These included important events such as tropical storm Isaac , which also produced waves of approximately 4 m across coral farms. During late October 2012 long-period swells from Hurricane Sandy produced 5 m NW breaking waves, in combination with bottom swells across the region, and produced Doppler estimates of 13 cm. Another important event in December2012 was tropical storm Rafael, which produced not much rain, but generated 3 – 4 m swells. Bottom swells resulted in significant sediment resuspension. During the first 9 months of 2013 Culebra Island was initially impacted by three consecutive months of very dry conditions , followed by a few significant isolated strong rainfall episodes associated to the mid-Atlantic through positioning over Culebra. These included extreme events during late March and a strong tropical wave during mid June . Then, tropical storm Chantal produced some significant rain bands over eastern Puerto Rico and Culebra, with 2.5 m-high SW swells and a monthly rainfall anomaly of 215%. Tropical storm Gabrielle produced about 18 cm of rain over Culebra in about 48 hours. Runoff impacts by recurrent storm events, particularly those associated to passing tropical storms, hydroponic grow table were magnified by the recurrent practice of the Culebra Island municipal government of clearing all vegetation across several small creeks and natural drainage channels adjacent to urban areas as a preventive measure to manage potential flooding.
The end product of such practices is extreme runoff pulse events and major erosion of ephemeral stream banks with significant concomitant turbidity impacts on costal ecosystems. In spite of hurricane and extreme rainfall impacts during 2011, A. cervicornis farming during the first year was highly successful. Corals in “A frame” units showed 84% and 78% survival rate at BTA and PSO, respectively,after the first year. Survival rate at PME reached only 57% due to significant mechanical impacts by Hurricane Irene during August 2011, which caused localized destruction of some of the farming units and significant immediate and delayed coral mortality due to SDR and a White Band Disease-like condition.Also, frequent extreme rainfall events caused recurrent sediment-laden, nutrient-loaded turbid runoff impacts.PME, as well as BTA, received substantial recurrent runoff impacts. PME farms were eventually relocated after September 2011 to an alternative site adjacent to BTA, where surviving fragments showed an outstanding recovery. Temporal and management effects significantly influenced coral colony survival rates in “A frame” units, but clone variation did not, which means that extreme rainfall events had widespread adverse impacts among all clones in the population. Most interaction effects were also highly significant.
Mean percent live tissue cover on coral farms after one year was89% at BTA, 93% at PME ,and 91% at PSO ). Coral colonies showed rapid and remarkable tissue regeneration after hurricanes and blasting impacts. This project produced important lessons for adapting future community-based coral farming and coral reefrehabilitation efforts to forecasted climate changing conditions. Lessons include aspects regarding wild population source propagule selection to maintain high genetic diversity,flood tray coral farming site selection, impacts from LBSP and the crititical significance of managing adjacent land uses, and adaptive modifications to coral farming methods to improve success under changing environmental conditions. There were also important lessons learned regarding community-based participation in coral reef management activities. Maintaining high genetic clone diversity should be a critical component of every coral aquaculture and coral reef rehabilitation project to buffer against any future impacts by disease outbreaks, other epizootics, massive bleaching or environmental variability associated to local human factors or climate change. State-of-the-art genetic characterization confirmed that the six coral clones of A. cervicornis used in coral farms in this study were different genetic individuals. Genetic diversity and structure in scleractinian corals vary significantly, reflecting the evolutionary differences between species, but also the type of genetic markers employed. Microsatellite markers were more successful at detecting weak genetic structure than mitochondrial markers, ITS or allozymes.