Nitrogen fixation rates in algal turf communities of a degraded versus less degraded coral reef
Nitrogen fixation rates in algal turf communities of a degraded versus less degraded coral reef
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DOI：
10.1007/s00338-014-1207-5
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发表时间：
2014-12-01
期刊：
影响因子：
3.5
通讯作者：
Huisman, Jef
中科院分区：
文献类型：
--
作者：
den Haan, Joost;Visser, Petra M.;Huisman, Jef
藻类群落在加勒比海的珊瑚礁上随处可见，并且通常以固定 N-2 的蓝细菌为主。然而，目前尚不清楚 (1) 草坪群落实际固定了多少 N-2 以及 (2) 哪些因素影响其 N-2 固定率。因此，我们比较了库拉双匕首岛上退化和退化程度较低的珊瑚礁地点不同深度、白天和夜间草皮群落的 N-2 固定活动。用乙炔还原法测量的 N-2 固定率在浅层（5-10 米深度）略高于深层草皮群落（30 米深度），并且白天的 N-2 固定率显着超过夜间。草皮群落的 N-2 固定率在退化和退化程度较低的珊瑚礁之间没有差异。我们的研究和早期研究的文献调查都表明，草皮群落的 N-2 固定率往往低于蓝藻垫。然而，至少在我们的研究区域，草皮群落比蓝藻垫更丰富。因此，我们的结果表明，草皮群落在珊瑚礁的氮循环中发挥着重要作用。草皮对 N-2 的固定可能会产生不良的正反馈，促进藻类草皮群落的增殖，同时加速珊瑚礁退化。
Algal turf communities are ubiquitous on coral reefs in the Caribbean and are often dominated by N-2-fixing cyanobacteria. However, it is largely unknown (1) how much N-2 is actually fixed by turf communities and (2) which factors affect their N-2 fixation rates. Therefore, we compared N-2 fixation activity by turf communities at different depths and during day and night-time on a degraded versus a less degraded coral reef site on the island of Cura double dagger ao. N-2 fixation rates measured with the acetylene reduction assay were slightly higher in shallow (5-10-m depth) than in deep turf communities (30-m depth), and N-2 fixation rates during the daytime significantly exceeded those during the night. N-2 fixation rates by the turf communities did not differ between the degraded and less degraded reef. Both our study and a literature survey of earlier studies indicated that turf communities tend to have lower N-2 fixation rates than cyanobacterial mats. However, at least in our study area, turf communities were more abundant than cyanobacterial mats. Our results therefore suggest that turf communities play an important role in the nitrogen cycle of coral reefs. N-2 fixation by turfs may contribute to an undesirable positive feedback that promotes the proliferation of algal turf communities while accelerating coral reef degradation.