[1] The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twentyone laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7 C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5 C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5 C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

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The Eastern Lau Spreading Center (ELSC) is the southernmost part of the back-arc spreading axis in the Lau Basin, west of the Tonga trench and the active Tofua volcanic arc.Over its 397-km length it exhibits large and systematic changes in spreading rate, magmatic/tectonic processes, and proximity to the volcanic arc. In 2005 we collected 81 samples of vent water from six hydrothermal fields along the ELSC. The chemistry of these waters varies both within and between vent fields, in response to changes in substrate composition, temperature and pressure, pH, water/rock ratio, and input from magmatic gases and subducted sediment. Hot-spring temperatures range from 229º to 363ºC at the five northernmost fields, with a general decrease to the south that is reversed at the Mariner field. The southernmost field, Vai Lili, emitted water at up to 334C in 1989 but had a maximum venting temperature of only

Most fish otoliths are composed of aragonite, but occasionally they form a mosaic with its polymorph, vaterite. We found an unusual mosaic structure of extremely low strontium to calcium (Sr/Ca) ratio in the aragonite otoliths of European eels Anguilla anguilla. The mosaic crystal structure in the eel otolith appeared opaque under reflected light after EDTA etching and was confirmed to be a vaterite crystal by Raman spectroscopy. Analysis by laser ablation inductively coupled plasma mass spectrometry indicated that the elements sodium (Na), strontium (Sr) and barium (Ba) were lower in abundance and magnesium (Mg) and manganese (Mn) were higher in the vaterite than in the aragonite. Otoliths with vaterite inclusions were found in 48.1% of the 108 eels examined. If the mosaic vaterite in otoliths is not identified and avoided, the migratory environmental history of fish could be misidentified when otolith elemental signatures are used as biological tracers.