Abstract

Low-tech coral aquaculture methods have been successfully used in Culebra Island, PR, since year 2003 to propagate threatened staghorn coral (Acropora cervicornis) using variable methods. Harvested corals are currently used as part of an experimental restocking program aimed at rehabilitating bomb-cratered coral reefs. An unprecedented sea surface warming occurred during 2005 that caused extensive mortalities in Acroporid corals and was followed by mass coral bleaching. A second mass mortality event occurred during 2006. Shallow-water high-temperature tolerant strains of A. cervicornis were visually identified from wild populations, harvested and cultured to test their resistance to future warming events and their potential as source of propagules for future coral restocking and reef restoration activities. Between 2003 and 2005, coral survival rates of harvested colonies transplanted into bombarded grounds was 97%, with approximately 7-fold increases in total skeletal length, and a 9-fold increase in branch production. However, following the 2005 sea surface warming event, colony survival declined to 86% (June 2005), and further down to 69% (January 2006), and 52% (December 2006). Most of the mortality was the result of repetitive outbreaks of an unknown “white syndrome”, and increased predation by corallivore snails and fireworms. High-temperature resistant cultured colonies showed survival rates of 85-95% during the first 18 months, depending on location. Mortality was mostly the result of accidental anchoring impacts. Total skeletal length increased by 8-10-fold, and branch production by 10-12-fold. Adaptive responses in coral farming and reef restoration will be critical to keep up with climate change in the near future.

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