Marine Ecology Department, Faculty of Biology & Chemistry, University of Bremen, Bremen, Germany.
Seychelles Islands Foundation, Victoria, Mahé, Seychelles.
PLoS One. 2021 Dec 7;16(12):e0260516. doi: 10.1371/journal.pone.0260516. eCollection 2021.
Coral recruitment and successive growth are essential for post-disturbance reef recovery. As coral recruit and juvenile abundances vary across locations and under different environmental regimes, their assessment at remote, undisturbed reefs improves our understanding of early life stage dynamics of corals. Here, we first explored changes in coral juvenile abundance across three locations (lagoon, seaward west and east) at remote Aldabra Atoll (Seychelles) between 2015 and 2019, which spanned the 2015/16 global coral bleaching event. Secondly, we measured variation in coral recruit abundance on settlement tiles from two sites (lagoon, seaward reef) during August 2018-August 2019. Juvenile abundance decreased from 14.1 ± 1.2 to 7.4 ± 0.5 colonies m-2 (mean ± SE) during 2015-2016 and increased to 22.4 ± 1.2 colonies m-2 during 2016-2019. Whilst juvenile abundance increased two- to three-fold at the lagoonal and seaward western sites during 2016-2018 (from 7.7-8.3 to 17.3-24.7 colonies m-2), increases at the seaward eastern sites occurred later (2018-2019; from 5.8-6.9 to 16.6-24.1 colonies m-2). The composition of coral recruits on settlement tiles was dominated by Pocilloporidae (64-92% of all recruits), and recruit abundance was 7- to 47-fold higher inside than outside the lagoon. Recruit abundance was highest in October-December 2018 (2164 ± 453 recruits m-2) and lowest in June-August 2019 (240 ± 98 recruits m-2). As Acroporid recruit abundance corresponded to this trend, the results suggest that broadcast spawning occurred during October-December, when water temperature increased from 26 to 29°C. This study provides the first published record on coral recruit abundance in the Seychelles Outer Islands, indicates a rapid (2-3 years) increase of juvenile corals following a bleaching event, and provides crucial baseline data for future research on reef resilience and connectivity within the region.
珊瑚的繁殖和连续生长对受干扰珊瑚礁的恢复至关重要。由于珊瑚幼体和幼年个体的丰度因地点和不同的环境条件而异，因此在偏远、未受干扰的珊瑚礁中评估它们可以帮助我们更好地了解珊瑚早期生活史的动态。在这里，我们首先探索了 2015 年至 2019 年间，在偏远的阿尔达布拉环礁（塞舌尔）的三个地点（泻湖、西部和东部海域）的珊瑚幼体丰度变化，该时期跨越了 2015/16 年全球珊瑚白化事件。其次，我们在 2018 年 8 月至 2019 年 8 月期间，在两个地点（泻湖、近海珊瑚礁）的沉降瓦片上测量了珊瑚幼体的丰度。2015-2016 年期间，珊瑚幼体丰度从 14.1 ± 1.2 下降到 7.4 ± 0.5 个/平方米（平均值 ± SE），2016-2019 年期间增加到 22.4 ± 1.2 个/平方米。尽管 2016-2018 年期间泻湖和西部近海地区的珊瑚幼体丰度增加了两到三倍（从 7.7-8.3 增加到 17.3-24.7 个/平方米），但东部近海地区的增加发生得较晚（2018-2019 年；从 5.8-6.9 增加到 16.6-24.1 个/平方米）。在沉降瓦片上，珊瑚幼体的组成主要由石珊瑚科（所有幼体的 64-92%）组成，并且在泻湖内部的幼体丰度比泻湖外部高 7-47 倍。2018 年 10 月至 12 月期间，珊瑚幼体的丰度最高（2164 ± 453 个/平方米），而 2019 年 6 月至 8 月期间，珊瑚幼体的丰度最低（240 ± 98 个/平方米）。由于 Acroporid 幼体的丰度与这一趋势相对应，研究结果表明，在水温从 26°C 上升到 29°C 的 10 月至 12 月期间，发生了广播式产卵。本研究首次提供了塞舌尔外岛珊瑚幼体丰度的文献记录，表明在白化事件后珊瑚幼体的快速（2-3 年）增加，并为该地区珊瑚礁恢复力和连通性的未来研究提供了关键的基线数据。
