UWA School of Earth and Environment and Oceans Institute, University of Western Australia , Crawley, Western Australia , Australia ; Australian Research Council Centre of Excellence for Coral Reef Studies, University of Western Australia , Crawley, Western Australia , Australia.
PeerJ. 2015 Feb 24;3:e781. doi: 10.7717/peerj.781. eCollection 2015.
To assess the viability of high latitude environments as coral refugia, we report measurements of seasonal changes in seawater parameters (temperature, light, and carbonate chemistry) together with calcification rates for two coral species, Acropora yongei and Pocillopora damicornis from the southernmost geographical limit of these species at Salmon Bay, Rottnest Island (32°S) in Western Australia. Changes in buoyant weight were normalised to colony surface areas as determined from both X-ray computed tomography and geometric estimation. Extension rates for A. yongei averaged 51 ± 4 mm y(-1) and were comparable to rates reported for Acroporid coral at other tropical and high latitude locations. Mean rates of calcification for both A. yongei and P. damicornis in winter were comparable to both the preceding and following summers despite a mean seasonal temperature range of ∼6 °C (18.2°-24.3 °C) and more than two-fold changes in the intensity of downwelling light. Seasonal calcification rates for A. yongei (1.31-2.02 mg CaCO3 cm(-2) d(-1)) and P. damicornis (0.34-0.90 mg CaCO3 cm(-2) d(-1)) at Salmon Bay, Rottnest Island were comparable to rates from similar taxa in more tropical environments; however, they appeared to decline sharply once summer temperatures exceeded 23 °C. A coral bleaching event observed in December 2013 provided further evidence of how coral at Rottnest Island are still vulnerable to the deleterious effects of episodic warming despite its high latitude location. Thus, while corals at Rottnest Island can sustain robust year-round rates of coral growth, even over cool winter temperatures of 18°-19 °C, there may be limits on the extent that such environments can provide refuge against the longer term impacts of anthropogenic climate change.
为了评估高纬度环境作为珊瑚避难所的可行性，我们报告了对季节性海水参数（温度、光照和碳酸盐化学）变化的测量结果，以及来自西澳大利亚罗特尼斯岛（32°S）最南端地理位置的两种珊瑚物种—— Yongei 鹿角珊瑚和鹿角杯形珊瑚的钙化率。浮力变化通过 X 射线计算机断层扫描和几何估计确定的从集水区表面面积归一化。Yongei 鹿角珊瑚的伸展率平均为 51 ± 4 mm y(-1)，与其他热带和高纬度地区报道的鹿角珊瑚的速率相当。尽管季节性温度范围约为 6°C（18.2°-24.3°C），下向光强度变化超过两倍，但 Yongei 鹿角珊瑚和 P. damicornis 在冬季的平均钙化率与前一个夏季和后一个夏季相当。Yongei 鹿角珊瑚（1.31-2.02 mg CaCO3 cm(-2) d(-1)）和 P. damicornis（0.34-0.90 mg CaCO3 cm(-2) d(-1)）在罗特尼斯岛的季节性钙化率与更热带环境中类似分类群的速率相当；然而，一旦夏季温度超过 23°C，它们似乎会急剧下降。2013 年 12 月观察到的珊瑚白化事件进一步证明了罗特尼斯岛的珊瑚即使在高纬度位置，仍然容易受到间歇性变暖的有害影响。因此，尽管罗特尼斯岛的珊瑚在 18°-19°C 的凉爽冬季温度下仍能维持全年强劲的珊瑚生长速度，但这些环境可能在多大程度上能为珊瑚提供免受人为气候变化的长期影响的避难所存在限制。
