Abstract
Eight years ago (2007), the distribution and status of Acropora palmata was quantified throughout Los Roques archipelago in Venezuela. The aim was to produce a baseline study for this species which combined population genetics with demographic data. The results highlighted that A. palmata had the potential to recover in at least 6 out of 10 sites surveyed. Recovery potential was assumed to be high at sites with a relatively high abundance of the coral, low disease prevalence, high genetic diversity, and high rates of sexual reproduction. However, as noted, Zubillaga et al. (2008) realized recovery was still strongly dependent on local and regional stressors. In 2014 (this study), the status of A. palmata was re-evaluated at Los Roques. We increased the number of sites from 10 in the original baseline study to 106. This allowed us to assess the population status throughout the entirety of the MPA. Furthermore, we also identified local threats that may have hindered population recovery. Here, we show that A. palmata now has a relatively restricted distribution throughout the park, only occurring in 15% of the sites surveyed. Large stands of old dead colonies were common throughout the archipelago; a result which demonstrates that this species has lost almost 50% of its original distribution over the past decades. The majority of corals recorded were large adults (∼2 m height), suggesting that these older colonies might be less susceptible or more resilient to local and global threats. However, 45% of these surviving colonies showed evidence of partial mortality and degradation of living tissues. Interestingly, the greatest increase in partial mortality occurred at sites with the lowest levels of protection (n}{}{X}_{o}^{2}=5.4> {X}_{c}^{2}=4.5; df = 4, p < 0.05). This may suggest there is a positive role of small scale marine management in assisting reef recovery. We also recorded a significant reduction (n}{}{X}_{mathrm{exp}}^{2}=126.8> {X}_{mathrm{cri}}^{2}=15.5; df = 8; p < 0.05) in the density of A. palmata in sites that had previously been categorized as having a high potential for recovery. One explanation for this continued decline may be due to the fact that over the past 10 years, two massive bleaching events have occurred throughout the Caribbean with records showing that Los Roques has experienced unprecedented declines in overall coral cover. We therefore conclude that although local protection could promote recovery, the impacts from global threats such as ocean warming may hamper the recovery of this threatened species.
Highlights
The western Atlantic is the second largest coral reef bioprovince on earth (Veron, 1995)
A non-metric multidimensional scaling and analysis of similarities (ANOSIM, Clarke & Green, 1988) based on Euclidean distance was performed to test whether the average distance of local threats to the occurrence of A. palmata populations differed across management zones
Our surveys covered a total area of 6.72 km2
Summary
The western Atlantic is the second largest coral reef bioprovince on earth (Veron, 1995). In 2007, ten further sites were surveyed with the purpose of collecting demographic (i.e., abundance, size structure, partial mortality and prevalence of diseases) and genetic (i.e., allele diversity and patterns of connectivity) data (Zubillaga et al, 2008) This latter study highlighted that A. palmata had high potential of recovering in, at least, six sites of the archipelago. The urgent need of an appropriate management of Los Roques was recognized, given the rapid increase in tourism and other human activities inside this MPA (Zubillaga et al, 2008) These former conclusions, about the status of A. palmata in Los Roques, came from a limited number of sites and likely did not truly portray the status of the species at the scale of the entire MPA. We compared our results to previous assessments of the species and to levels of protection
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