Multi-year evaluation of rearing techniques for three sexually propagated Caribbean corals in a restoration setting
Sexual propagation is a promising coral‑restoration strategy, yet high post‑settlement mortality limits its scalability. In St. Croix, U.S. Virgin Islands, researchers compared three rearing investments—direct outplanting, in situ field nurseries and ex situ aquaculture—for three Caribbean species. After one year of rearing and three years of monitoring, survival remained low (0–1.8%), but corals reared in in situ nurseries had markedly higher survival and lower cost per seeding unit than other methods. These results show that nursery stages can improve long‑term outcomes, though low survival on degraded reefs underscores the need for continued innovation in coral‑restoration strategies.
Subject Tags
- Habitat restoration
- Reefs
Abstract
In response to declining coral populations worldwide, conservation groups are increasingly applying restoration strategies to bolster abundance and diversity, including sexual propagation of corals. Collection and fertilization of coral gametes as well as larval rearing and settlement have been successful. However, post-settlement stages remain a bottleneck (80–100% mortality), which makes this technique costly to implement at scale. To address this challenge, we compared the survival and colony size of three sexually propagated Caribbean coral species, Diploria labyrinthiformis, Pseudodiploria strigosa, and Orbicella faveolata, reared at three levels of investment: direct outplant to reef, in situ field nursery rearing and ex situ aquaculture facility rearing. As part of coral sexual propagation work in St. Croix, United States Virgin Islands, recruits were reared for one year before being outplanted to reef plots and were monitored annually for three subsequent years. The cost-effectiveness of each rearing strategy was calculated at each monitoring time point via coral seeding unit yield and cost per seeding unit. Although survival was low at four years (0–1.8%), corals reared in the in situ nursery displayed significantly higher survival and therefore lower cost per seeding unit than the other two investment strategies. These results highlight the benefits of an in situ nursery stage to increase long-term juvenile survival and cost-effectiveness. The return on investment of corals reared in the in situ nursery suggests that outplanting sexually propagated corals may be a viable restoration strategy; however, the low proportion of corals surviving at 4 years highlights current limitations when outplanting on degraded reefs.
Citation
Nixon, E. N., Gutting, A. N., Cook, S., Wegley Kelly, L., & Lillis, A. (2025). Multi‐year evaluation of rearing techniques for three sexually propagated Caribbean corals in a restoration setting. Restoration Ecology, 33(4), e70039. https://doi.org/10.1111/rec.70039
TNC Authors
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Emily N. Nixon
The Nature Conservancy -
Alexandra N. Gutting
The Nature Conservancy -
Sophie Cook
The Nature Conservancy -
Ashlee Lillis
The Nature Conservancy