Abstract
Coral reefs in the wider Caribbean declined in hard coral cover by ~80% since the 1970s, but spatiotemporal analyses for sub-regions are lacking. Here, we explored benthic change patterns in the Mexican Caribbean reefs through meta-analysis between 1978 and 2016 including 125 coral reef sites. Findings revealed that hard coral cover decreased from ~26% in the 1970s to 16% in 2016, whereas macroalgae cover increased to ~30% in 2016. Both groups showed high spatiotemporal variability. Hard coral cover declined in total 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. In 2016, more than 80% of studied reefs were dominated by macroalgae, while only 15% were dominated by hard corals. This stands in contrast to 1978 when all reef sites surveyed were dominated by hard corals. This study is among the first within the Caribbean region that reports local recovery in coral cover in the Caribbean, while other Caribbean reefs have failed to recover. Most Mexican Caribbean coral reefs are now no longer dominated by hard corals. In order to prevent further reef degradation, viable and reliable conservation alternatives are required.
Highlights
Monitoring change in coral reef ecosystems is essential in an era when humanity is having a widespread and long-term impact on nature
Our meta-analysis of ecological changes in the Mexican Caribbean showed that, on a regional scale, hard coral cover experienced a steady rate of decline between 1978 and 2004, mainly driven by hard coral cover loss in the Center and South regions, and a slow relative increase in the second period (2005–2016), mainly driven by Cozumel (Fig. 5A)
Macroalgae cover consistently increased across time and for most of the subregions in the Mexican Caribbean (MC) (Fig. 2B and 5B)
Summary
Monitoring change in coral reef ecosystems is essential in an era when humanity is having a widespread and long-term impact on nature. Current anthropogenic climate change and local stressors (such as overfishing and a mix of pollution and sedimentation from coastal development1) place coral reefs as the most endangered ecosystems on earth[2] Rapid reversals in their health have been reported globally[3], including reefs from the Caribbean region, where declines of the live hard coral cover of ~80% between 1975 and 2000 have been documented[4,5,6]. There are additional threats of the MC coral communities such as invading species (e.g. lionfish [Pterois volitans])[33] and the recent large floating mats of Atlantic Sargassum species reaching Western Caribbean coasts[34] The disintegration of these Sargassum mats releases nutrients and consumes oxygen, and decreases light availability at the seafloor, thereby affecting ecosystem functions such as benthic photosynthesis[35]. This study aims to answer the following questions: 1) What is the extent of hard coral and macroalgae (calcareous and fleshy) benthic cover change in the MC over the last 38 years? 2) Are there temporal and spatial patterns of change?
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