Eos, Transactions, American Geophysical Union Volume 87, Number 39, 26 September 2006

Climate signals in corals might instead originate in coral biologySeasonal cycles in the abundance of several trace elements can be seen in the skeletons of reef corals.These patterns are often attributed to seasonal variations in sea surface temperature or another physical parameter, which affects the uptake and incorporation of elements into the skeleton.Trends in these cycles provide highly resolved records of ocean temperature.Implicit in such methods is the assumption that physiological processes within the corals do not bias these records.Sinclair et al. questioned this assumption through their analysis of magnesium, strontium, and uranium abundances in reef and deep-sea corals.Noting that deep-sea corals should show no trends attributable to seasonality because they are shielded from sea-surface temperatures, the authors found a large inverse relationship between magnesium and uranium within deep-sea corals that was dependent on skeletal type.Reef corals exhibit similar, but smaller, inverse relationships between magnesium and uranium, suggesting that biological fractionation occurs in these corals.The authors hypothesized that seasonal cycles therefore derive from a variation in a biological parameter, not a physical one, and note that physiological disturbances have the potential to significantly affect the accuracy of environmental records.(Geophysical Research Letters,