The art of sticking: attaching methods affect direct transplantation success

The success of coral reef rehabilitation practices is highly variable among projects and depends, in many cases, on their survivorship. While most research studies have focused on the long-term survival and growth rates of transplanted corals, short-term coral detachment is one of the principal causes of mortality in rehabilitation practices. Nonetheless, it is possible to prevent this by increasing the speed of coral self-attachment. To address this issue, we tested the efficiency of three different fasteners in attaching loose coral fragments onto two artificial substrata by assessing coral self-attachment and detachment rates in a short-term period (90 days). We transplanted 515 coral fragments from 8 species onto two substrates (glass bottles and iron rebar) using three fasteners (nylon cable tie, metal wire, and hemp rope). Generalized Linear Mixed-effect Models showed that the type of fastener, substrate, and the interactions between them were the main determinants of coral self-attachment and detachment. After 90 days, corals attached with cable ties exhibited lower detachment rates (3.80%) than corals attached with metal wire (25.28%) or hemp rope (69.27%). A higher number of fragments secured with cable ties managed to self-attach (73.42%) and grow over the substrate, compared with those secured with metal wire and hemp rope (57.3% and 30.18%, respectively).