A meta-analysis to assess long-term spatiotemporal changes of benthic coral and macroalgae cover in the Mexican Caribbean

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. 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 development 1) 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 4-6. In the late 1970s, entire populations of reef-building coral species (i.e. Acropora palmata and Acropora cervicornis) collapsed as a result of the white-band disease 7. Furthermore, the mass mortality of black sea urchins (Diadema antillarum), overfishing and eutrophication 8 have resulted in a proliferation of more opportunistic, fast-growing organisms such as (macro)algae that outcompete reef-building corals 8-11. As a result, many Caribbean benthic coral reef communities changed drastically from low coral cover to persistent states of high cover (macro)algae in the process of so-called phase shifts 11-15. Efforts to mitigate or reverse phase shifts and reef degradation in the Caribbean include the development of new coral reef monitoring and managing strategies 16-18. Monitoring efforts of Caribbean reefs began in the late 1970s at various reef locations for short durations 19. It was until 1980 when coral reef monitoring programs first began for some countries due to the evident reef degradation and increasing threats 19. In the Mesoamerican Reef System (MAR), the monitoring officially began in 2005 with the Healthy Reefs for Healthy People Initiative 20. The MAR is recognized by the World Wildlife Fund (WWF) as one of 200 global priority ec...

Recovery disparity between coral cover and the physical functionality of reefs with impaired coral assemblages

“…and Orbicella spp., which highlights the need to be cautious when considering the contribution of increases in coral cover to the long‐term physical functionality of Caribbean coral reefs. Overall, the increase in coral cover we report here (from 9.15 ± 0.57% to 14.84 ± 0.92%) is far from the historical values of this region (>30%; Contreras‐Silva et al., 2020). This, in conjunction with the unsuccessful recovery of reef framework corals and the rapidly increasing dominance of non‐framework species across the region, might explain the lack of functional recuperation of the coral reefs in the Mexican Caribbean.…”

“…Despite widespread paucity at a regional level, there are a few examples of Caribbean reefs that have shown evidence of recovery, with some reefs returning to predisturbance levels of coral cover. The recovery of these reefs has been largely found to be driven by effective and sustainable management, healthy herbivore populations, low hurricane frequency, and limited terrestrial runoff (Contreras‐Silva et al., 2020; Idjadi et al., 2006; Steneck et al., 2019).…”

Two decades of carbonate budget change on shifted coral reef assemblages: are these reefs being locked into low net budget states?

“…A series of acute and chronic disturbances led to these major declines in coral cover and associated increases in the coverage of macroalgae and the loss of structural complexity between the late 1970s and early 2000s [36]. Although coral cover has shown some signs of recovery since [36], there are no clear signs that the capacity of the coral communities to increase calcium carbonate accumulation rates have changed, at least at equivalent rates [26,36]. This has been largely owing to a lack of recovery by the most important functional groups in the coral community.…”

Massive Influx of Pelagic Sargassum spp. on the Coasts of the Mexican Caribbean 2014–2020: Challenges and Opportunities

“…In the last 40 years, the coral cover along this coast has decreased significantly. This is due to combined local and global anthropogenic impacts: coastal development and associated pollution, rising sea temperatures, which have increased coral diseases and bleaching episodes, and the occurrence of hurricanes [28][29][30]. In the northern section, for example, coral cover has declined by 50% since the late 1970s, mainly due to significant loss of important, framework-building, coral taxa [31].…”