Is Acropora palmata recovering? A case study in Los Roques National Park, Venezuela (original) (raw)
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Is Acropora palmata really coming back? an analysis from Los Roques, Venezuela
Ten years ago, we studied the distribution and status of Acropora palmata at archipelago Los Roques because the actual status of this species at Los Roques was unclear in this archipelago after its regional collapse. In that opportunity we aimed to produce a baseline study for this species in Los Roques combining population genetics with demographic data. At that time, our results suggested that this species had the potential to come back at least in 6 out of 10 surveyed sites. This conclusion was based upon high abundance, low disease prevalence, high genetic diversity and a dominance of sexual reproduction in these populations. However, we recognized that the potential of recovery could be hindered depending on local and regional threats. In 2014, the status of this species was re-evaluated by increasing the number of sites from 12 to 106 and by identifying and targeting local and global threats that may affect population recovery. The results from this new survey showed that A. p...
Coral restoration efforts have become accepted widely as an active management tool but still lack a realistic sense of scale, achievable goals and success indicators. Since Caribbean acroporids are listed by the IUCN as 'Critically Endangered', the general goals of restoration efforts for these taxa are to prevent localized extinction and to promote recovery of self-sustaining populations. Genetic diversity of restored populations is an important consideration regardless of propagation methods (sexual versus asexual), and recent data suggest natural levels of genetic diversity are higher than previously assumed. However, there are few guidelines on the optimal transplant density or spatial arrangement needed to trigger natural regenerative processes at larger scales. Presented here are results from ten years of Acropora restoration efforts at Laughing Bird Caye National Park, Belize, where over 59,000 nursery-grown fragments (inclusive of all three Caribbean acroporids) have been out-planted in over one hectare of degraded reef. Data were acquired on host and algal clade diversity, coral growth rates (in nurseries) and survival (for outplants), bleaching history and in-situ temperature, reproductive indicators, change in live coral cover, and in fish biomass. All of the above metrics, as well as no-take zones and community involvement, are integral components of successful Acropora recovery efforts. Discussed here are three quantifiable indicators: scale (absolute increase of coral coverage), longevity of outplants, and sexual reproduction of nursery-grown, out-planted corals. We suggest realizable goals and success indicators and offer guidance for expanding restoration efforts to new sites as well as suggestions for future monitoring needs.
tAcropora cervicornis is one of the principal reef-building organisms in the Caribbean; it is also consideredone of the most threatened coral species. Due to its ecological importance and critical status it is thefocus of many restoration and management initiatives. However, studies that quantitatively measurethe efficacy or feasibility of these efforts are mostly lacking. In this study, nursery-reared fragments ofA. cervicornis were transplanted to two reefs in Puerto Rico as part of a reef rehabilitation program, andtheir survival, growth, and branch production were measured for a year. We also evaluated the effect ofthis restoration on the dynamics and viability of the fragment populations by means of a simple model.Survival of outplanted fragments surpassed 60%. Colony growth rate varied between 0.20 ± 0.18 and0.29 ± 0.21 cm d−1(mean ± SD) whereas branch production ranged between 7.02 ± 5.72 and 11.86 ± 7.06(mean ± SD) branches per fragment per year. Survival did not vary considerably with respect to fragmentsize. In contrast, large fragments (≥25 cm) grew faster and tended to produce more branches than smallerones. Model simulations indicate that (1) in the absence of recruitment, and without any subsequenthuman intervention, restored populations will decrease below a quasi-extinction level of 25% of theinitial population size after just 3 years and (2) transplanting at least 20 colony fragments per year (12%of initial population) is sufficient to keep the restored populations above the 25% threshold. We concludethat A. cervicornis may be a feasible species for restoration projects given sustained human interventionand that transplanting fragments of at least 25 cm to reefs is an effective restoration protocol that requiresminimum effort to maintain a viable restored population of this key reef-building coral.