Coral skeletons reveal the history of nitrogen cycling in the coastal Great Barrier Reef

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 1850s remains unclear. This study uses a 333-year-old composite record (1680-2012) of ¹⁵N/¹⁴N in coral skeleton-bound organic matter to understand how nitrogen cycling in the coastal GBR has responded to increased anthropogenic nutrient inputs. The coral record shows a long-term decline in skeletal ¹⁵N/¹⁴N towards the present, suggesting increased coastal nitrogen fixation rather than a direct reflection of anthropogenic nitrogen inputs. The authors argue that reducing phosphorus discharge would help avoid future eutrophication.

Dirk V. Erler, Hanieh Tohidi Farid, Thomas D. Glaze, Natasha L. Carlson-Perret, Janice M. Lough