Using Corals for Proxy Temperature and Salinity

Why we can use corals for paleo-proxies Deposit annual high density/ low density bands which provides timescale (like tree rings) High density = winter Low density = summer Corals are very sensitive to changes in temperature, salinity, nutrients, These changes are reflected in the make-up of the coral’s skeleton Decreased/increased growth Changes in stable isotope ratios Nutrients trapped within coral skeleton

Basic coral anatomy Zooxanthellae CaCO3

Ca2+ Coral Calcification

Coral Drilling Pneumatic hand drill

Larger pneumatic drills Coral Drilling Larger pneumatic drills

Porites astreoides Diploria strigosa

𝐶𝑎𝑙𝑐𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 : χ 𝑐𝑚 𝑑 ×𝜌 𝑔 𝑐𝑚 3 =𝐺 ( 𝑔 𝑐𝑚 2 𝑑 )

Proxy SST Ca2+

How to use isotopic ratios for proxy SST Obtain annual CaCO3 samples Lazer ablation Digestions of annual CaCO3 deposits. Inductively coupled plasma mass spectrometry (ICPMS) Mg2+/Ca2+, Ba2+/ Ca2+, Sr2+/ Ca2+ Multiple linear regression SST = (X2+/Ca2+)m + b

Proxy SSS Ca2+

How δ18O reflects SSS P E Two major oxygen isotopes: 18O and 16O Controlled by evaporation (E) and precipitation (P) 18O 18O 16O 16O 18O 16O P E 16O 18O 16O 18O 16O 16O 18O 18O 18O 18O 18O 18O

Bleaching recorded in coral skeletons Nutrients recorded in coral skeletons

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