Community change within a Caribbean coral reef Marine Protected Area following two decades of local management

© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS ONE 8 (2013): e54069, doi:10.1371/journal.pone.0054069.Structural change in both the habitat and reef-associated fish assemblages within spatially managed coral reefs can provide key insights into the benefits and limitations of Marine Protected Areas (MPAs). While MPA zoning effects on particular target species are well reported, we are yet to fully resolve the various affects of spatial management on the structure of coral reef communities over decadal time scales. Here, we document mixed affects of MPA zoning on fish density, biomass and species richness over the 21 years since establishment of the Saba Marine Park (SMP). Although we found significantly greater biomass and species richness of reef-associated fishes within shallow habitats (5 meters depth) closed to fishing, this did not hold for deeper (15 m) habitats, and there was a widespread decline (38% decrease) in live hard coral cover and a 68% loss of carnivorous reef fishes across all zones of the SMP from the 1990s to 2008. Given the importance of live coral for the maintenance and replenishment of reef fishes, and the likely role of chronic disturbance in driving coral decline across the region, we explore how local spatial management can help protect coral reef ecosystems within the context of large-scale environmental pressures and disturbances outside the purview of local MPA management.Funding was provided by the Saba Conservation Foundation ((SCF), King Abdullah University of Science and Technology, The Australian National University and Australian Research Council

Effects of coral bleaching and coral loss on the structure and function of reef fish assemblages

Mass coral bleaching, caused by elevated ocean temperatures, has now emerged as a major, if not the single most important, contributor to elevated rates of coral mortality (Hughes et al. 2017; Chaps. 3, 4, and 13), greatly accelerating the degradation of coral reef ecosystems throughout the world. Coral reefs have been subject to increasing anthropogenic disturbances and threats throughout the last few decades (if not centuries), resulting in sustained declines in the cover or abundance of scleractinian corals and corresponding shifts in the structure of reef habitats (Hughes et al. 2003; Alvarez-Filip et al. 2011). Climate change (specifically resulting in coral bleaching) is almost always considered, along with a variety of other more localised anthropogenic disturbances and threats, as a key contributor to sustained and ongoing coral loss (e.g. De'ath et al. 2012). However, mass coral bleaching has previously been considered to be a relatively minor, though emerging and increasingly important, contributor to coral loss, especially relative to other major disturbances such as severe tropical storms and outbreaks of coral predators (Pratchett et al. 2011a; De'ath et al. 2012). The extent and severity of the latest (2014–2017) global bleaching event (Hughes et al. 2017, 2018), as well as successive years of severe bleaching in many locations, have firmly heralded in an era where global climate change is the foremost threat to coral reef ecosystems

Biodiversity of Reef-Building, Scleractinian Corals

Zooxanthellate scleractinian corals are moderately well-known for shallow reef habitats, but not for mesophotic depths (>30 m) that are relatively difficult to access. Mesophotic habitats are light-limited, with different hydrodynamics and sedimentation processes, which result in growth forms that are often difficult to classify using traditional schemes based largely on shallow reef specimens. We analyzed published data and museum records, using specimen-based records to minimize classification issues, finding 53 mesophotic species in the western Atlantic Ocean (85% of total species) and 338 in the Indo-Pacific (45%). Only four species were recorded exclusively below 30 m depth, while the great majority were common shallow reef taxa. Over 96% of western Atlantic and 82% of Indo-Pacific genera and most coral lineages were represented below 30 m depth. In the Indo-Pacific, species and genus richness varied widely between regions and were significantly correlated with shallow reef species richness. Overall, species richness decreased steadily with increasing depth, with little evidence for distinct faunal boundaries: 157 species occurred >= 60 m and 31 deeper than 100 m, with species occurrence only moderately related to phylogeny. Our knowledge of mesophotic biodiversity is rapidly changing as more regions are documented and new molecular techniques suggest taxonomic revisions and resolve deepwater cryptic species. We conclude that mesophotic scleractinian fauna are largely a subset of shallow scleractinian fauna, comprising a significant proportion of coral species and most genera, with the potential to play a significant role in lineage preservation and the future of coral reefs