Nitrogen fixation rates in algal turf communities of a degraded versus less degraded coral reef

作者：den Haan Joost; Visser Petra M^*; Ganase Anjani E; Gooren Elfi E; Stal Lucas J; van Duyl Fleur C; Vermeij Mark J A; Huisman Jef

来源：Coral Reefs, 2014, 33(4): 1003-1015.

DOI：10.1007/s00338-014-1207-5

• Algal turf
• Benthic cyanobacteria
• Coral reefs
• Nitrogen cycle
• N-2 fixation

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.

• 出版日期2014-12