A potential method for improving coral self‐attachment

Abstract

Coral restoration is becoming increasingly important to sustain declining reefs. The survival rate of translocated corals in restoration projects is around 65%. This rate is, however, highly variable among projects, with success ranging from 0 to 90% and with detachment being a significant cause of mortality. Improving the speed and strength of coral self-attachment would increase survivorship in translocated corals. To address this need, we tested whether fragments of the scleractinian coral Hydnophora rigida, artificially attached upside-down, would self-attach more rapidly to the substratum than those artificially attached the right way up, which is the normal practice. We also tested the effect of three different diets (unfed, normal Artemia, and lipid-enriched Artemia) on coral growth and other biological responses. After 100 days, our results demonstrated that corals fixed upside-down grew significantly wider and faster over the substratum than corals fixed the right way up. A significantly higher number of fragments fixed upside-down were also able to self-attach and grow over the substratum (87%) compared with fragments fixed the right way up (58%). Neither the buoyant weight, height increment, symbiont density, chlorophyll, maximum quantum yield nor color of corals fixed upside-down differed significantly from corals fixed the right way up. Our data show that simply inverting the orientation of coral fragments may substantially accelerate the time for self-attachment and increase the survival rate of translocated corals in restoration projects. Implications for Practice• During reef restoration, self-attachment failure is a significant cause of death in translocated corals. • Corals artificially attached upside-down self-attached faster, in higher numbers, and grew wider over substrata than corals artificially attached the right way up. • Placing corals upside-down appears to be a simple, yet effective, method for improving coral self-attachment under ex situ conditions. Nonetheless, field trials using several species are still needed. • Corals that were fed with Artemia (lipid-enriched or non-enriched) grew faster than unfed corals. Feeding might improve the survival and resilience of corals grown ex situ prior to translocation on to reefs.

Coral restoration – A systematic review of current methods, successes, failures and future directions

“…[124,125] but see [61]), and yet, in most reports, percent survival of outplants is not clearly reported in accordance to size. The metric that best illustrates the lack of standardised reporting is growth of corals, where a multitude of creative metrics have been used-including linear extension (the summed length of each individual branch within a colony [62,115,126,127], height [128], 'ecological volume' [129,130], branch width [60,131], number of branches [132][133][134], basal width [135] as well as combinations of width, length, height and partial mortality, maximum colony diameter, number of branches, and virtually every other dimension one could think of. The metrics used have such little overlap that comparisons of overall growth among studies are difficult or impossible.…”

Coralclip®: a low‐cost solution for rapid and targeted out‐planting of coral at scale

“…Numerous approaches for out‐planting asexually propagated coral fragments or sexually propagated larvae on settlement devices have been utilized (Table S1) (Gomez et al ; Boström‐Einarsson et al ). Simple “unattached” methods that connect loose fragments with line can be successful in sheltered reefs (Bowden‐Kerby ; see Forrester et al ), but most approaches need some form of secure attachment in physically dynamic reefs (Tagliafico et al ) since natural self‐attachment rates of corals to the reef are typically low (Smith & Hughes ; Guest et al ). By far the most commonly used approaches are chemical adhesives (glue, epoxy; Dizon et al ; Gomez et al ; cement, Forrester et al ; Kotb ) as well as physical attachment to masonry nails using cable ties (Okubo et al ; Forrester et al ; ; Goergen & Gilliam ) or metal plates/wire (Endo et al ), but also to wooden stakes using fishing line (Dela Cruz et al ).…”

Novel infrastructure for coral gardening and reefscaping

“…It is important that the fragment's tissue has grown over the tiles prior to outplanting, as the adhesion of the adhesive often wears off over time. It has been shown that coral fragments from branching species attached upside down grew significantly wider and faster over the tiles than corals attached right side up (Tagliafico et al, 2018), and we recommend this technique to promote rapid tile overgrowth.…”