Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
University of Bremen, Bremen, Germany.
Sci Rep. 2020 May 5;10(1):7541. doi: 10.1038/s41598-020-64420-7.
The exchange of metabolites between environment and coral tissue depends on the flux across the diffusive boundary layer (DBL) surrounding the tissue. Cilia covering the coral tissue have been shown to create vortices that enhance mixing in the DBL in stagnant water. To study the role of cilia under simulated ambient currents, we designed a new light-sheet microscopy based flow chamber setup. Microparticle velocimetry was combined with high-resolution oxygen profiling in the coral Porites lutea under varying current and light conditions with natural and arrested cilia beating. Cilia-generated vortices in the lower DBL mitigated extreme oxygen concentrations close to the tissue surface. Under light and arrested cilia, oxygen surplus at the tissue surface increased to 350 µM above ambient, in contrast to 25 µM under ciliary beating. Oxygen shortage in darkness decreased from 120 µM (cilia arrested) to 86 µM (cilia active) below ambient. Ciliary redistribution of oxygen had no effect on the photosynthetic efficiency of the photosymbionts and overall oxygen flux across the DBL indicating that oxygen production and consumption was not affected. We found that corals actively change their environment and suggest that ciliary flows serve predominantly as a homeostatic control mechanism which may play a crucial role in coral stress response and resilience.
环境与珊瑚组织之间的代谢物交换取决于穿过围绕组织的扩散边界层（DBL）的通量。已表明覆盖珊瑚组织的纤毛会产生涡流，从而增强停滞水中 DBL 的混合。为了在模拟环境流条件下研究纤毛的作用，我们设计了一种新的基于光片显微镜的流动室设置。在不同的电流和光照条件下，结合微颗粒测速法和高分辨率氧分布对多孔鹿角珊瑚 Porites lutea 进行了研究，其中纤毛有自然和受抑两种运动状态。在较低的 DBL 中，纤毛产生的涡流减轻了接近组织表面的极端氧浓度。在有光和纤毛受抑的情况下，组织表面的氧气过剩增加到环境水平以上 350μM，而在纤毛运动时则为 25μM。在黑暗中，氧气短缺从纤毛受抑时的 120μM 减少到纤毛活跃时的 86μM。纤毛对氧气的再分配对共生藻的光合作用效率没有影响，并且整个 DBL 的氧气通量也没有影响，这表明氧气的产生和消耗没有受到影响。我们发现珊瑚主动改变其环境，并表明纤毛流主要作为一种体内平衡控制机制，这可能在珊瑚的应激反应和恢复力中发挥关键作用。
