Performance of Acropora species on the Great Barrier Reef's first coral tree nursery

Introduction The worldwide decline of coral reefs has led to the proliferation of local‐scale coral restoration projects. Active restoration using in‐water coral tree nurseries and outplanting of coral fragments is relatively new on the Great Barrier Reef (GBR) and complements traditional, passive approaches to reef protection. However, given the infancy of these methods, few studies have measured the effectiveness of coral restoration techniques, including coral nursery systems. Objectives The study aimed to assess the performance of 10 Acropora species commonly used in coral tree nurseries and evaluate the impacts of harvesting wild colonies for small‐scale coral restoration programs at Hastings Reef and Fitzroy Island in the central GBR. Methods Wild reef colonies were selected as donor colonies and harvested to create fragments for coral tree nurseries. Donor and untouched (control) wild colonies were monitored for 6 months for bleaching, predation, disease, mortality, and growth. Fragment health and growth in a nursery were compared with wild and donor colonies. Species performance within nurseries was also compared. Data were analyzed using generalized linear models. Results All species showed increased growth rates after 6 months in a nursery, with lower predation and disease than control colonies on a nearby reef. However, nursery corals exhibited higher bleaching, likely due to higher temperatures at the shallower depths where nurseries were located. Conclusions Harvesting fragments had no negative effect on donor colony health. Multiple Acropora species benefited from the nursery environment and could help maintain local diversity and increase coral abundance. Higher bleaching rates in nursery fragments indicate that thermal stress must be mitigated.