气候变化领域集成服务门户

High-latitude cold-water coral reefs are particularly vulnerable to climate change due to enhanced CO2 uptake in these regions. To evaluate their physiological functioning and potential application as pH archives, we retrieved both recent and fossil samples of Lophelia pertusa along the Norwegian margin from Oslofjord (59 degrees N), over to Trondheimsfjord, Sula and Lopphavet (70.6 degrees N). Boron isotope analyses (delta B-11) were undertaken using solution-based and laser ablation multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS; LA-ICP-MS), and secondary ion mass spectrometry (SIMS). Epi-fluorescence microscopy was employed to provide a rapid pre-screening routine for structure-specific subsampling in the coral skeleton. This integrated approach enabled us to assess heterogeneities within single specimens, as well as to investigate the role of local environmental influences including recent and past variations. All three mass spectrometry methods show substantial differences in the delta B-11 of the theca wall (TW) and the centres of calcification (COC's). Micro-bulk subsamples milled from the theca wall of modern specimens originating from different habitats but with comparable seawater pH (8-8.16) gave consistent delta B-11 values averaging 26.7 (+/- 0.2 parts per thousand, 2 sigma, n = 4), while COC subsamples systematically deviated towards lower B/Ca (by similar to 40%) and depleted delta B-11 values (minimum 22.7 +/- 0.3 parts per thousand, 2 sigma), implying a difference of at least 4 parts per thousand between TW and COC. SIMS and LA-ICP-MS measurements identified much larger internal heterogeneities with maximum variation of similar to 10 parts per thousand between the distinct skeletal structures; minimal SIMS delta B-11 values of similar to 17.3 +/- 1.2 parts per thousand (2 sigma) were associated with the pure COC material. Our findings may be interpreted in terms of the occurrence of two main, but likely different, biomineralisation mechanisms in L. pertusa, with the COC's generally exhibiting minimal pH up-regulation, potentially supporting the use of bicarbonate in the early stages of biomineralisation. Furthermore, we highlight the potential utility of L. pertusa for palaeo-proxy studies if targeting the compositionally homogenous TW zones devoid of COC admixtures, which appear to provide highly reproducible measurements.