Evaluating Methods for Transplanting Endangered Elkhorn Corals in the Virgin Islands

Abstract

Restoration of rare corals is desirable and restoration projects are fairly common, but scientific evaluation of this approach is limited. We tested several techniques for transplant and restabilization of Acropora palmata (the elkhorn coral), an ecologically important Caribbean coral whose populations have suffered severe declines. In rough weather, fragments break-off colonies of branching corals like A. palmata as a normal form of asexual reproduction. We transplanted naturally produced coral fragments from remnant populations to nearby restoration sites. Untouched control fragments at the donor site died faster and grew slower than fragments attached to the reef, so attaching fragments to the reef is beneficial. Transplanted fragments grew and died at a rate similar to fragments left at the donor site (both groups were attached to the reef), so there were no effects of moving fragments or differences in habitat quality between donor and restoration sites. Growth and survival were similar using four methods of attaching fragments to the reef: cable ties, two types of epoxy resin, and hydrostatic cement. Corals sometimes compete with the macroalgae that dominate degraded reefs, and clearing surrounding algae improved the growth of fragments. After 4 years, transplanted fragments grew to 1,450 cm 2 in area and so were potentially sexually active. Because the methods tested are simple and cheap, they could be used by volunteer recreational divers to restore locally extirpated A. palmata populations or to enhance reefs where natural recovery is slow.

Assessing an abridged nursery phase for slow growing corals used in coral restoration

“…Responding to the decline of reef ecosystems, various coral reef rehabilitation techniques have been developed (Jaap, 2000;Raymundo et al, 2007; transplantation protocols employed at various locations, worldwide, have resulted in varying degrees of success (measured as increased coral coverage and fish assemblages) as well as different degrees of damage incurred by donor colonies and of stress inflicted on the transplant materials Ward, 2008, 2012;Lirman et al, 2010;Forrester et al, 2011Forrester et al, , 2013Gomez et al, 2011Gomez et al, , 2014Young et al, 2012).…”

Coral Growth Assessment on an Established Artificial Reef in Antigua

“…Although transplantation stress may be a factor causing lower than normal growth rates, RBF adheres to strict protocols and ethical guidelines when handling corals to reduce stress (Barber et al 2007), and Forrester et al (2011) show no adverse impact on growth rate from handling or transplanting stress on similar species in a similar system using similar techniques. These findings lead us to believe that the restoration environment likely played a relatively large role in the observed growth rate variation, though we acknowledge the possibility that other factors, such as temporal variability in growth rate (Bak et al 2009) may also be of concern.…”

“…Overall, the Caribbean has experienced an 80% loss of coral cover since 1975 (Wilkinson 2004). In the face of such degradation, actively restoring coral reefs is frequently considered, but may not always be the best option (Moberg and Rönnbäck 2003, Krumholz et al 2010, Forrester et al 2011. Transplanting corals (especially imperiled corals which would otherwise die) onto restoration sites may preserve genetic variability and/or decrease the time for a restoration site to become viable habitat for many reef dwelling species (Lindahl 1998, Bowden-Kerby 2003 but long-term benefits are not well documented, and this process is time-and labor-intensive.…”

Caribbean Damselfish Recolonize Reefs Following Coral Restoration

“…The restoration site, White Bay, is near Guana Island in the British Virgin Islands (18.473°N, -64.575°W) (Forrester et al 2011). Elkhorn coral has been absent from the shallow (1-3 m depth) reefs in White Bay for at least 22 years, but based on skeletal remains and anecdotal reports, was formerly common.…”

“…Elkhorn coral has been absent from the shallow (1-3 m depth) reefs in White Bay for at least 22 years, but based on skeletal remains and anecdotal reports, was formerly common. Other live corals are also rare at the site (1.6% cover in 2005) (Forrester et al 2011). From 2005-2011 fragments of elkhorn coral were transferred to White Bay from nearby source sites and attached to the reef.…”