IDEAUS - CENPAT   25626
INSTITUTO DE DIVERSIDAD Y EVOLUCION AUSTRAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Characterization of a CO2 vent in La Palma (canary islands) and its effects on the calcified structures of Arbacia lixula
Autor/es:
HERNÁNDEZ, J.C.; EPHERRA, L.; GONZÁLEZ-DELGADO, S.; HERNÁNDEZ, C.A.; ALFONSO, B.
Lugar:
Nagoya
Reunión:
Conferencia; 16th International Echinoderm Conference; 2018
Institución organizadora:
Nagoya University
Resumen:
The seawater absorption of anthropogenic CO2 is causing the ocean acidification (OA), a decrease of the mean surface ocean pH. Current ocean pH is about 8.07 and a decrease of about 0.3 ? 0.5 pH units is expected for the end of the century. OA especially affects calcifying organisms, decreasing the aragonite and calcite saturation states in seawater, suppressing calcification and even causing the dissolution of their structures.Natural CO2 vents add carbon dioxide to seawater, producing a decrease in pH in a similar way to how OA does, making these vents useful tools to take a sneak peek at the oceans of the future. There is such a CO2 vent in Fuencaliente (La Palma, Canary Islands), with pH levels similar to those predicted for the end of the century. Equinoids are interesting research subjects for ocean acidification studies due to their calcite structures and great plasticity. I this study we analysed some population parameters and the calcified structures of the sea urchin Arbacia lixula in a pH gradient caused by the aforementioned vent area. We chose three study zones along the vent: CO2 seep (pH=7.6), transition zone (pH=7.8) and control zone (pH=8.1). At each zone, 35 sea urchins were collected. The morphological variability of the calcium carbonate structures was then analysed: diameter and width of the body, length and width of the spines and size of the Aristotle?s lantern. The force necessary to break the shells was also assessed. To study the crystallographic structure and composition of the calcium carbonate phase forming these structures, X ray diffraction and EDX (energy-dispersive X-ray spectroscopy) measurements were performed for each of them.The individuals with smaller diameters and shorter spines were detected in the vent area. However, more force had to be applied to break their tests. These results suggest that, despite been located in a low Ωcalcite environment, A. lixula is able to form harder shells, although decreasing the length and width of its spines. On the other hand, the ratio between the Aristotle?s lantern and the sea urchin diameter did not significantly vary between zones, suggesting that this species? diet could be similar at the different studied vent zones. These results suggest that, under the same feeding conditions, A. lixula invests more energy in forming harder shells when subject to less alkaline conditions that can impede calcification. XRD patterns showed that the calcium carbonate structures of A. lixula are formed by magnesium calcite. No significant differences were detected in the crystalline structure of this crystalline phase between the different vent zones. EDX analyses showed that Mg content was less than 4% in this magnesian calcite.