Quantifying exceptionally large populations of <I>Acropora</I> spp. corals off Belize using sub-meter satellite imagery classification

Abstract

Caribbean coral reefs have experienced dramatic declines in live coral cover in recent decades. Primary branching framework Caribbean corals, Acropora cervicornis (Lamarck, 1816) and Acropora palmata (Lamarck, 1816), have suffered the greatest collapse. Coral Gardens, Belize, is one of few remaining, and perhaps the largest, refugia for abundant, healthy, but undocumented populations of both Acropora species in the Caribbean Sea. In the present study, GeoEye-1 multispectral satellite imagery of a 25 km 2 reefal area near Ambergris Caye, Belize, was analyzed to identify live Acropora spp. cover. We used a supervised classification to predict occurrence of areas with live Acropora spp. and to separate them from other benthic cover types, such as sandy bottom, seagrass, and mixed massive coral species. We tested classification accuracy in the field, and new Acropora spp. patches were mapped using differential GPS. Of 11 predicted new areas of Acropora spp., eight were composed of healthy Acropora spp. An unsupervised classification of a red (Band 3):blue (Band 1) ratio calculation of the image successfully separated Acropora corals from other benthic cover, with an overall accuracy of 90%. Our study identified 7.58 ha of reef dominated by Acropora spp. at Coral Gardens, which is one of the largest populations in the Caribbean Sea. We suggest that Coral Gardens may be an important site for the study of modern Acropora spp. resilience. Our technique can be used as an efficient tool for genera-specific identification, monitoring, and conservation of populations of endangered Acropora spp. Caribbean coral reefs have experienced significant decline in live coral cover in recent decades (

Age and intraspecific diversity of resilient Acropora communities in Belize

“…Peckol et al (2003) and Brown-Saracino et al (2007) reported live coral cover (all species) in this area exceeding 43%. More recently, Busch et al (2016) reported an average value of * 30% live A. cervicornis coral cover (species specific) in the Acropora thickets sampled in this study. The extent of live Acropora thickets in the greater Coral Gardens area exceeded 7.5 ha in 2015, making it one of the largest documented sites of its kind in the Caribbean (Busch et al 2016).…”

“…However, because Caribbean acroporids usually do not self-fertilize, production of sexual offspring is a function of the number of genotypes present and not just a function of colony density or size (Levitan and McGovern 2005;Fogarty et al 2012;Baums et al 2013;Williams et al 2014). Our study suggests that while Coral Gardens may be the largest extant acroporid site in the Caribbean (Busch et al 2016), this may not translate into successful downstream sexual recruitment. Only observation of spawning and gamete-crossing experiments at these sites would provide additional insight into the production of gametes by these stands.…”

“…Despite Caribbean-wide declines, relatively abundant A. cervicornis and A. palmata populations have been reported in Honduras (Keck et al 2005;Purkis et al 2006), the Dominican Republic , Mexico (Larson et al 2014), Florida (Fort Lauderdale area; Vargas-Angel et al 2003), and Belize (Peckol et al 2003;Brown-Saracino et al 2007;Macintyre and Toscano 2007;Busch et al 2016). These studies have variably included general habitat surveys, quantification of percentage of algal and live coral coverage, Acropora colony sizes, number of Acropora colonies, fish and invertebrate population densities, imagebased spatial characterization, and disease prevalence, but none included genetic data.…”

Identifying Causes of Temporal Changes in Acropora cervicornis Populations and the Potential for Recovery

“…This dramatic decline leads to its listing as threatened under the United States Endangered Species Act (US ESA;National Marine Fisheries Service, 2006) and as critically endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (Aronson et al, 2008). Since this dramatic decline, recovery has been limited with few known high cover populations remaining throughout the species' range (Vargas-Ángel et al, 2003;Keck et al, 2005;Grober-Dunsmore et al, 2006;Lirman et al, 2010;Walker et al, 2012;Busch et al, 2016). One region where numerous large patches of A. cervicornis exist today is within the Southeast Florida Coral Reef Ecosystem Conservation Area and more specifically in Broward County, FL, at the northern-most extent of this species' range (Vargas-Ángel et al, 2003;Walker et al, 2012;D'Antonio et al, 2016).…”

Coral Gardens Reef, Belize: A refugium in the face of Caribbean-wide Acropora spp. coral decline

“…However, an increasingly robust literature on nurseries, reintroduction, conservation, and even assisted evolution of corals is emerging [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]. As the field expands from understanding why corals die to how we can promote restoration of these important ecological niches in a changing world, studies increasingly look to successful reefs to understand robustness, resilience, and temporal persistence [10,33,49,[53][54][55][56][57][58][59][60][61][62][63][64][65][66][67]]. If we can identify the 'reefs that work' in spite of recent anthropogenic and environmental change we may be able to better characterize their features and facilitate reef expansion, cultivate nurseries, re-seed reefs, and conserve a dwindling ecological resource [63,68,69]; providing hope for the future of Caribbean coral reefs [70] and possibly beyond.…”