High incidence of partial colony mortality constrains realized growth for three coral species (Montastraea cavernosa, Porites astreoides and Siderastrea siderea) in southeast Florida

Growth rates of individual coral colonies are a key demographic trait which can reveal fundamental changes in population health and resilience. With changing environmental conditions on coral reefs assessing spatial, temporal and taxonomic variation in net coral growth (accounting for growth and partial mortality) is fundamental to understanding the changing structure and dynamics of coral populations and communities. In recent years, the Southeast Florida Coral Reef Ecosystem Conservation Area has experienced mass coral mortality from heat stress and disease, which has seen increased focus placed on restoration. Yet it is unclear whether there is chronic growth suppression which reduces recovery potential and whether growth rates vary within and between species spatially. We quantified interannual changes in Montastraea cavernosa, Porites astreoides, and Siderastrea siderea growth rate and linear extension between 2000 and 2020 to specifically test intraspecific, interspecific and spatiotemporal variations in growth rate and partial mortality. Of the 136 tracked colonies, 33% died and 89% had partial mortality. Small M. cavernosa and P. astreoides colonies generally grew faster than large colonies and had less partial mortality, but S. siderea consistently had high partial mortality. M. cavernosa and S. siderea growth primarily declined following acute disturbance, but growth rates in all species were often low during inter-disturbance periods. Maximum growth rates of each species align with those found elsewhere in the Caribbean, but partial mortality prevalence and extent was exceptionally high, particularly in large colonies, which suppressed realized growth. As a result, colonies of each species reached just a third of their potential size after 20 years, contributing to low resilience which hampers recovery capacity.