Corals of the genus Porites are a locally abundant component of the epibiont community on mangrove prop roots at Calabash Caye, Turneffe Atoll, Belize

Abstract

Mangrove prop roots support diverse epibiont communities, but they are generally regarded as inhospitable for corals. However, recent reports have documented corals thriving on mangrove roots in the U.S. Virgin Islands and Cuba, and it has been proposed that mangroves may provide a refuge from environmental conditions that trigger coral mortality on nearby reefs. It also raises interesting questions about the potential evolutionary significance of coral populations in mangrove forest. We investigated diverse mangrove habitats for the presence of corals at Calabash Caye, Belize, part of a recently designated marine reserve on Turneffe Atoll. Here we present data on the distribution, size and morphology of 127 colonies of branching Porites found in a survey of 1858 meters of mangrove prop roots fringing three qualitatively distinct bodies of water: a high-flow channel, a moderate-flow creek, and a low-flow mangrove pond. The distribution of Porites was highly clumped, with 108 colonies occurring in a 178-meter stretch of shoreline along the high flow channel. Colony morphology varied widely, from bushy colonies with more than 40 branch tips per 1000 cm3 of ecological volume, to spindly colonies with fewer than 10 branch tips per 1000 cm3, to new recruits that have not yet developed distinct branches. Comparisons of the same coral-bearing roots in 2013 and 2014 revealed that colonies can experience substantial growth in a year’s time. We also document a much more diverse coral fauna living in the mangroves at Crooked Creek, a high flow environment on the western edge of Turneffe Atoll. The data described here contribute to an emerging picture of mangroves as potentially important habitat for corals, while suggesting that different types of mangrove habitat vary in their suitability for different species of coral. Future studies are needed to identify the critical environmental features of mangrove habitats that support coral, to further characterize those corals that can utilize mangrove habitat, and to investigate potential connectivity between coral populations in mangroves and nearby reef habitats.

Phenotypic variation in two widespread Caribbean corals —Porites astreoidesandP. divaricata— between mangrove and lagoon habitats

“…Length and width were measured in a plane parallel to the substratum, with length representing the greatest linear dimension parallel to the substrate, and width measured at a point rotated 90° from where the length was taken. For corals growing on mangrove roots, linear dimensions were measured as previously described (Bengtsson et al 2019, Scavo Lord et al 2020. Height was measured as the perpendicular distance from the root to the most distant extent of the colony.…”

“…However, reefs are not the only habitat in which corals can live. Many coral species are habitat generalists that can thrive in a multitude of different environments in addition to coral reefs, including mangrove forests (Yates et al 2014, Hernández Fernández 2015, Rogers 2017, Bengtsson et al 2019, Camp et al 2019) and seagrass beds (Camp et al 2016, Lohr et al 2017. For example, around half of the approximately 75 coral species that occur on Caribbean reefs also occur in mangrove habitats (Scavo Lord et al 2020).…”

“…These two weedy corals can be found in a wide variety of habitats. The thin finger coral, P. divaricata, is common in shallow lee habitats, including the reef crest, seagrass beds, mangrove forests and lagoonal patch reefs (Veron 2000, Hernández Fernández 2015, Camp et al 2016, Rogers 2017, Bengtsson et al 2019. This branching coral can vary greatly in overall shape, number and density of branch tips, and color ( Figure 2).…”

“…This branching coral can vary greatly in overall shape, number and density of branch tips, and color ( Figure 2). The mustard hill coral, P. astreoides, can be found in all reef habitats at depths between 0-50 m, as well as mangrove forests, seagrass beds, and shallow lagoon patch reefs (Veron 2000, Hernández Fernández 2015, Camp et al 2016, Rogers 2017, Bengtsson et al 2019. This species has highly variable morphology and color ( Figure 3), existing as a massive, encrusting, or plating form, with a smooth or bumpy surface, and colors ranging from bright yellow to medium gray to dark brown (Veron 2000).…”

“…While previous studies have explored the phenotypic variation of P. astreoides (Gleason 1993) and P. divaricata (Bengtsson et al 2019) within habitat types, this study characterized differences between coral species inhabiting mangrove and lagoon habitats. Given that mangrove and lagoon habitats differ in key environmental parameters including temperature and light, we hypothesized that colonies from the two study locations would exhibit consistent and predictable differences in phenotype.…”