Epibiont community composition of red mangroves Rhizophora mangle are contingent on root characteristics

Authors: STEWART, HEATHER - McGill University - Canada; JANIAK, DEAN - Smithsonian Marine Station; WRIGHT, JENNIFER - University Of Miami; HUNT, DAVID A. G. A. - McGill University - Canada; Carmona, Andrea; POWELL, KRYSTYNA - Florida Atlantic University; CHAPMAN, LAUREN - McGill University - Canada; ALTIERI, ANDREW - Smithsonian Tropical Research

Submitted to: Marine Ecology Progress Series
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2021
Publication Date: 3/24/2022
Citation: Stewart, H.A., Janiak, D.S., Wright, J.L., Hunt, D., Carmona Cortes, A., Powell, K.T., Chapman, L.J., Altieri, A.H. 2022. Epibiont community composition of red mangroves Rhizophora mangle are contingent on root characteristics. Marine Ecology Progress Series. 686:15–35. https://doi.org/10.3354/meps13999.
DOI: https://doi.org/10.3354/meps13999

Interpretive Summary: Mangroves are an important architectural species, specifically along coastal regions. The prop roots of the red mangrove tree (Rhizophora mangle) are considered primary architectural species. These roots form complex habitats, which allow communities of different species to thrive. Some of those communities are composed of epibionts, or sessile organisms. This kind of interactions between the roots and the organisms on the roots are a great way to study species associations. To test these associations we used living, and non-living prop roots, PVC, and wood. Mobile invertebrate organisms were also quantified. We found that the type of composition, i.e., substrate is important in defining both the epibiont community and the invertebrate community. These results show that mangrove habitat serve a critical role in maintaining complex communities and help inform restoration efforts.

Technical Abstract: Foundation species traits that structure communities are rarely experimentally examined; thus, a predictive understanding of their functions lags behind patterns of observed species associations. Red mangrove Rhizophora mangle roots form complex living habitats that support diverse epibiont communities, making them a model system for testing links between variation in foundation species traits and associated biodiversity. Here, we compared epibiont community composition between living and non-living mangrove roots, as well as root mimics, to test how foundation species traits affect community structure. We also quantified the community structure of associated mobile invertebrates to examine their relationship with secondary foundation species (e.g. sponges, bivalves) that grow on the roots. After 14 mo of colonization and succession, substrate composition (i.e. mangrove, wood, PVC) had significant effects on community composition, richness, and abundance of sessile epibionts and mobile invertebrates. Non-living mangrove roots were 5 times more likely to deteriorate, and consequently had the lowest epibiont richness and abundance. We found strong positive relationships between mobile invertebrate richness and the abundance, measured as biomass, and richness of sponges and bivalves, suggesting that variation among roots in secondary foundation species play an important role in mediating mobile invertebrate community composition. This study highlights the functional role of habitat structure and how rapidly that function can be lost without biogenic maintenance. Our results indicate the importance of facilitation cascades in fostering diverse mobile invertebrate communities and highlight both advantages and limitations in using artificial structures in restoration programs.