Testing Cold-Water Coral Proxies for Ocean Temperature Through Culture Experiments

Scleractinian cold-water coral (CWC) skeletons are valuable paleoclimate archives because they are easily dated, are found across a broad geographic and depth range, and their geochemistry is sensitive to environmental variability. However, due to the difficulty of accessing living CWCs, lab-based calibrations of CWC proxies are rare. We conducted a set of experiments aimed at creating one of the first direct culture calibrations of paleotemperature proxies in CWC. We incubated individuals of Balanophyllia elegans, a cold-water coral native to the Pacific Northwest, to test this specie's reliability as a temperature proxy archive. Corals were collected and shipped from Friday Harbor Labs, San Juan Island, WA to St. Olaf College for culture experiments. We then grew these corals under five different controlled temperature conditions (n=6 corals per treatment) ranging from 6°C to 17°C, with equal temperature spacings. To ensure that we are able to separate new skeletal growth in our culture experiments from old skeletal growth that occurred naturally, we labeled coral skeletons using calcein and manganese at the beginning of the experiment. After the end of the 6 month experiment, we will compare the sensitivity of trace element ratios (including Li/Mg, Sr/Ca, and U/Ca) to the temperatures in which corals were grown using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).