Sensitivity and Response to Thermal Stress in Palythoa caribaeorum

• Grant number: 24/06626-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2024
• End date: January 31, 2025
• Field of knowledge: Biological Sciences - Ecology - Ecosystems Ecology
• Principal Investigator: Miguel Mies
• Grantee: Mariana Ferreira Acipreste
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Coral reefs form diverse and productive ecosystems, providing important ecosystem services and holding significant ecological and economic importance. However, human activities are increasingly impacting coral reefs, such as rising ocean temperatures, leading to the phenomenon of coral bleaching, which currently affects reefs worldwide. The response to bleaching varies among regions and species, and Brazilian corals are known to be more tolerant compared to those in other regions. Among the cnidarian species found in Brazil, Palythoa caribaeorum stands out. This zoanthid is dominant in shallow rocky environments and has a wide geographical distribution due to its tolerance to various environmental conditions. Despite its economic and ecological importance, P. caribaeorum is currently experiencing bleaching in nature, particularly in Brazil, as evidenced by field observations. However, although some mechanisms of this process are well known through literature analysis, little is understood about how this species actually tolerates bleaching and what its thermal tolerance limits are. Therefore, this project aims to investigate the thermal stress response of P. caribaeorum through laboratory experiments, analyzing the content of chlorophyll-a and symbionts, bleaching, and apparent mortality. It is expected that alterations in its photosynthetic parameters will occur only after exposure to thermal stress values 6 degrees higher than the average temperature of occurrence in nature, indicating greater tolerance compared to scleractinian corals in general. Understanding how P. caribaeorum truly responds to bleaching and its thermal tolerance limits is essential for comprehending how these organisms would respond to the current scenario of climate change. This knowledge can then be used to predict the consequences for the surrounding diversity and habitat structure, serving as an important tool for environmental management.