Griffith School of Environment &Australian Rivers Institute - Coast &Estuaries, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Queensland 4111, Australia.
School of Biology, and Aquatic Chemical Ecology Center, 950 Atlantic Dr., Georgia Institute of Technology, Atlanta, Georgia, 30332, USA.
Sci Rep. 2017 Feb 1;7:41053. doi: 10.1038/srep41053.
Many coral reefs have phase shifted from coral to macroalgal dominance. Ocean acidification (OA) due to elevated CO is hypothesised to advantage macroalgae over corals, contributing to these shifts, but the mechanisms affecting coral-macroalgal interactions under OA are unknown. Here, we show that (i) three common macroalgae are more damaging to a common coral when they compete under CO concentrations predicted to occur in 2050 and 2100 than under present-day conditions, (ii) that two macroalgae damage corals via allelopathy, and (iii) that one macroalga is allelopathic under conditions of elevated CO, but not at ambient levels. Lipid-soluble, surface extracts from the macroalga Canistrocarpus (=Dictyota) cervicornis were significantly more damaging to the coral Acropora intermedia growing in the field if these extracts were from thalli grown under elevated vs ambient concentrations of CO. Extracts from the macroalgae Chlorodesmis fastigiata and Amansia glomerata were not more potent when grown under elevated CO. Our results demonstrate increasing OA advantages seaweeds over corals, that algal allelopathy can mediate coral-algal interactions, and that OA may enhance the allelopathy of some macroalgae. Other mechanisms also affect coral-macroalgal interactions under OA, and OA further suppresses the resilience of coral reefs suffering blooms of macroalgae.
许多珊瑚礁已经从珊瑚为主转变为以大型藻类为主。由于 CO 升高导致的海洋酸化（OA）被假设有利于大型藻类而不利于珊瑚，从而导致了这些转变，但在 OA 下影响珊瑚-大型藻类相互作用的机制尚不清楚。在这里，我们表明：(i) 当三种常见的大型藻类在预测到 2050 年和 2100 年将出现的 CO 浓度下与珊瑚竞争时，它们对一种常见的珊瑚的破坏性比在当前条件下更大；(ii) 两种大型藻类通过化感作用伤害珊瑚；(iii) 一种大型藻类在 CO 升高的条件下具有化感作用，但在环境水平下则没有。从大型藻类 Canistrocarpus (=Dictyota) cervicornis 的脂溶性、表面提取物，如果这些提取物来自在升高的与环境的 CO 浓度下生长的藻体，那么对在野外生长的珊瑚 Acropora intermedia 的伤害明显更大。在 CO 升高的条件下生长时，大型藻类 Chlorodesmis fastigiata 和 Amansia glomerata 的提取物并没有更强效。我们的结果表明，OA 使海藻相对于珊瑚具有越来越大的优势，藻类的化感作用可以介导珊瑚-藻类相互作用，并且 OA 可能会增强一些大型藻类的化感作用。其他机制也会影响 OA 下的珊瑚-大型藻类相互作用，而 OA 进一步抑制了遭受大型藻类大量繁殖的珊瑚礁的恢复力。
