Impacto das ondas de calor marinhas em ecossistema recifal no litoral do Ceará (NE, Brasil)

Abstract

The coral reef is the ecosystem most threatened by rising sea temperatures, in addition to being susceptible to climate change. Ocean warming and strong sunlight exposure are stressors for coral communities leading to thermal stress, causing the expulsion of zooxanthellae and ultimately bleaching. Several seasonal conditions locally affect bleaching, such as temperature and turbidity, so they are relevant factors during thermal stress. Thus, reefs under stressful conditions have less recovery capacity. Furthermore, the combination of these factors with extreme weather events such as Marine Heat Waves (MHWs) reduces the ability of coral reefs to recover from disturbances. Extreme ocean temperature events above the 90th percentile lasting 5 or more days are termed marine heat waves (MHWs). Thus, monitoring its situation on a regional scale becomes relevant and remote sensing provides an effective tool in identifying these events. However, in the Equatorial Atlantic, there are few studies on its relationship with bleaching. The oceanographic conditions from 2002 to 2022 were investigated and based on this, four points were selected to determine the frequency, duration and intensity of MHWs in two coastal reefs and two offshore reefs. The MHWs that occurred in the studied area had their properties accentuated since 2010. The maximum intensity tends to occur in the summer and autumn in the study area. The focus of the work was mainly on three periods, which are the summer/autumn of 2020, the winter/spring of 2021 and autumn of 2010, periods of MHWs and consequent coral bleaching. The most intense MHWs occurred in the coastal reef of area B and the highest cumulative intensity was in the offshore region of area C. It is estimated that turbidity in the coastal reef of area B, combined with other stressors, may have influenced the bleaching in the reported period. On offshore reefs, high temperature and turbidity may have caused bleaching in the reporting period. Given the above, this study aimed to determine MHWs events and relate them to environmental variables to correlate with coral bleaching events reported in the literature.