Data from: Multi-species restoration accelerates recovery of extinguished oyster reefs

1. A multi-species approach to habitat restoration may boost the key
processes (e.g. recruitment) that enable foundation species to overcome
barriers to recovery. Natural systems tend to be formed by co-occurring
foundation species whose synergy drives ecological productivity and
resilience beyond that of single foundation species. Yet, restoration
remains primarily a single-species focus enterprise where positive
interactions are seldom incorporated into planning. A multi-species
approach that prioritises species combinations to create emergent
properties for their persistence may accelerate habitat recovery and the
success of restoration programs. 2. On the largest oyster reef restoration
project in the Southern Hemisphere, we experimentally established
canopy-forming kelp to test whether they could accelerate the natural
recruitment of oysters to substrata monopolised by turf-forming algae. To
understand whether facilitation of oysters was a function of the kelp
themselves (biological facilitation) or the physical environment they
create (physical facilitation), we compared recruitment to the understorey
of living kelp and synthetic kelp mimics. 3. Despite observing high
density oyster recruitment to the turf-free underside of reef boulders
(8,300 oysters/m2), turf algae appeared to inhibit oyster recruitment to
the exposed surfaces of the reef, limiting their capacity to grow and form
complex, three-dimensional habitat. 4. Transplanted kelp, whether living
or synthetic kelp mimics, effectively reduced the biomass of turf and
enhanced oyster recruitment, creating turf-free substrata on the upper
reef surfaces with up to 26 times the oyster recruitment than turf-covered
substrata. 5. Synthesis and applications. Our results provide
proof-of-concept that incorporating the transplant of canopy-forming kelp
to reefs constructed to restore oysters is not only achievable, but may be
imperative to successfully restore oyster reefs in turf-dominated systems.
Kelp transplants supressed the turf algae that otherwise excluded oysters
from the reef surface, effectively shifting the competitive advantage
toward oyster recovery by maintaining bare substrata for oyster
recruitment. In demonstrating that co-restoring foundation species
facilitates interactions that overcome barriers to recovery, we emphasise
the need for restoration programs to incorporate the functional synergy of
overlapping foundation species into planning, so to establish emergent
properties that can accelerate the recovery of restored habitat.