Centre for Coastal Biogeochemistry Research, School of Environment Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia.
Australian Institute of Marine Science, Townsville, QLD, 4810, Australia.
Nat Commun. 2020 Mar 20;11(1):1500. doi: 10.1038/s41467-020-15278-w.
Anthropogenic nutrient discharge to coastal marine environments is commonly associated with excessive algal growth and ecosystem degradation. However in the world's largest coral reef ecosystem, the Great Barrier Reef (GBR), the response to enhanced terrestrial nutrient inputs since European settlement in the 1850's remains unclear. Here we use a 333 year old composite record (1680-2012) of N/N in coral skeleton-bound organic matter to understand how nitrogen cycling in the coastal GBR has responded to increased anthropogenic nutrient inputs. Our major robust finding is that the coral record shows a long-term decline in skeletal N/N towards the present. We argue that this decline is evidence for increased coastal nitrogen fixation rather than a direct reflection of anthropogenic nitrogen inputs. Reducing phosphorus discharge and availability would short-circuit the nitrogen fixation feedback loop and help avoid future acute and chronic eutrophication in the coastal GBR.
人为向沿海海洋环境排放营养物质通常与藻类过度生长和生态系统退化有关。然而，在世界上最大的珊瑚礁生态系统——大堡礁（GBR），自 19 世纪 50 年代欧洲人在此定居以来，其对增强的陆地营养输入的响应仍不清楚。在这里，我们使用了一个 333 年的珊瑚骨骼结合有机物质中的 N/N 复合记录（1680-2012 年），以了解沿海大堡礁的氮循环如何对增加的人为营养输入做出响应。我们的主要有力发现是，珊瑚记录显示骨骼 N/N 长期以来呈下降趋势，直至现在。我们认为，这种下降是增加沿海固氮的证据，而不是人为氮输入的直接反映。减少磷的排放和可利用性将阻断固氮反馈循环，有助于避免未来大堡礁沿海地区的急性和慢性富营养化。
