Assessing coral nursery performance on reefs in Northeast Brazil under bleaching and anthropogenic pressures

Climate change and anthropogenic pressures are intensifying coral bleaching and threatening the persistence of tropical reef ecosystems worldwide. In this context, improving the placement of coral nurseries through environmental pre-assessment is a critical step in reef management and restoration planning. This study assessed long-term thermal stress patterns, anthropogenic pressures, and the performance of pilot coral nursery trees (CNTs) at Seixas Reef, an urban-adjacent reef system in Northeast Brazil. Bleaching risk was evaluated using sea surface temperature data (1985–2022) from NOAA Coral Reef Watch, including Degree Heating Weeks (DHW) and the number of consecutive days with temperatures ≥29 °C. Hydrodynamic conditions—wave climate, currents, and sediment transport—were simulated using the Coastal Modeling System (SMC-Brasil) to support CNT site selection. Anthropogenic pressures were characterized through field observations and vessel-use analysis. Two CNT models were deployed at selected sites and monitored for structural stability, biofouling, and coral fragment condition. Results reveal an increasing frequency of thermal stress events, with major DHW peaks in 1998, 2010, 2020, and 2022, and a seasonal window of elevated bleaching risk between February and May. Hydrodynamic modeling highlighted spatial contrasts in wave exposure and sediment dynamics that guided CNT placement. Field observations showed that CNTs remained structurally stable under seasonal forcing and supported coral fragment persistence, although biofilm and macroalgal development occurred. Overall, the study demonstrates the value of integrating thermal stress indicators and coastal hydrodynamic modeling as a pre-assessment framework for coral nursery site selection, offering transferable guidance for pilot-scale restoration initiatives in urbanized reef environments.