Aplicação de isótopos estáveis de carbono na avaliação da taxa de crescimento do coral Porites astreoides (Lamarck, 1816) do Atol das Rocas - Atlântico Sul

Abstract

Corals are often used as natural archives for climate research. These organisms have the ability to incorporate geochemical data into their exoskeletons, which can be used as proxies for different environmental variables. In this work, multiple carbon stable isotope profiles (δC) were used in different sections of a Porites astreoides (PTM-1) coral colony, collected at Rocas Atoll South Atlantic. This approach aims to verify the effectiveness of this method as an alternative for the evaluation of coral growth rate of the Scleractinia group. Such method is based on the idea that the coral δC varies according to the luminosity (i.e. cloud cover), which presents seasonal variability and leave the annual cycles recorded in the corals. Thus, the length of each isotopic cycle corresponds to the growth rate of a coral. In this work, 4 isotopic profiles with 0.5 mm sampling resolution were carried out. The δC cycles were used to evaluate the growth rate of the PTM-1 colony. The length of the δC cycles varied from 3 to 12 mm along the profiles and the overall average growth rate estimated for this colony was 6.69 ± 2.39 mm/year, close to those reported for this species in other species. regions, indicating the effectiveness of this method in assessing coral growth rate.