Habitat-setting affects biodiversity while predation determines oyster survival on experimental oyster reefs

Abstract

Foundation species are being restored into inherently variable landscapes with multiple, interspersed habitats. However, understanding of the influence of different neighbouring habitats on community assembly and the survival of restored species is limited, despite their significant potential to affect restoration outcomes. We tested how habitat-setting (being next to seagrass, seagrass and mangroves, or unvegetated sediments) and predation (by meso- and/or large predators) influenced macroinvertebrate community assembly and the survival of juvenile Sydney rock oysters (Saccostrea glomerata) on experimental oyster reef units in the Port Hacking estuary, New South Wales, Australia. Each habitat-setting produced a distinct macroinvertebrate community on experimental reefs, whereas predation had limited effects on community structure. Juvenile oysters were instead highly predated everywhere, and oyster predation was dominated by the large, transient fish Acanthropagrus australis. Our findings allow practitioners to predict and tailor the communities which establish on restored oyster reefs by strategically placing them next to different habitats. If sites have a high predation risk but require seeding for reefs to establish, then caging or complex substrates must be used to increase seeded oyster survival.