Doropoulos Christopher, Ward Selina, Roff George, González-Rivero Manuel, Mumby Peter J
School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia; Australian Research Council Centre of Excellence for Coral Reef Studies, St Lucia, Queensland, Australia.
School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia.
PLoS One. 2015 May 26;10(5):e0128535. doi: 10.1371/journal.pone.0128535. eCollection 2015.
Tropical reefs are dynamic ecosystems that host diverse coral assemblages with different life-history strategies. Here, we quantified how juvenile (<50 mm) coral demographics influenced benthic coral structure in reef flat and reef slope habitats on the southern Great Barrier Reef, Australia. Permanent plots and settlement tiles were monitored every six months for three years in each habitat. These environments exhibited profound differences: the reef slope was characterised by 95% less macroalgal cover, and twice the amount of available settlement substrata and rates of coral settlement than the reef flat. Consequently, post-settlement coral survival in the reef slope was substantially higher than that of the reef flat, and resulted in a rapid increase in coral cover from 7 to 31% in 2.5 years. In contrast, coral cover on the reef flat remained low (~10%), whereas macroalgal cover increased from 23 to 45%. A positive stock-recruitment relationship was found in brooding corals in both habitats; however, brooding corals were not directly responsible for the observed changes in coral cover. Rather, the rapid increase on the reef slope resulted from high abundances of broadcast spawning Acropora recruits. Incorporating our results into transition matrix models demonstrated that most corals escape mortality once they exceed 50 mm, but for smaller corals mortality in brooders was double those of spawners (i.e. acroporids and massive corals). For corals on the reef flat, sensitivity analysis demonstrated that growth and mortality of larger juveniles (21-50 mm) highly influenced population dynamics; whereas the recruitment, growth and mortality of smaller corals (<20 mm) had the highest influence on reef slope population dynamics. Our results provide insight into the population dynamics and recovery trajectories in disparate reef habitats, and highlight the importance of acroporid recruitment in driving rapid increases in coral cover following large-scale perturbation in reef slope environments.
热带珊瑚礁是充满活力的生态系统,拥有具有不同生活史策略的多样珊瑚群落。在此,我们量化了幼年(<50毫米)珊瑚种群统计学特征如何影响澳大利亚大堡礁南部礁坪和礁坡栖息地的底栖珊瑚结构。在每个栖息地,每隔六个月对永久样地和附着板进行为期三年的监测。这些环境呈现出显著差异:礁坡的大型藻类覆盖率低95%,可用附着基质数量是礁坪的两倍,珊瑚附着率也是礁坪的两倍。因此,礁坡上附着后珊瑚的存活率远高于礁坪,导致珊瑚覆盖率在2.5年内从7%迅速增加到31%。相比之下,礁坪上的珊瑚覆盖率仍然很低(约10%),而大型藻类覆盖率则从23%增加到45%。在两个栖息地的卵胎生珊瑚中均发现了正的种群补充关系;然而,卵胎生珊瑚并非导致观察到的珊瑚覆盖率变化的直接原因。相反,礁坡上珊瑚覆盖率的迅速增加是由于大量散播产卵的鹿角珊瑚幼体数量众多。将我们的结果纳入转移矩阵模型表明,大多数珊瑚一旦超过50毫米就能逃过死亡,但对于较小的珊瑚,卵胎生珊瑚的死亡率是散播产卵珊瑚(即鹿角珊瑚和块状珊瑚)的两倍。对于礁坪上的珊瑚,敏感性分析表明,较大幼体(21 - 50毫米)的生长和死亡率对种群动态有很大影响;而较小珊瑚(<20毫米)的补充、生长和死亡率对礁坡种群动态影响最大。我们的结果为不同珊瑚礁栖息地的种群动态和恢复轨迹提供了见解,并强调了鹿角珊瑚补充在驱动礁坡环境大规模扰动后珊瑚覆盖率迅速增加方面的重要性。