Junjie Reef K, Browne Nicola K, Erftemeijer Paul L A, Todd Peter A
Experimental Marine and Ecology Laboratory, Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
Department of Environment and Agriculture, Curtin University, Perth, Australia.
PLoS One. 2014 Sep 8;9(9):e107195. doi: 10.1371/journal.pone.0107195. eCollection 2014.
Sediment loads have long been known to be deleterious to corals, but the effects of turbidity and settling particles have not previously been partitioned. This study provides a novel approach using inert silicon carbide powder to partition and quantify the mechanical effects of sediment settling versus reduced light under a chronically high sedimentary regime on two turbid water corals commonly found in Singapore (Galaxea fascicularis and Goniopora somaliensis). Coral fragments were evenly distributed among three treatments: an open control (30% ambient PAR), a shaded control (15% ambient PAR) and sediment treatment (15% ambient PAR; 26.4 mg cm(-2) day(-1)). The rate of photosynthesis and respiration, and the dark-adapted quantum yield were measured once a week for four weeks. By week four, the photosynthesis to respiration ratio (P/R ratio) and the photosynthetic yield (Fv/Fm) had fallen by 14% and 3-17% respectively in the shaded control, contrasting with corals exposed to sediments whose P/R ratio and yield had declined by 21% and 18-34% respectively. The differences in rates between the shaded control and the sediment treatment were attributed to the mechanical effects of sediment deposition. The physiological response to sediment stress differed between species with G. fascicularis experiencing a greater decline in the net photosynthetic yield (13%) than G. somaliensis (9.5%), but a smaller increase in the respiration rates (G. fascicularis = 9.9%, G. somaliensis = 14.2%). These different physiological responses were attributed, in part, to coral morphology and highlighted key physiological processes that drive species distribution along high to low turbidity and depositional gradients.
长期以来，人们一直认为沉积物负荷对珊瑚有害，但浊度和沉降颗粒的影响此前尚未区分开来。本研究提供了一种新方法，利用惰性碳化硅粉末来区分和量化在长期高沉积状态下，沉积物沉降与光照减少对新加坡常见的两种浊水珊瑚（菊珊瑚和索马里角孔珊瑚）的机械影响。珊瑚碎片被均匀分布在三种处理方式中：开放对照（环境光合有效辐射的30%）、遮光对照（环境光合有效辐射的15%）和沉积物处理（环境光合有效辐射的15%；26.4毫克/平方厘米·天）。每周测量一次光合作用和呼吸作用速率以及暗适应量子产率，持续四周。到第四周时，遮光对照中光合作用与呼吸作用的比率（P/R比率）和光合产量（Fv/Fm）分别下降了14%和3 - 17%，而暴露于沉积物中的珊瑚其P/R比率和产量分别下降了21%和18 - 34%。遮光对照和沉积物处理之间速率的差异归因于沉积物沉积的机械影响。不同物种对沉积物胁迫的生理反应不同，菊珊瑚净光合产量的下降幅度（13%）大于索马里角孔珊瑚（9.5%），但其呼吸速率的增加幅度较小（菊珊瑚 = 9.9%，索马里角孔珊瑚 = 14.2%）。这些不同的生理反应部分归因于珊瑚形态，并突出了驱动物种沿高浊度到低浊度及沉积梯度分布的关键生理过程。
