Two biomarkers of gene expression plasticity in Pocillopora corals from the Carrizales reef, Mexican Tropical Pacific

Abstract

Background. Gene expression (GE) plasticity is an acclimation response that allows organisms to adjust rapidly to environmental changes, providing an adaptive advantage. GE biomarkers are emerging as a valua-ble tool for linking the organism’s physiological plasticitywith the synergetic effects of large-scale climatic conditions and local impacts such as temperature and nutrients. Objectives. In this study, we investigate the GE plasticity of the 70-kDa heat shock protein (hsp70) and the carbonic anhydrase enzyme (CA) to confirm the ability of those two genes as biomarkers of the Cellular Stress Response and Cellular Homeostasis Res-ponse, respectively. Methods. Using qPCR, we evaluate the GE plasticity of coral colonies from Pocillopora capitata, Pocillopora damicornis,and Pocillopora verrucosa at the Carrizales reef (Colima coast of Mexico) naturally exposed to environmental changes in the Sea Surface Temperature (SST), productivity and nutrients using the cellular density of Symbiodiniaceae and chlorophyll content as health indices. Results. Our results clearly show GE plasticity in the hsp70 for Pocillopora verrucosa and Pocillopora damicornis related to a daily environmental change in temperature and nutrients. On the other hand, the CA gene expression shows no change in response to daily variations. However, there was a significantly high expression of CA and a lower expression of hsp70 in Pocillopora capitata. Furthermore, we found no significant differences in the health in-dices, suggesting some degree of physiological plasticity in Pocillopora corals like its extensive morphological plasticity that could reflect different adaptation capacities to low temperatures and high nutrients during the spring season in the central Mexican Pacific. Conclusions. Evaluating the phenotypic plasticity (morphology and molecular physiology) could help identify coral colonies with a more significant potential to survive en-vironmental stressors. The latter is an essential consideration for managing, conserving, and restoring coral reefs in the Mexican Pacific.