Drivers of coral bleaching in a Marine Protected Area of the Southern Gulf of Mexico during the 2015 event

Highlights: • 2015 was an unprecedented heat stress event with low coral bleaching in the area. • Depth best predicts bleaching with higher affectation in deeper reefs. • Coral reefs with high species richness and functionality were more susceptible. • Thermal metrics with a 28-days window are relevant thermal indicators. Here we report the bleached coral cover and its drivers observed at Alacranes Reef in 2015. Our results show that 2015 was an unprecedented heat stress event. However, we observed low coral bleaching, with the most substantial impact on sites with a 10–20% of coral cover with bleaching. Depth was the most relevant variable related to coral bleaching and the bleaching severity index, with deeper reefs being most affected. Further, our results show that reefs with higher structural complexity based on species composition were among the most affected. We identified that accumulated heat stress and thermal variation in the last 28 days were relevant drivers of coral bleaching. This work highlights the importance of multidimensional frameworks in assessing the spatial variation of coral bleaching, demonstrating the importance of structural habitat variables such as depth in high heat stress events and at a reef scale.