Half of coral species that occur on Caribbean reefs have also been reported living in mangroves. Given the vulnerability of corals living on reefs to environmental change, populations of the same species living in mangroves may prove critical to longterm survival of these coral species and the resilience of nearby reefs. To date, few studies have addressed the health and viability of mangrove coral populations, which is necessary if we are to understand their role in the broader meta-community.Here we present the first longitudinal study of the distribution, survival, growth, and recruitment of a mangrove coral population over multiple years. From 2014 to 2018, we fully censused a population of Porites divaricata along 640 meters of a mangrovelined channel at Calabash Caye, Belize, and beginning in 2015, we tagged individual colonies for longitudinal monitoring. Year-to-year survivorship averaged 66.6% (±3.9 SE), and of the surviving colonies, on average, 72.7% (±2.5 SE) experienced net growth. The number of colonies, their spatial distribution, and population size-structure were essentially unchanged, except for an unusually high loss of larger colonies from 2016 to 2017, possibly the result of a local disturbance. However, each annual census revealed substantial turnover. For example, from 2016 to 2017, the loss or death of 72 colonies was offset by the addition of 89 recruits. Integral projection models (IPM) for two consecutive one-year intervals implicated recruitment and the persistence of large colonies as having the largest impacts on population growth. This 5-year study suggests that the P. divaricata population in the mangroves is viable, but may be routinely impacted by disturbances that cause the mortality of larger colonies. As many corals occur across a mosaic of habitat types, understanding the population dynamics and life-history variability of corals across habitats, and quantifying genetic exchange between habitats, will be critical to forecasting the fate of individual coral species and to maximizing the efficacy of coral restoration efforts.

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.

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

No abstract

Corals are critical to marine biodiversity. Reproduction and dispersal are key to their resilience, but rarely quantified in nature. Exploiting a unique system—a fully censused, longitudinally characterized, semi-isolated population inhabiting mangroves—we used 2bRAD sequencing to demonstrate that rampant asexual reproduction most likely via parthenogenesis and limited dispersal enable the persistence of a natural population of thin-finger coral ( Porites divaricata ). Unlike previous studies on coral dispersal, knowledge of colony age and location enabled us to identify plausible parent–offspring relationships within multiple clonal lineages and develop tightly constrained estimates of larval dispersal; the best-fitting model indicates dispersal is largely limited to a few metres from parent colonies. Our results explain why this species is adept at colonizing mangroves but suggest limited genetic diversity in mangrove populations and limited connectivity between mangroves and nearby reefs. As P. divaricata is gonochoristic, and parthenogenesis would be restricted to females (whereas fragmentation, which is presumably common in reef and seagrass habitats, is not), mangrove populations likely exhibit skewed sex ratios. These findings suggest that coral reproductive diversity can lead to distinctly different demographic outcomes in different habitats. Thus, coral conservation will require the protection of the entire coral habitat mosaic, and not just reefs.