School of Environment and Science, and Australian Rivers Institute - Coast & Estuaries, Nathan Campus, Griffith University, Brisbane, Nathan, Queensland, 4111, Australia.
J Phycol. 2020 Aug;56(4):1039-1052. doi: 10.1111/jpy.13002. Epub 2020 May 22.
Dissolved organic carbon (DOC) released by macroalgae is important in the context of coral reef degradation as it contributes to coral mortality by promoting bacterial metabolism on the coral surface. Using experimental carbon dioxide (CO ) manipulations in outdoor flow-through tanks, we found that seawater CO enrichment enhances daily net DOC release in a range of macroalgal species in the Great Barrier Reef (Australia). There was, however, large variability in DOC release among species, light and dark conditions, and CO exposure times. Under light conditions, DOC release in the red macroalga Amansia was 15 times higher under high CO conditions compared to ambient CO , however, CO enhancement did not affect DOC production in the other species. Results from the night incubations were more consistent as three of the four species (Amansia, Lobophora, and Sargassum) enhanced DOC release when enriched with CO . DOC fluxes shifted from production in the 1-d incubations to consumption in the 19-d experiment under light conditions, suggesting an important role of bacteria in DOC balances. The results suggest that rising CO (and ocean acidification) will continue to intensify space competition in favor of the macroalgae, potentially exacerbating reef degradation and ecological phase shifts from coral to macroalgal dominance.
溶解有机碳 (DOC) 由大型藻类释放，在珊瑚礁退化的背景下非常重要，因为它通过促进珊瑚表面的细菌代谢，从而导致珊瑚死亡。我们利用室外流动水箱中的实验性二氧化碳 (CO ) 处理，发现海水 CO 富集增强了大堡礁（澳大利亚）范围内多种大型藻类物种的每日净 DOC 释放。然而，DOC 释放的物种间、光照和黑暗条件以及 CO 暴露时间存在很大的可变性。在光照条件下，与环境 CO 相比，高 CO 条件下红色大型藻类 Amansia 的 DOC 释放量增加了 15 倍，但 CO 增强对其他物种的 DOC 产生没有影响。夜间孵育的结果更加一致，因为在 CO 富集条件下，四种物种中的三种（Amansia、Lobophora 和 Sargassum）增强了 DOC 释放。DOC 通量从光照条件下 1-d 孵育中的产生转变为 19-d 实验中的消耗，这表明细菌在 DOC 平衡中起着重要作用。研究结果表明，不断上升的 CO（和海洋酸化）将继续加剧空间竞争，有利于大型藻类，可能会加剧珊瑚礁退化和从珊瑚到大型藻类优势的生态阶段转变。
