Identifying mangrove-coral habitats in the Florida Keys

Abstract

Coral reefs are degrading due to many synergistic stressors. Recently there have been a number of global reports of corals occupying mangrove habitats that provide a supportive environment or refugium for corals, sheltering them by reducing stressors such as oxidative light stress and low pH. This study used satellite imagery and manual ground-truthing surveys to search for mangrove-coral habitats in the Florida Keys National Marine Sanctuary and then collected basic environmental parameters (temperature, salinity, dissolved oxygen, pHNBS, turbidity) at identified sites using a multi-parameter water quality sonde. Two kinds of mangrove-coral habitats were found in both the Upper and Lower Florida Keys: (1) prop-root corals, where coral colonies were growing directly on (and around) mangrove prop roots, and (2) channel corals, where coral colonies were growing in mangrove channels under the shade of the mangrove canopy, at deeper depths and not in as close proximity to the mangroves. Coral species found growing on and directly adjacent to prop roots included Porites porites (multiple morphs, including P. divaricata and P. furcata), Siderastrea radians, and Favia fragum. Channel coral habitats predominantly hosted S. radians and a few S. siderea, although single colonies of Solenastrea bournoni and Stephanocoenia intersepta were observed. Although clear, low-turbidity water was a consistent feature of these mangrove-coral habitats, the specific combination of environmental factors that determine which mangrove habitats are favorable for coral recruitment remains to be defined. Circumstantial evidence suggests additional coral communities existed on mangrove shorelines of oceanside and backcountry islands until destroyed, likely by Hurricane Irma. These mangrove-coral habitats may be climate refugia for corals and could be included in ecosystem management plans and considered for their applications in coral restoration.

Distinct Phenotypes Associated with Mangrove and Lagoon Habitats in Two Widespread Caribbean Corals, Porites astreoides and Porites divaricata

“…Mangroves are increasingly being recognized as an important component of the ecological niche for many coral species (Yates et al, 2014;Hernández Fernández, 2015;Rogers, 2017;Bengtsson et al, 2019;Camp et al, 2019;Kellogg et al, 2020;Scavo Lord et al, 2020). Here, we demonstrate significant differences in key environmental variables between the mangrove and adjacent coral-supporting habitats.…”

“…To our knowledge, this is the first study to directly compare the phenotype of corals inhabiting mangrove prop root and shallow lagoonal patch reef habitats. Given increasing interest in the role of non-reef habitats for supporting coral resilience (Yates et al, 2014;Hernández Fernández, 2015;Rogers, 2017;Bengtsson et al, 2019;Camp et al, 2019;Kellogg et al, 2020;Scavo Lord et al, 2020), it is important to understand whether and how coral phenotypes can change to accommodate the conditions found in what have historically been regarded as suboptimal habitats for corals, such as mangroves. The data presented here document intraspecific phenotypic differences in 000 two species between one lagoon site and two mangrove sites on Turneffe Atoll.…”

“…Many coral species are habitat generalists that can thrive in a multitude of different environments in addition to coral reefs, including seagrass beds (Camp et al, 2016;Lohr et al, 2017) and mangroves. With respect to mangroves, corals have been reported growing directly on mangrove prop roots (Rogers and Herlan, 2012;Yates et al, 2014;Hernández Fernández, 2015;Rogers, 2017;Bengtsson et al, 2019;Kellogg et al, 2020), on the benthos under the shade of the mangrove canopy (Rogers and Herlan, 2012;Yates et al, 2014;Rogers, 2017;Kellogg et al, 2020), and in lagoonal habits bounded by mangroves, although not shaded by the mangrove canopy (Rogers and Herlan, 2012;Yates et al, 2014;Camp et al, 2016Camp et al, , 2019Rogers, 2017). About half of the approximately 75 coral species that occur on Caribbean reefs also occur in mangrove habitats (Rogers and Herlan, 2012;Yates et al, 2014;Hernández Fernández, 2015;Rogers, 2017;Bengtsson et al, 2019;Kellogg et al, 2020).…”

Neither Coral- nor Symbiont- Genetic Diversity may Explain the Resistance of the Coral <i>Echinopora lamellosa</i> to Bleaching

“…Mangrove vegetation not only exports litter to its adjacent ecosystems but also disperse dissolved tannin (López-Portillo et al 2017;Stewart et al 2021). The dissolved tannin and other chromophoric dissolved organic matter (CDOM) derived from marine plants may protect corals under the stress of water temperature from excessive ultraviolet radiation (UV-R) exposure and act as a pH buffer during the bleaching (Kellogg et al 2020). Such a mechanism may provide coral refugia that increase coral survival from bleaching.…”

Caribbean mangrove forests act as coral refugia by reducing light stress and increasing coral richness

“…Red mangroves ( Rhizophora mangle ) frequently occur in close proximity to reefs, and there are a few studies documenting the occurrence of corals growing among and near the mangrove roots such as in the saltwater ponds and channels of Belize (Macintyre et al 2000, Rutzler et al 2000, Bengtsson et al 2019, Scavo Lord et al 2020), bays of the U.S. Virgin Islands (Rogers 2009, Rogers and Herlan 2012, Yates et al 2014), and the Florida Keys (Kellogg et al 2020). These observational studies suggest that mangroves can serve as an alternative habitat for corals and perhaps a refugium in the face of continued reef degradation.…”