Pocillopora spp. growth analysis on restoration structures in an Eastern Tropical Pacific upwelling area

Abstract

Coral reefs in Culebra Bay (North Pacific of Costa Rica) are threatened by multiple anthropogenic disturbances including global warming, overfishing, eutrophication, and invasive species outbreaks. It is possible to assist their recovery by implementing ecological restoration techniques. This study used artificial hexagonal steel structures, called “spiders” to compare growth of Pocillopora spp. coral fragments of different sizes. Three initial fragment class sizes 30 were used: 2, 5 and 8 cm, with each class size having 42 initial fragments. Changes in fragment 31 length, width and area were measured monthly from January to December 2020. Results showed an overall survivorship of 70%, and no significant differences in survivorship and linear growth 33 rate were detected between class sizes. The linear growth rates are 4.49 ± 1.19 cm yr-1, 5.35 ± 34 1.48 cm yr-1 and 3.25 ± 2.22 cm yr-1 for the 2, 5 and 8 cm initial class sizes, respectively. Results do not show significant differences in growth rates between the different initial fragment sizes. However, since small fragments (2 cm) presented higher mortality during the first month, using larger fragments is recommended. In addition, coral fragments grew 48% more during the non-upwelling season, which may suggest that it might be more effective and safer to start the restoration efforts during this period.