Site mediates performance in a coral‐seeding trial

Abstract

Coral seeding is a promising intervention being tested and applied in global reef‐restoration efforts. However, high mortality of newly settled corals, particularly in degraded environments, is one of several hurdles to overcome to up‐scale this technique. Incorporating design features that mitigate drivers of mortality could increase coral‐seeding effectiveness. Here we tested five ceramic seeding‐device designs that incorporated various features intended to act as coral microrefugia. Devices seeded with Acropora tenuis spat were deployed to three sites on a shallow mid‐shelf reef on the central Great Barrier Reef (GBR), and survival was assessed after 219 days. Average yield (device‐level survival) was moderate across the device designs (22%) and all devices performed comparably. However, there was a nearly threefold increase in survival at one site compared with the other, similar sites less than 100 m away. Assessment of the benthic community around each device suggested that the sites hosted similar communities, although multivariate analyses identified a weak but significant positive relationship between survival and the first principal component (only 17% of variance), characterized by higher cover of sponges and epilithic algal communities. These results suggest that within‐reef scale variations (10s of meters) in environmental conditions, or variations in community constituents not investigated here (e.g. grazing fishes, mobile invertebrates), may impact the success of coral seeding. Further investigations into the drivers of coral survival at fine spatial scales, particularly abiotic conditions, are required to guide the placement of coral‐seeding devices and to predict their effectiveness.