Relative roles of biological and physical processes influencing coral recruitment during the lag phase of reef community recovery

Abstract

Following disturbances, corals recolonize space through the process of recruitment consisting of the three phases of propagule supply, settlement, and post-settlement survival. Yet, each phase is influenced by biophysical factors, leading to recruitment success variability through space. To resolve the relative contributions of biophysical factors on coral recruitment, the recovery of a 150 km long coral reefs in Palau was investigated after severe typhoon disturbances. Overall, we found that benthic organisms had a relatively weak interactive influence on larval settlement rates at the scale of individual tiles, with negative effects mainly exerted from high wave exposure for Acropora corals. In contrast, juvenile coral densities were well predicted by biophysical drivers, through both direct and indirect pathways. High densities of Acropora and Poritidae juveniles were directly explained by the availability of substrata free from space competitors. Juvenile Montipora were found in higher densities where coralline algae coverage was high, which occurred at reefs with high wave exposure, while high densities of juvenile Pocilloporidae occurred on structurally complex reefs with high biomass of bioeroder fish. Our findings demonstrate that strengths of biophysical interactions were taxon-specific and had cascading effects on coral recruitment, which need consideration for predicting reef recovery and conservation strategies.normality of model residuals. Explanatory variables were scaled during the analytic procedure in the function sem.coefs 84 . Benthic variables are naturally collinear, and were only added to models when suggested as missing links and if the variation inflation factor remained low (<5). The goodness of fit of SEMs were assessed using a directional separation test (d-separations test) Fisher's C statistic 84 . Once relationships were detected within the SEM framework, details on the shapes of the relationships among variables were explored using ABT 80 .Univariate and SEM analyses were conducted using R version 3.5.2 85 using lme4 86 , lsmeans 87 , abt 80 , and piecewiseSEM 84 packages. Multivariate analyses were conducted using PRIMER-E v.6 with PERMANOVA extension 88,89

Settlement of larvae from four families of corals in response to a crustose coralline alga and its biochemical morphogens

“…The lack of settlement by Montipora aequituberculata in response to live CCA was surprising given that this species is within the family Acroporidae and because Montipora spp. can be found in environments amongst CCA such as P. onkodes 35,36 . Yet, M. aequituberculata is not dominant on the reef crest where P. onkodes thrives 35 , whereas many of the Acropora species tested are common in that environment.…”

Spatiotemporal variation in coral recruitment and its association with seawater temperature

“…Herbivorous fish modify the distribution of coral recruits as a function of wave exposure, with herbivory promoting coral recruitment in crevices through increased abundance of crustose coralline algae under calm seawater conditions (Doropoulos et al 2016 b ). Wave exposure modifies the flora and fauna on settlement tiles, thereby affecting coral recruitment, with greater exposure increasing the density of Acropora recruits (Gouezo et al 2020). These Palauan studies did not include a test for association between temperature and recruitment, however, perhaps because their emphasis on space (i.e., over 150 km of reef) rather than time (15–24 months) precluded sampling across different thermal regimes.…”

“…Such effects are likely to be valuable in understanding the differences in coral recruitment between the Indo-Pacific and the tropical western Atlantic (Smith 1992;Glassom et al 2004;Price et al 2019), and why such effects are not evident in the present contrast of Mo'orea and St. John. While the response of coral larvae to abiotic conditions are relatively well known, especially for temperature (Gleason and Hofmann 2011;Graham et al 2017), quantitative analyses of the factors causing coral recruitment to vary are only beginning to emerge (Gouezo et al 2020). The role of stockrecruitment relationships in determining rates of coral recruitment has been considered for decades (Caley et al 1996), but the probability that these relationships will be strong depends on the extent to which coral populations are self-seeding (i.e., their larvae disperse short distances; Sammarco and Andrews 1988), vs. open and exposed to larvae from distant sources (e.g., Serrano et al 2016).…”

Corallivory varies with water depth to influence the growth of Acropora hyacinthus, a reef‐forming coral

“…2019, Gouezo et al. 2020). Among physical factors, water depth appears to be important (Sheppard and Obura 2005, Adjeroud et al.…”

“…Coral reefs are dynamic ecosystems that have evolved and persisted through catastrophic disturbances, such as hurricanes (Knowlton et al 1990, Gardner et al 2005, predator outbreaks (Cox 1986, De'ath et al 2012, Kayal et al 2012, and increasingly frequent coral bleaching events (Hoegh-Guldberg 1999, Eakin et al 2010, Sully et al 2019), all of which can cause the mass mortality of corals. When a coral community is disturbed and corals die, the speed and trajectory of recovery is influenced by a myriad of physical and biological factors (Connell 1978, Steneck et al 2019, Gouezo et al 2020). Among physical factors, water depth appears to be important (Sheppard andObura 2005, Adjeroud et al 2018) because multiple abiotic factors change rapidly with depth (Spencer Davies 1989, Pratchett et al 2015.…”