Measurements of the coelenteron pH in a reef coral, Stylophora pistillata, using microsensors, under light and dark conditions and in tissues with different dinoflagellate densities

pH measurements in the cœlenteron (pHcoel) of a reef coral, Stylophora pistillata, were performed using the microsensor technique. Seven samples grown in long-term coral culture facilities on glass slides at the Centre Scientifique de Monaco were used for this study. Measuremetns were made using motorised micromanipulator for precise movements of the microsensor on the order of micrometres. We first performed depth profiles in the polyps and in the coenosarc in tissue with a high dinoflagellate density, under light conditions to determine the variation of pHcoel. We then measured pHcoel of polyps and coenosarc at eight light intensities, from darkness to strong illumination, which allowed us to derive a pHcoel-irradiance curve and evaluate the role of photosynthesis in influencing pH in the coelenteron. Finally, we measured pHcoel in the coenosarc under light and dark conditions in two regions of interest characterised by visually different densities of dinoflagellates residing within the coral tissue: a high dinoflagellate density (HDD) tissue at the centre of the microcolonies and a low dinoflagellate density (LDD) tissue at the edge of microcolonies. For each sample, at least three replicate measurements were performed under all conditions.

采用微传感器技术，对造礁珊瑚Stylophora pistillata的消化循环腔（cœlenteron，简称pHcoel）进行pH值测量。本研究使用了7个样本，这些样本在摩纳哥科学中心的长期珊瑚培养设施中，于载玻片上培育而成。测量过程借助电动显微操作仪实现微传感器的精确移动，精度可达微米级。首先，在光照条件下，对甲藻（dinoflagellate）密度较高的珊瑚虫和共肉组织进行深度剖面测量，以确定pHcoel的变化规律。随后，在从黑暗到强光照的8种光照强度下，测量珊瑚虫和共肉的pHcoel值，据此绘制pHcoel-辐照度曲线，并评估光合作用对消化循环腔pH值的影响。最后，在光照和黑暗条件下，对珊瑚组织中甲藻密度存在明显视觉差异的两个目标区域（微菌落中心的高甲藻密度组织（HDD）和边缘的低甲藻密度组织（LDD））的共肉pHcoel值进行测量。在所有条件下，每个样本至少进行3次重复测量。