Changes in the symbiotic dinoflagellate and GFP‑like protein in heat stress tolerant Porites harrisoni versus heat stress sensitive Acropora downingi: a case study in the Persian Gulf

Abstract

Coral reefs are among the most productive and diverse biological ecosystems in the world, hosting more than a quarter of all marine species. The coral reefs in the Persian Gulf, a sea surrounded by arid lands with high air temperatures, intense light, and high salinity of water, along with a remarkably large annual cycle of sea surface temperatures (SST), persist under challenging environmental conditions. The present study explored the changes in the symbiotic dinoflagellate and GFP-like proteins in a heat stress tolerant submassive Porites corals versus heat stress sensitive tabular Acropora corals across seasonal and depth gradients in Kish Island in the Persian Gulf. The results revealed that the symbiosis types was constant in both species, depth, and sampling seasons. However, an explicit change was observed in the quantity of symbiotic algae and Durusdinium trenchii as a heat-tolerant symbiodiniaceae dominating both coral species. Likewise, the level of GFP-like Protein mRNA expression, especially in P. harrisoni, significantly varied across seasonal and depth gradients. The GFP-like Protein mRNA was upregulated during summer in both species and decreased in P. harrisoni inhabiting the deep reef. Overall, the findings suggest that simultaneous changes in the symbiotic dinoflagellate and GFP-like proteins may be the key factors underlying the resistance of scleractinian corals during warm episodes in the Persian Gulf as the world’s warmest sea.