Differential survival of nursery‐reared Acropora cervicornis outplants along the Florida reef tract

Abstract

In recent decades, the Florida reef tract has lost over 95% of its coral cover. Although isolated coral assemblages persist, coral restoration programs are attempting to recover local coral populations. Listed as threatened under the Endangered Species Act, Acropora cervicornis is the most widely targeted coral species for restoration in Florida. Yet strategies are still maturing to enhance the survival of nursery-reared outplants of A. cervicornis colonies on natural reefs. This study examined the survival of 22,634 A. cervicornis colonies raised in nurseries along the Florida reef tract and outplanted to six reef habitats in seven geographical subregions between 2012 and 2018. A Cox proportional hazards regression was used within a Bayesian framework to examine the effects of seven variables: (1) coral-colony size at outplanting, (2) coral-colony attachment method, (3) genotypic diversity of outplanted A. cervicornis clusters, (4) reef habitat, (5) geographical subregion, (6) latitude, and (7) the year of monitoring. The best models included coral-colony size at outplanting, reef habitat, geographical subregion, and the year of monitoring. Survival was highest when colonies were larger than 15 cm (total linear extension), when outplanted to back-reef and fore-reef habitats, and when outplanted in Biscayne Bay and Broward-Miami subregions, in the higher latitudes of the Florida reef tract. This study points to several variables that influence the survival of outplanted A. cervicornis colonies and highlights a need to refine restoration strategies to help restore their population along the Florida reef tract.

Ranking 67 Florida Reefs for Survival of Acropora cervicornis Outplants

“…Yet, some reefs that were immediately adjacent to or nearby these high-survival reefs were among the worst reefs for outplant survival (Figure 2). Such results suggest that although the environmental conditions within a subregion influence outplant survival (Toth et al, 2018;van Woesik et al, 2020a), variation among reefs within a given subregion, and variation of habitats within reefs also play major roles in the probability of outplant survival.…”

“…The data were a compilation of work conducted by six different coral restoration programs that examined the survival of a total of 22,634 A. cervicornis colonies raised in nurseries and outplanted to reef habitats along the Florida reef tract between 2012(van Woesik et al, 2020a. The restoration programs were conducted by: (1) The Nature Conservancy, (2) the Mote Marine Laboratory, (3) the Florida Fish and Wildlife Conservation Commission, (4) the Coral Restoration Foundation, (5) the University of Miami, and (6) Nova Southeastern University (Supplementary Document).…”

“…One of the more difficult hurdles of coral restoration, however, is developing models that can accurately predict optimal localities for coral outplanting at a variety of spatial scales (Wirt et al, 2013;van Woesik et al, 2020a). Such models aim to determine which subregions (at the 100-km scale), reefs (at the 10-km scale), or habitats (at the 0.1-1-km scale) are most favorable for Acropora survival along the Florida reef tract.…”

“…For example, A. cervicornis colonies are most commonly found growing close to reef edges, where water-flow rates are high (D'Antonio et al, 2016), and in habitats with moderate wave energy, between 0.5 and 1.5 kJ/m 2 (van Woesik et al, 2020b). In addition, A. cervicornis outplant survival appears highest in back-reef and fore-reef habitats (van Woesik et al, 2020a). There is, however, little information on the survival of acroporids at the reef scale, even though the reef scale has been identified as the scale of highest variability in Florida (Murdoch and Aronson, 1999).…”

A framework for selectively breeding corals for assisted evolution

“…Many of the disadvantages encountered in ex situ nurseries (see above and van Woesik et al, 2020) can be avoided under in situ conditions (Fig. 10 5B…”