Bongaerts Pim, Frade Pedro R, Hay Kyra B, Englebert Norbert, Latijnhouwers Kelly R W, Bak Rolf P M, Vermeij Mark J A, Hoegh-Guldberg Ove
1] Global Change Institute, The University of Queensland, St Lucia, QLD 4072, Australia [2] ARC Centre of Excellence for Coral Reef Studies, The University of Queensland, St Lucia, QLD 4072, Australia [3] CARMABI, Piscaderabaai z/n, PO Box 2090, Willemstad, Curaçao.
1] CARMABI, Piscaderabaai z/n, PO Box 2090, Willemstad, Curaçao [2] Department of Limnology and Bio-Oceanography, Division of Marine Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
Sci Rep. 2015 Jan 7;5:7652. doi: 10.1038/srep07652.
The composition, ecology and environmental conditions of mesophotic coral ecosystems near the lower limits of their bathymetric distributions remain poorly understood. Here we provide the first in-depth assessment of a lower mesophotic coral community (60-100 m) in the Southern Caribbean through visual submersible surveys, genotyping of coral host-endosymbiont assemblages, temperature monitoring and a growth experiment. The lower mesophotic zone harbored a specialized coral community consisting of predominantly Agaricia grahamae, Agaricia undata and a "deep-water" lineage of Madracis pharensis, with large colonies of these species observed close to their lower distribution limit of 90 m depth. All three species associated with "deep-specialist" photosynthetic endosymbionts (Symbiodinium). Fragments of A. grahamae exhibited growth rates at 60 m similar to those observed for shallow Agaricia colonies (2-3 cm yr(-1)), but showed bleaching and (partial) mortality when transplanted to 100 m. We propose that the strong reduction of temperature over depth (Δ5°C from 40 to 100 m depth) may play an important contributing role in determining lower depth limits of mesophotic coral communities in this region. Rather than a marginal extension of the reef slope, the lower mesophotic represents a specialized community, and as such warrants specific consideration from science and management.
在中光层珊瑚生态系统的测深分布下限附近，其组成、生态和环境条件仍知之甚少。在此，我们通过水下可视调查、珊瑚宿主 - 共生体组合的基因分型、温度监测和生长实验，首次对加勒比海南部的一个中光层下部珊瑚群落（60 - 100米）进行了深入评估。中光层下部区域拥有一个特殊的珊瑚群落，主要由格雷厄姆鹿角珊瑚、波形鹿角珊瑚和法氏鹿角珊瑚的“深水”谱系组成，在接近其约90米深度的分布下限处观察到了这些物种的大型群体。这三个物种都与“深度特化”的光合共生体（共生藻）相关联。格雷厄姆鹿角珊瑚的碎片在60米处的生长速率与浅海鹿角珊瑚群体的生长速率相似（约2 - 3厘米/年），但移植到100米处时出现了白化和（部分）死亡现象。我们认为，深度上温度的大幅降低（从40米到100米深度下降5°C）可能在决定该区域中光层珊瑚群落的下限深度方面起着重要的作用。中光层下部并非礁坡的边缘延伸，而是一个特殊的群落，因此值得科学和管理方面给予特别关注。
