Abstract Summary
Acropora palmata is one of the major reef-building species in the Caribbean, however it is considered endangered due to global and local threats. Efforts to remedy its status have recently focused on restoration programs using sexual recruits to maintain or increase genetic diversity. Our objective is to develop low-cost, efficient techniques for upscaling sexual recruit production. We compared the survival, growth and production costs of A. palmata sexual recruits grown under short-term (< one-month) and long-term (1 to 3 years) nursery care. For short-term nursery care, we cultured three successive generations (2015-2017) in ex-situ nurseries, and out-planted them onto a severely degraded reef four-weeks post-settlement on SECORE Seeding Units. For long-term nursery care, we cultured three successive generations in ex-situ nurseries for 1 to 3 years. The colonies were then transferred to in-situ nurseries for one more year to finally be out-planted onto a reef damaged by a ship-grounding. Survival in short-term nursery care was much lower (0.01-0.02%) than for colonies produced under long-term nursery care (95-100%). Nevertheless, coral growth was three times higher after being out-planted onto the reef than under nursery conditions. Additionally, the maintenance costs of corals in long-term nursery care are considerably higher than for those maintained short-term. Upscaling the production of sexual recruits for early-stage seeding holds promise because costs are considerably reduced, however survival rates are extremely low, at least on a degraded reef in the Mexican Caribbean. A combination of ex situ cultivation during the early developmental stages coupled with seeding after the high sea surface temperatures and hurricane seasons are over may improve survival at a moderate cost. Using these techniques, seeding could then be applied at lower costs in remote areas and on a large scale.
