Interactive effects of ocean acidification and neighboring corals on the growth of Pocillopora verrucosa@en

The physical and chemical environment around corals, as well as their physiology, can be affected by interactions with neighboring corals. This study employed small colonies (4 cm diameter) of Pocillopora verrucosa and Acropora hyacinthus configured in spatial arrays at 7 cm/s flow speed to test the hypothesis that ocean acidification (OA) alters interactions among them. Interaction effects were quantified for P. verrucosa using three measures of growth: calcification (i.e., weight), horizontal growth, and vertical growth. The study was carried out in May-June 2014 using corals from 10 m depth on the outer reef of Moorea, French Polynesia. Colonies of P. verrucosa were placed next to conspecifics or heterospecifics (A. hyacinthus) in arrangements of two or four colonies (pairs and aggregates) that were incubated at ambient and high pCO2 (1000 µatm) for 28 days. There was an effect of pCO2, and arrangement type on multivariate growth (utilizing the three measures of growth), but no interaction between the main effects. Conversely, arrangement and pCO2 had an interactive effect on calcification, with an overall 23 % depression at high pCO2 versus ambient pCO2 (i.e., pooled among arrangements). Within arrangements, there was a 34-45 % decrease in calcification for solitary and paired conspecifics, but no effect in conspecific aggregates, heterospecific pairs, or heterospecific aggregates. Horizontal growth was negatively affected by pCO2 and arrangement type, while vertical growth was positively affected by arrangement type. Together, our results show that conspecific aggregations can mitigate the negative effects of OA on calcification of colonies within an aggregation.珊瑚周边的物理化学环境及其生理机能，均可受到与邻近珊瑚间相互作用的影响。本研究以直径4 cm的疣状杯形珊瑚（Pocillopora verrucosa）与风信子鹿角珊瑚（Acropora hyacinthus）小型群体为实验对象，在流速7 cm/s的条件下构建空间阵列，用以检验海洋酸化（Ocean Acidification, OA）可改变珊瑚间相互作用这一假说。本研究通过钙化作用（即体重变化）、水平生长速率与垂直生长速率三项指标，对疣状杯形珊瑚的相互作用效应进行量化。实验于2014年5月至6月开展，所用珊瑚采集自法属波利尼西亚茉莉亚岛外礁10米水深处。将疣状杯形珊瑚群体分别与同种个体或异种个体（风信子鹿角珊瑚）组合，设置为2个或4个群体的排布模式（成对组与聚合组），随后在环境水平与高二氧化碳分压（1000 μatm）条件下培养28天。分析结果显示，二氧化碳分压与排布模式均对多变量生长指标（即前述三项生长指标）存在显著影响，但二者的主效应间无交互作用。与之相反，二氧化碳分压与排布模式对钙化作用存在交互效应：相较于环境水平二氧化碳分压，高二氧化碳分压条件下钙化作用整体下降23%（即所有排布模式合并统计结果）。在各排布模式内部，单独培养与成对培养的同种个体的钙化作用下降34%~45%，但同种聚合组、异种成对组与异种聚合组的钙化作用未受显著影响。水平生长速率受到二氧化碳分压与排布模式的负面影响，而垂直生长速率则仅受排布模式的正向影响。综合来看，本研究结果表明，同种个体的聚合排布可缓解海洋酸化对聚合群体钙化作用的负面影响。