approach, a suite of climate information could be compiled at various temporal and spatial resolutions.

What are the gaps?

• Systematic testing of the reproducibility of proxy records from corals

• Cross-calibration comparisons of different types of coral records

• Do various life-stages / calcification processes of corals interfere with long-term reproducibility of coral records?

• Can we combine calcification models and inclusive records to reconstruct climate within the annual cycle?

• How are isotopes and trace elements incorporated into the skeleton?

• Do micro-environments and boundary-layer processes (hydrodynamics) affect the transfer of isotopes and trace elements from water to coral?