Department of Marine Science, University of Otago, Dunedin, New Zealand.
Department of Biological Sciences and Marine Research Institute, University of Cape Town, Cape Town, South Africa.
Sci Rep. 2019 Mar 12;9(1):4284. doi: 10.1038/s41598-019-41030-6.
Nutrient subsidies across ecotone boundaries can enhance productivity in the recipient ecosystem, especially if the nutrients are transferred from a nutrient rich to an oligotrophic ecosystem. This study demonstrates that seabird nutrients from islands are assimilated by endosymbionts in corals on fringing reefs and enhance growth of a dominant reef-building species, Acropora formosa. Nitrogen stable isotope ratios (δN) of zooxanthellae were enriched in corals near seabird colonies and decreased linearly with distance from land, suggesting that ornithogenic nutrients were assimilated in corals. In a one-year reciprocal transplant experiment, A. formosa fragments grew up to four times faster near the seabird site than conspecifics grown without the influence of seabird nutrients. The corals influenced by elevated ornithogenic nutrients were located within a marine protected area with abundant herbivorous fish populations, which kept nuisance macroalgae to negligible levels despite high nutrient concentrations. In this pristine setting, seabird nutrients provide a beneficial nutrient subsidy that increases growth of the ecologically important branching corals. The findings highlight the importance of catchment-to-reef management, not only for ameliorating negative impacts from land but also to maintain beneficial nutrient subsidies, in this case seabird guano.
营养物质在生态交错带的转移可以提高受纳生态系统的生产力，特别是如果这些营养物质是从富营养化生态系统转移到贫营养化生态系统。本研究表明，来自岛屿的海鸟营养物质被边缘礁上珊瑚体内的共生藻吸收，并促进了优势造礁物种——美丽鹿角珊瑚的生长。靠近海鸟聚居地的珊瑚中的虫黄藻的氮稳定同位素比值（δN）明显富集，且随着与陆地距离的增加而呈线性下降，这表明海鸟产生的营养物质被珊瑚吸收。在为期一年的互惠移植实验中，与没有受到海鸟营养物质影响的珊瑚相比，靠近海鸟聚居地的美丽鹿角珊瑚的生长速度要快 4 倍。受升高的海鸟营养物质影响的珊瑚位于一个海洋保护区内，这里有丰富的草食性鱼类种群，尽管营养物质浓度很高，但它们将有害的大型藻类控制在微不足道的水平。在这种原始环境中，海鸟粪便提供了一种有益的营养物质补贴，增加了生态上重要的分枝珊瑚的生长。这些发现强调了集水区到珊瑚礁的管理的重要性，不仅可以减轻土地带来的负面影响，而且还可以维持有益的营养物质补贴，在这种情况下就是海鸟粪便。
