盾形陀螺珊瑚与根枝藻和点斑篮子鱼之间相互作用的实验研究

Experimental study on competitive interaction among reef-building coral Turbinaria peltata,Rhizoclonium sp. and rabbitfish Siganus guttatus

本研究通过120d的室内培养实验研究了盾形陀螺珊瑚（Turbinaria peltata）、根枝藻（Rhizoclonium sp．）和点斑篮子鱼（Siganus guttatus）之间的相互作用关系．结果显示，高质量浓度的NO3-（5．00～10．00mg／dm3）刺激了丝状绿藻根枝藻在缸内的爆发式生长，在实验27d时根枝藻在缸壁的面积覆盖率达到90．5％，藻丝长度为10～15cm．在海藻的胁迫作用下，盾形陀螺珊瑚的PSⅡ最大光化学量子产量（Fv／Fm）均值逐渐从0．712降至0．626，降幅为10．7％～13．5％．放入4尾4～6cm长的点斑篮子鱼后，实验缸壁根枝藻的面积覆盖率在2d内从90．5％下降至10．0％．但解除根枝藻胁迫后盾形陀螺珊瑚的Fv／Fm值并没有明显变化，与对照组的差异也不显著；随着海藻胁迫因子的消除，盾形陀螺珊瑚的Fv／Fm值逐渐升高，并在第120天时恢复至初始状态．本研究结果从珊瑚光合作用效率的角度验证了啃食者的存在确能缓解富营养化对造礁珊瑚的不利影响，为“下行控制假说”提供了新的证据．

A 120 days experiment was conducted in the aquarium to study competitive interaction among reef-building coral Turbinaria peltata, green macroalgae Rhizoclonium sp. and rabbiffish Siganus guttatus. The results showed that high concentration of NO; （5.00 - 10.00mg/dm3 ） stimulated the explosive growth of filamentous Rhizoclonium sp. ,which covered 90.5% of aquarium wall on the 27th day. The length of algal filament ranged from 10cm to 15cm . Some polyps of T. peltata were covered by algae or were continuously touched and squeezed by algal filament under the action of water flow. In the meantime ,the mean Fv/Fm gradually declined from 0. 712 to 0. 626 under the stress. The addition of 4 rabbitfish sharply reduced the coverage of filamentous macroalgae from 90.5 % to 10.0 % level in 2 days, but the Fv/Fm of T. peltata didn＇t recover fast. However, as the stress on the algae disappeared, T. peltata Fv/Fm gradually returned back to initial state on day 120. The study verifies that the grazers indeed alleviate the negative effects of eutrophication on corals and it provides a new evidence for the ＂top-down control＂ of herbivores.