Coral Reef Ecosystems Laboratory, School of Biological Sciences, The University of Queensland, St. Lucia, QLD, 4072, Australia; Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, St. Lucia, QLD, 4072, Australia.
Glob Chang Biol. 2013 Dec;19(12):3581-91. doi: 10.1111/gcb.12334. Epub 2013 Oct 23.
The combination of ocean warming and acidification as a result of increasing atmospheric carbon dioxide (CO2 ) is considered to be a significant threat to calcifying organisms and their activities on coral reefs. How these global changes impact the important roles of decalcifying organisms (bioeroders) in the regulation of carbonate budgets, however, is less understood. To address this important question, the effects of a range of past, present and future CO2 emission scenarios (temperature + acidification) on the excavating sponge Cliona orientalis Thiele, 1900 were explored over 12 weeks in early summer on the southern Great Barrier Reef. C. orientalis is a widely distributed bioeroder on many reefs, and hosts symbiotic dinoflagellates of the genus Symbiodinium. Our results showed that biomass production and bioerosion rates of C. orientalis were similar under a pre-industrial scenario and a present day (control) scenario. Symbiodinium population density in the sponge tissue was the highest under the pre-industrial scenario, and decreased towards the two future scenarios with sponge replicates under the 'business-as-usual' CO2 emission scenario exhibiting strong bleaching. Despite these changes, biomass production and the ability of the sponge to erode coral carbonate materials both increased under the future scenarios. Our study suggests that C. orientalis will likely grow faster and have higher bioerosion rates in a high CO2 future than at present, even with significant bleaching. Assuming that our findings hold for excavating sponges in general, increased sponge biomass coupled with accelerated bioerosion may push coral reefs towards net erosion and negative carbonate budgets in the future.
由于大气二氧化碳（CO2）的增加而导致的海洋升温与酸化，被认为是对造礁生物及其在珊瑚礁上活动的重大威胁。然而，人们对于这些全球性变化如何影响脱钙剂（生物侵蚀者）在碳酸盐预算调节中的重要作用，了解得还比较少。为了解决这个重要问题，我们在初夏的 12 周内，研究了一系列过去、现在和未来的 CO2 排放情景（温度+酸化）对挖掘海绵 Cliona orientalis Thiele, 1900 的影响，该研究在大堡礁南部进行。C. orientalis 是一种广泛分布于许多珊瑚礁上的生物侵蚀者，其体内共生有属名为 Symbiodinium 的共生甲藻。我们的研究结果表明，在工业化前情景和现今（对照）情景下，C. orientalis 的生物量产生和生物侵蚀率相似。海绵组织中的 Symbiodinium 种群密度在工业化前情景下最高，而在两个未来情景下则逐渐降低，其中在“按现状发展”的 CO2 排放情景下，海绵的生物量显著减少，出现强烈白化现象。尽管出现了这些变化，但在未来情景下，海绵的生物量产生和侵蚀珊瑚碳酸盐物质的能力都有所增加。我们的研究表明，即使出现严重白化现象，C. orientalis 在高 CO2 未来的生长速度和生物侵蚀率可能会比现在更高。假设我们的研究结果适用于一般的挖掘海绵，那么随着海绵生物量的增加和生物侵蚀率的加快，珊瑚礁可能会在未来出现净侵蚀和负碳酸盐预算的情况。
