Impact of marine heatwaves for sea turtle nest temperatures

There are major concerns about the ecological impact of extreme weather events. In the oceans, marine heatwaves (MHWs) are an increasing threat causing, for example, recent devastation to coral reefs around the world. We show that these impacts extend to adjacent terrestrial systems and could negatively affect the breeding of endangered species. We demonstrate that during an MHW that resulted in major coral bleaching and mortality in a large, remote marine protected area, anomalously warm temperatures also occurred on sea turtle nesting beaches. Granger causality testing showed that variations in sea surface temperature strongly influenced sand temperatures on beaches. We estimate that the warm conditions on both coral reefs and sandy beaches during the MHW were unprecedented in the last 70 years. Model predictions suggest that the most extreme female-biased hatchling sex ratio and the lowest hatchling survival in nests in the last 70 years both occurred during the heatwave. Our work shows that predicted increases in the frequency and intensity of MHWs will likely have growing impacts on sea turtle nesting beaches as well as other terrestrial coastal environments.

Automated summary

Extreme weather events, such as marine heatwaves, have detrimental effects on marine ecosystems, leading to coral reef devastation and impacts on terrestrial systems that could negatively affect the breeding of endangered species. During a marine heatwave, warm sea surface temperatures influenced sand temperatures on sea turtle nesting beaches and resulted in unprecedented warm conditions on coral reefs. These conditions led to the most extreme female-biased hatchling sex ratio and lowest hatchling survival in nests in the last 70 years, with predicted increases in the frequency and intensity of marine heatwaves likely to have growing impacts on sea turtle nesting beaches and other terrestrial coastal environments.