The Mexican Caribbean Reefs: from benthic changes and stressors towards a sustainable management strategy

Abstract

The Mexican Caribbean is home to many coral reefs with a high ecological and economic value for people in the country and beyond. Nevertheless, these ecosystems are highly threatened due to a combination of global (anthropogenic climate change) and local stressors (mass tourism, land-based pollution, and overuse of resources). The decline of the wider Caribbean coral reefs has been alarming, with an average loss of 40 percent of absolute coral cover since the late 1970s. However, the current literature lacks spatiotemporal information on the coral and macroalgae cover development and longitudinal studios regarding the stressors causing changes in Mexican Caribbean reefs. Therefore, this thesis aimed first to understand the benthic dynamics of change and the main stressors causing these changes to finally propose a conceptual framework to improve coral reef management. A large-scale spatiotemporal analysis between 1978 and 2016 on coral and macroalgae cover in the Mexican Caribbean reefs was conducted through meta-analysis. Here, findings revealed that hard coral cover decreased from ~ 26 % in the 1970s to 16 % in 2016, whereas macroalgae cover increased from ~ 16 % in the 1980s to ~ 30 % in 2016. Both groups showed high spatiotemporal variability. Hard coral cover declined by 12 % from 1978 to 2004 but increased again by 5 % between 2005 and 2016, indicating some coral recovery after the 2005 mass bleaching event and hurricane impacts. Additionally, a cumulative impact assessment on hard coral and macroalgae benthic communities exposed to multiple stressors (thermal stress, nutrient inflow, sedimentation, hurricane impact, and anthropisation) was conducted using an extensive remote sensing data collection. These data were coupled with 91 coral reef monitoring sites from 2005 to 2016, and the estimates of the change in coral and macroalgae cover percentage were related to each factor considered a potential stressor impacting reefs. Results showed that sea surface temperature increased by 0.30 °C in 12 years, and bleaching susceptibility strongly influenced coral cover change, followed by the negative effect of anthropogenic activities, which incorporates the increasing pressures of urban hubs. The water quality predictors, primarily the particulate organic carbon (used as a proxy for sedimentation and nutrients), only affected macroalgae cover. The only adverse effect on macroalgae was sea surface temperature and chlorophyll-a interaction. Analyses here revealed that global warming impacts on coral reefs occur parallel with local pressures, such as increases in nutrients and suspended sediments through coastal development. The future of Mexican Caribbean coral reefs is at high risk due to cumulative impacts from local and global stressors despite monitoring and restoration efforts over the past few decades, which begs the question of why and how protection and management may be improved. Consequently, a conceptual framework was generated focusing on an integrated management strategy to improve the understanding of the unique and vital services that coral reef ecosystems in the Mexican Caribbean provide. Within this spectrum, a Cybercartographic atlas was proposed because it offers an excellent method for creating a conceptual framework for such a management tool. The ultimate objective is to make arguments accessible that serve as a baseline for assisting and setting priorities for governance in political decisions.