Evolution of Mg transporters may explain biological effects on coral skeletal proxies in geochemistry

Abstract

Abstract Corals have been used as geochemical proxies since the 1970's and they play prominent roles in paleoclimatology. However, it has not been well elucidated how minerals in seawater are transported and precipitated in aragonite coral skeleton. There are no foundational methods to differentiate and quantify biogenic and abiogenic effects during skeletal formation, thus it hampers corals from being fully reliable environmental proxies. In this study, we evaluated biological complexity by investigating how genes evolved over geologic time scales. Mg transporter of Acropora digitifera, Acropora hyacinthus and Acropora millepora showed high similarity to Mg transporter of vertebrates. On the other hand, Acropora palmata and Acropora tenuis did not show such a trend. The three types of corals that showed high similarity to vertebrates appeared on the earth less than one million years ago while the other two species showed ages older than three million years ago. This difference could be possibly triggered by an environmental change such as the availability of Mg ion in seawater (seawater [Mg]). Our result indicated a strong biogenic response (Mg transporter) to abiotic factors (seawater [Mg]). We suggest our approach to investigate gene evolution may guide us to identify the geochemical proxies with strong biological effects.