Uncovering the patterns and mechanisms of environmental memory in the Brazilian endemic reef coral, Mussismilia hispida

• Grant number: 24/14780-2
• Support Opportunities: Scholarships in Brazil - Support Program for Fixating Young Doctors
• Effective date (Start): September 01, 2024
• Effective date (End): August 31, 2025
• Field of knowledge: Biological Sciences - Ecology - Applied Ecology
• Acordo de Cooperação: CNPq
• Principal Investigator: Ronaldo Bastos Francini Filho
• Grantee: Andreia Cristina Barbosa de Oliveira
• Host Institution: Centro de Biologia Marinha (CEBIMAR). Universidade de São Paulo (USP). São Sebastião , SP, Brazil
• Associated research grant: 24/02182-3 - Uncovering the patterns and mechanisms of environmental memory in an endemic Brazilian coral, Mussismilia hispida, AP.R

Abstract

Currently, climate change represents the main threat to the health and survival of coral reefs. Elevated temperatures for prolonged periods, together with intense solar radiation, cause oxidative stress and trigger mass bleaching events, i.e. the breakdown in the symbiotic relationship between the host coral and its photosynthetic endosymbionts. As the frequency and intensity of marine heat waves increases, coral bleaching and mass mortality events become increasingly frequent and severe. However, evidence of reduced incidence and/or severity of bleaching following recurrent marine heatwaves highlights the increase in resilience gained by corals through previous exposures to thermal stress. This phenomenon can be attributed to environmental memory, a mechanism that allows organisms to present a modified response to a specific stress when preceded by a sublethal exposure to the same (or another) stress. Indeed, coral communities previously exposed to heat waves have shown a lower propensity to bleaching in the Caribbean, the Great Barrier Reef and the Indo-Pacific. However, reduction in damage severity was observed in successive annual bleaching events following heat waves, but not in events separated by more than two years, especially when thermal stress was more severe during the second event. On the other hand, the increase in thermal tolerance resulting from environmental memory acquired after exposure to high solar radiation can be 'remembered' by corals for up to a decade. The effects of previous exposure to combined stressors, such as high solar radiation and high temperature, await evaluation in the context of environmental memory in corals. Turbid reefs, such as those found in the Southwest Atlantic, are particularly recognized as an important climate refuge for corals, as the turbidity provides a natural shield against high solar radiation during heat waves. Brazilian reef ecosystems extend over approximately 3,000 km from equatorial to subtropical latitudes. Within the same latitudinal range and across gradients from the coast to the sea (cross shelf), marked decreases in turbidity levels are generally noted, which influences the composition and structure of benthic communities. On a more localized scale, significant differences between shallow reefs (warmer waters and well-lit) and deeper reefs (colder waters and low light) can influence the structure of the benthic community. Therefore, these systems exhibit a wide variety of environmental conditions, presenting a unique opportunity to study how local environmental factors can shape coral adaptive responses. Clearly, additional studies are needed to identify populations of Brazilian corals that show greater resistance/resilience to bleaching, as well as to understand environmental memory patterns in these corals, as the results have important implications for the development of conservation strategies, such as prioritizing protection of climate refuges and for restoration initiatives. (AU)