In a 11-month field study, we deployed ex-situ reared Acropora millepora spat on coral seeding devices across 6 sites (3 from 'take' reserves open to fishing, 3 from 'no-take' reserves closed to fishing) in the Keppel Islands Great Barrier Reef Marine Park (Woppabura sea Country, inshore, southern Great Barrier Reef, Australia). Two devices with fish-exclusion features (exclusion star and exclusion triangle) were tested against a control device (featureless control star).
Mature gravid Acorpora millepora (Dana 1846) colonies were collected in November 2022 and transported back to the research vessel equiped with coral holding and spawning facilities. Gamete bundles were collected, separated, washed, fertilised, then transferred to larval rearing tanks where they remained until they reached settlement competency after 5-6 days. Conditioned concrete tabs (14 × 14 mm2; developed under the Reef Restoration and Adaptation Program) were used as settlement substrates. The tabs contained a mixed community of crustose coralline algae and bacteria biofilms that are known to induce settlement of Acorpora corals; these were conditioned in aquaria (National Sea Simulator, AIMS, Townsville) for 2-months prior to spawning and settlement.
Corals in devices were seeded to 6 sites, in one of the 13 experimental plots at ~4-6m depth (LAT). The hierarchical design included location (n=1), sites (n=6), experimental plots (n=13, 12 plots with 6 devices and 1 plot with 3), device type (n=3), contrete settlement tabs (n=3 for the exclusion star and control, n=6 for the exclusion triangle), and coral spat (n=~12 per tab) . Devices were semi-fixed in experimental plots (connected to reo bar via rope, with the reo hammered into the substrate) and hand placed by divers but had the potential to move within a given plot. Material was removed after 11 months.
Data were collected at 4 timepoints and included quantitative and qualitative assessments to determine the influence of biological (fish abundance and feeding, benthic composition) and environmental (sedimentation, reserve status, site) drivers on coral survival and size. Assessments were categorised and analysed by spatial scale: tab, plot, or site. Bayesian hierarchical logistic mixed-effects regression models, principal component and redundancy analyses were used to interogate the data. Please refer to the publication for more details on the statistical analyses.
