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. 2014 Apr;20(4):1043-54. doi: 10.1111/gcb.12369. Epub 2014 Feb 11.
Recent research efforts have demonstrated increased bioerosion rates under experimentally elevated partial pressures of seawater carbon dioxide (pCO2 ) with or without increased temperatures, which may lead to net erosion on coral reefs in the future. However, this conclusion clearly depends on the ability of the investigated bioeroding organisms to survive and grow in the warmer and more acidic future environments, which remains unexplored. The excavating sponge Cliona orientalis Thiele, is a widely distributed bioeroding organism and symbiotic with dinoflagellates of the genus Symbiodinium. Using C. orientalis, an energy budget model was developed to calculate amounts of carbon directed into metabolic maintenance and growth. This model was tested under a range of CO2 emission scenarios (temperature + pCO2 ) appropriate to an Austral early summer. Under a pre-industrial scenario, present day (control) scenario, or B1 future scenario (associated with reducing the rate of CO2 emissions over the next few decades), C. orientalis maintained a positive energy budget, where metabolic demand was likely satisfied by autotrophic carbon provided by Symbiodinium and heterotrophic carbon via filter-feeding, suggesting sustainability. Under B1, C. orientalis likely benefited by a greater supply of photosynthetic products from its symbionts, which increased by up to 56% per unit area, and displayed an improved condition with up to 52% increased surplus carbon available for growth. Under an A1FI future scenario (associated with 'business-as-usual' CO2 emissions) bleached C. orientalis experienced the highest metabolic demand, but carbon acquired was insufficient to maintain the sponge, as indicated by a negative energy budget. These metabolic considerations suggest that previous observations of increased bioerosion under A1FI by C. orientalis may not last through the height of future A1FI summers, and survival of individual sponges may be dependent on the energy reserves (biomass) they have accumulated through the rest of the year.
最近的研究工作表明，在实验中升高海水二氧化碳分压（pCO2）和/或升高温度下，生物侵蚀率增加，这可能导致未来珊瑚礁出现净侵蚀。然而，这一结论显然取决于被研究的生物侵蚀生物在未来更温暖和更酸性的环境中生存和生长的能力，而这一点仍未得到探索。挖掘海绵 Cliona orientalis Thiele 是一种广泛分布的生物侵蚀生物，与共生的虫黄藻属 Symbiodinium 共生。利用 C. orientalis，开发了一个能量预算模型来计算代谢维持和生长所需的碳量。该模型在一系列 CO2 排放情景（温度+pCO2）下进行了测试，这些情景适用于澳大利亚初夏。在一个前工业化情景、当前（对照）情景或 B1 未来情景（与在未来几十年内降低 CO2 排放速度有关）下，C. orientalis 保持了正的能量预算，代谢需求可能通过共生的虫黄藻提供的自养碳和通过滤食获得的异养碳得到满足，这表明其可持续性。在 B1 情景下，C. orientalis 可能受益于共生体提供的光合产物供应增加，单位面积增加了高达 56%，并且状况改善，可用于生长的过剩碳增加了高达 52%。在 A1FI 未来情景（与“照常营业”的 CO2 排放有关）下，白化的 C. orientalis 经历了最高的代谢需求，但获得的碳不足以维持海绵的生存，这表明能量预算为负。这些代谢考虑表明，以前观察到的 A1FI 下 C. orientalis 生物侵蚀率增加可能不会持续到未来 A1FI 夏季的高峰期，单个海绵的生存可能取决于它们在一年的剩余时间内积累的能量储备（生物量）。
