Institut de Recherche pour le Développement (IRD), LEMAR - UMR 6539 (UBO, CNRS, IRD, IFREMER), BP A5, 98848, Nouméa cedex, New Caledonia.
Laboratoire d'Excellence CORAIL, ENTROPIE (UMR9220), IRD, 98848, Nouméa cedex, New Caledonia.
Sci Rep. 2017 Jun 16;7(1):3721. doi: 10.1038/s41598-017-03781-y.
Seabirds concentrate nutrients from large marine areas on their nesting islands playing an important ecological role in nutrient transfer between marine and terrestrial ecosystems. Here we investigate the role of guano on corals reefs across scales by analyzing the stable nitrogen isotopic (δN) values of the scleractinian coral Pocillopora damicornis on fringing reefs around two Pacific remote islets with large seabird colonies. Marine stations closest to the seabird colonies had higher nitrate + nitrite concentrations compared to more distant stations. Coral and zooxanthellae δN values were also higher at these sites, suggesting that guano-derived nitrogen is assimilated into corals and contributes to their nitrogen requirements. The spatial extent of guano influence was however restricted to a local scale. Our results demonstrate that seabird-derived nutrients not only spread across the terrestrial ecosystem, but also affect components of the adjacent marine ecosystem. Further studies are now needed to assess if this nutrient input has a positive or negative effect for corals. Such studies on remote islets also open fresh perspectives to understand how nutrients affect coral reefs isolated from other anthropogenic stressors.
海鸟在其筑巢岛屿上将来自大片海洋区域的营养物质集中起来，在海洋和陆地生态系统之间的营养物质转移中发挥着重要的生态作用。在这里，我们通过分析两个太平洋偏远岛屿周围边缘珊瑚礁上的石珊瑚（Pocillopora damicornis）的稳定氮同位素（δN）值，来研究海鸟粪便在不同尺度上对珊瑚礁的作用。与更远的站点相比，靠近海鸟聚居地的海洋站点硝酸盐+亚硝酸盐浓度更高。这些地点的珊瑚和共生藻的 δN 值也更高，这表明海鸟粪便中的氮被同化到珊瑚中，并有助于满足其氮需求。然而，海鸟粪便影响的空间范围仅限于局部尺度。我们的研究结果表明，海鸟衍生的营养物质不仅在陆地生态系统中传播，而且还会影响到相邻的海洋生态系统的组成部分。现在需要进一步研究来评估这种养分输入对珊瑚是有益还是有害。对偏远岛屿的研究也为了解营养物质如何影响与其他人为胁迫因素隔离的珊瑚礁提供了新的视角。
