Twenty years of change in benthic communities across the Belizean Barrier Reef

Abstract

Disease, storms, ocean warming, and pollution have caused the mass mortality of reef-building corals across the Caribbean over the last four decades. Subsequently, stony corals have been replaced by macroalgae, bacterial mats, and invertebrates including soft corals and sponges, causing changes to the functioning of Caribbean reef ecosystems. Here we describe changes in the absolute cover of benthic reef taxa, including corals, gorgonians, sponges, and algae, at 15 fore-reef sites (12–15m depth) across the Belizean Barrier Reef (BBR) from 1997 to 2016. We also tested whether Marine Protected Areas (MPAs), in which fishing was prohibited but likely still occurred, mitigated these changes. Additionally, we determined whether ocean-temperature anomalies (measured via satellite) or local human impacts (estimated using the Human Influence Index, HII) were related to changes in benthic community structure. We observed a reduction in the cover of reef-building corals, including the long-lived, massive corals Orbicella spp. (from 13 to 2%), and an increase in fleshy and corticated macroalgae across most sites. These and other changes to the benthic communities were unaffected by local protection. The covers of hard-coral taxa, including Acropora spp., Montastraea cavernosa, Orbicella spp., and Porites spp., were negatively related to the frequency of ocean-temperature anomalies. Only gorgonian cover was related, negatively, to our metric of the magnitude of local impacts (HII). Our results suggest that benthic communities along the BBR have experienced disturbances that are beyond the capacity of the current management structure to mitigate. We recommend that managers devote greater resources and capacity to enforcing and expanding existing marine protected areas and to mitigating local stressors, and most importantly, that government, industry, and the public act immediately to reduce global carbon emissions.

Local anthropogenic stress does not exacerbate coral bleaching under global climate change

“…The distance of 50 km was selected after preliminary analyses showed negligible differences in model performance between 25, 50 and 100 km distance (Supporting Information Table S1). Therefore, the 50‐km distance was used as it represents a regularly used distance for studies investigating human impacts associated with coral reefs (Bruno & Valdivia, 2016; Moberg & Folke, 1999; Mora, 2008), and was found to consistently provide the best fit for models in studies where multiple other distances ranging from 10–500 km were used (Alves et al., 2022; Baumann et al., 2022). HPD represents a proxy of the implied impacts of local scale stressors (Bruno et al., 2019; Cinner et al., 2013; D’agata et al., 2014; Mora, 2008; Nyström et al., 2000; Williams et al., 2008) that have potential to exacerbate coral bleaching.…”

Institutional amnesia pushes fish spawning aggregations towards extirpation

“…Fully‐protected MPA sites in the Mesoamerican Reef have considerably higher grouper and snapper biomass than other MPA zoning categories (McField et al, 2022) which suggests that enforcement and compliance in those key areas are at least somewhat effective. Despite these results, both Alves et al (2022) and spawning site managers (Fulton et al, 2020) conclude that managers must continue to increase enforcement capacity. NGOs have been encouraging the governments of the four countries to increase enforcement for over 25 years.…”

“…Despite these results, both Alves et al (2022) and spawning site managers (Fulton et al, 2020) conclude that managers must continue to increase enforcement capacity. NGOs have been encouraging the governments of the four countries to increase enforcement for over 25 years.…”

Global change differentially modulates Caribbean coral physiology

“…Caribbean coral reefs have experienced considerable shifts in ecosystem composition since the 1970s defined by declines in several stony coral taxa [67,68], resulting in reefs now dominated by weedy and stress-tolerant species. Ocean acidification, warming, and the combination of…”

“…We are already witnessing species that were previously classified as stress-tolerant (i.e., P. strigosa) [45] shifting into a more susceptible category in the past several years alone [17,72], further highlighting the need to reassess how we label resilience in tropical reef-building corals. Similarly, Caribbean coral reef communities have experienced dramatic shifts in species composition and abundance over the past several decades [68]; therefore, many of the individuals within a species assessed today remain due to some level of resilience to stress. Overall, the susceptibility observed in this study across all species is indicative of future Caribbean coral reef assemblages composed only of the most tolerant individuals within a species, despite some species-level resilience to global change stressors.…”