Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements

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

Evaluation of trace elements released by edible clays in physicochemically simulated physiological media

Physicochemical simulation (pH, electrolytes and temperature) of three physiological media was carried out in order to follow the release of trace elements contained in seven edible clays (mainly kaolinite, illite, muscovite and quartz) collected from the West African countries of Cote d'Ivoire, Guinee and Senegal. These clays are ingested by pregnant women for diverse reasons that are related to their condition. Simulated oral (6.5pH7), stomach (pH approximately 1.8) and intestinal (pH approximately 8.3) media were prepared separately in order to compare the quantities of the trace elements released. Samples were analyzed by inductively coupled plasma emission spectrometry and spectrophotometry for the evaluation of copper, iron ((Fe(II) and Fe(III)), lead, manganese, nickel and zinc, since some of these elements can palliate deficiency problems and others can induce toxic effects. The quantities of the chemical elements released were pH dependent. The lower the pH, the higher the quantities of copper, Fe(III) and zinc. The quantities of Fe(II) were similar at both lower (stomach) and higher (intestinal) pH values. However, the quantities of manganese, nickel and lead were lower than quantification limits. Heating (110C) of the clays increased the quantities of trace elements released and could also participate in the microbiological 'decontamination' of raw materials. Microbiological analysis shows that all samples tested were in compliance with the recommendations of the European Pharmacopoeia. To verify the existence of possible beneficial and hazardous effects on human health, the quantities of copper, iron and zinc were compared with the recommended allowances for trace elements in France. In addition, the quantities of manganese, nickel and lead were compared with the maximum admissible concentrations in drinking water

PAGES Zaragoza 2017 : global challenges for our common future : a paleoscience perspective : abstract book

Marine calcifying organisms are under threat from global climate change. Ocean acidification (OA) and warming sea surface temperature (SST) are the results from increasing anthropogenic CO2 emissions. It is thus important to better understand how marine ecosystems and reef-building corals have responded to climate change pressures relative to historical pH and SST variability. To constrain the natural variability of pH and provide baseline reconstruction and quantification for OA, we measured delta 11B composition in an annually banded modern Diploastrea heliopora massive coral colony from New Caledonia in the southwestern Pacific. This coral displays uninterrupted growth between 1690-2010 CE covering historical periods from the termination of the Maunder Minimum (ca. 1690-1715 CE) through the beginning of the Industrial Revolution (ca. 1760-1830 CE) and into the modern era (1900 CE to present). The most striking feature from our pH reconstruction is the evidence of OA (decrease in sea surface pH) based on the depleting delta 11B ratio in the most recent portion of the record. The distinct trend of decreasing delta 13C ratio in this coral documents and confirms the Suess Effect due to increase in anthropogenic atmospheric CO2 concentration. This modern decrease in reconstructed pH is concurrent to the significant warming trend of at least 1 ºC as revealed by our coral-based SST proxies (i.e., Sr/Ca, Li/Mg, and delta 18O). The interannual and longer-term decadal to interdecadal variability of our proxy records indicate a coupled anti-phase relationship between pH and SST reflecting similar climatic drivers related to the El Niño/Southern Oscillation (ENSO) and Pacific Decadal Oscillation. Our results support the potential of this coral genus as an archive to study global climate change where the lower frequency variability of South Pacific pH and SST are strongly modulated by ENSO and are coherent with records across the greater Pacific basin

320 years of sea surface pH and SST variability in the South Pacific inferred from Diploastrea heliopora coral proxy records [résumé]

Marine calcifying organisms are under threat from global climate change. Ocean acidification (OA) and warming sea surface temperature (SST) are the results from increasing anthropogenic CO2 emissions. It is thus important to better understand how marine ecosystems and reef-building corals have responded to climate change pressures relative to historical pH and SST variability. To constrain the natural variability of pH and provide baseline reconstruction and quantification for OA, we measured delta 11B composition in an annually banded modern Diploastrea heliopora massive coral colony from New Caledonia in the southwestern Pacific. This coral displays uninterrupted growth between 1690-2010 CE covering historical periods from the termination of the Maunder Minimum (ca. 1690-1715 CE) through the beginning of the Industrial Revolution (ca. 1760-1830 CE) and into the modern era (1900 CE to present). The most striking feature from our pH reconstruction is the evidence of OA (decrease in sea surface pH) based on the depleting delta 11B ratio in the most recent portion of the record. The distinct trend of decreasing delta 13C ratio in this coral documents and confirms the Suess Effect due to increase in anthropogenic atmospheric CO2 concentration. This modern decrease in reconstructed pH is concurrent to the significant warming trend of at least 1 ºC as revealed by our coral-based SST proxies (i.e., Sr/Ca, Li/Mg, and delta 18O). The interannual and longer-term decadal to interdecadal variability of our proxy records indicate a coupled anti-phase relationship between pH and SST reflecting similar climatic drivers related to the El Niño/Southern Oscillation (ENSO) and Pacific Decadal Oscillation. Our results support the potential of this coral genus as an archive to study global climate change where the lower frequency variability of South Pacific pH and SST are strongly modulated by ENSO and are coherent with records across the greater Pacific basin

Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements

The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one 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 \u3c0.5°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