The role of land-based pollution in reef ecosystem declines

Research is increasingly showing that land-based nutrients (from agriculture, sewage, and livestock rearing) and sediments can compromise coral health and reduce coral resilience to climate change impacts. However, the role of land-based pollution in the widespread loss of corals remains underexplored due to a lack of reef water quality monitoring.

We are launching projects in the Caribbean and Central Pacific that will utilize coral and reef sediment cores to track nutrient and sediment input to reefs, coral health, and reef ecosystem functioning over the past few centuries, a period of intensifying land use change. Changes in nutrient, freshwater, and terrestrial sediment input will be assessed from the stable isotope signatures of coral skeletons and will be related to various measures of coral health including growth rate, bleaching, and mortality. These changes will in turn be related to changes in human dynamics on land, including land use and land cover, population density, and fertilizer usage. This work will quantitatively assess the linkages between land use, reef water quality, and reef ecosystem health and resilience.

Another major aspect of this work is a recently-formed working group led by Katie Cramer and Loren McClenachan that is formulating pathways for integrating long-term ecological data in coral reef conservation and management via the reconstruction of decadal- to centennial-scale change in reef water quality and ecosystems along the Mesoamerican Reef.

Sediment from the Maria Creek near Mission Beach in far north Queensland heading towards the Great Barrier Reef.
Photograph: STR/AFP/Getty Images

This work will enable reef managers to set appropriate water quality targets, inform the recovery plans of coral species protected under international and national laws, and inform the selection of sites appropriate for ongoing coral restoration efforts.