Analysis of porewater extracted from coral heads from the central Great Barrier Reef

In March 1981, colonies (heads) of the massive coral, Porites lobata, were collected using SCUBA from Davies Reef and Britomart Reef, for analysis of the porewater within the coral skeletons. Coral heads, 15-30cm in diameter, were broken off, brought near the surface and transferred into large polyethylene tubs before being transferred onto a boat. Within 15 minutes to 2 hours of collection, the coral heads were taken out of the tubs and cleaved open. The living tissue and the band of endolithic algae were removed from the upper surface and blocks of about 1 litre in volume were removed from the head. All further handling of the coral blocks and porewater was carried out under nitrogen. Each block was placed inside a centrifuge designed to extract porewater. pH and dissolved oxygen concentration of the porewater were determined immediately after collection. The porewater was then transferred to acid-washed polypropylene bottles and frozen for nutrient analyses (phosphate, nitrate, nitrite, ammonia and silicate).Control blocks were prepared a month in advance by extracting blocks from coral heads, soaking them for a week in concentrated hydrogen peroxide, then immersing the blocks for a week in running seawater. Control water samples for analyses were obtained by soaking the blocks in ambient seawater for 2 hours and extracting the porewater as previously described. Ambient seawater samples were also collected and analysed. This study was initiated to determine whether the water in the interior of coral heads differed from the surrounding seawater and to investigate if evidence exists for nutrient regeneration and microbial respiration within the coral skeleton.

1981年3月，研究人员借助水肺潜水（SCUBA）从戴维斯礁（Davies Reef）与布里托马特礁（Britomart Reef）采集了巨型块状珊瑚——叶状滨珊瑚（Porites lobata）的群体（珊瑚头），用于分析珊瑚骨骼内部的孔隙水（porewater）。采集的珊瑚头直径为15~30厘米，先将其敲断并运至海面附近，随后转移至大型聚乙烯（polyethylene）桶中，再转运至科研船。在采集后的15分钟至2小时内，将珊瑚头从桶中取出并劈开，去除其上表面的活组织与内生藻类层，再切取体积约1升的珊瑚块。后续所有珊瑚块与孔隙水的操作均在氮气（nitrogen）环境下进行。将每块珊瑚置于用于提取孔隙水的离心机中，孔隙水的pH值与溶解氧浓度在采集后即刻测定。随后将孔隙水转移至经酸洗的聚丙烯（polypropylene）瓶中，冷冻保存以用于营养盐分析，涵盖磷酸盐、硝酸盐、亚硝酸盐、氨与硅酸盐。对照组样品于实验前一个月制备：从珊瑚头切取块体，先在浓过氧化氢（hydrogen peroxide）中浸泡一周，随后置于流动海水中浸泡一周。分析用的对照水样通过将珊瑚块置于环境海水中浸泡2小时，再按前述方法提取孔隙水获得。同时采集并分析了环境海水样品。本研究旨在探明珊瑚头内部水体与周围海水是否存在差异，并探究珊瑚骨骼内部是否存在营养盐再生与微生物呼吸作用的相关证据。