Diaz-Pulido, Guillermo, Reyes-Nivia, Catalina, Adame, Maria Fernanda, Arthingotn, Angela H., Collier, Catherine, and Lovelock, Catherine (2024) Question 4.2 What are the measured impacts of nutrients on Great Barrier Reef ecosystems, what are the mechanisms for those impacts and where is there evidence of this occurring in the Great Barrier Reef? Report Section. Department of Climate Change, Energy, the Environment and Water, Townsville, QLD, Australia.

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Abstract

In the Great Barrier Reef, dissolved inorganic nutrient availability typically decreases from inshore to offshore areas with the highest concentrations found between Cooktown and Gladstone in waters influenced by river plumes. Dissolved inorganic nutrients are critically important for the overall health and condition of Great Barrier Reef ecosystems but if they occur in excessive amounts, nutrients can have a detrimental effect. The most severe impacts of increased nutrients on corals may be indirect. For instance, elevated nutrient availability on inshore reefs is generally (but not always) positively correlated with increased fleshy macroalgal abundance. High fleshy macroalgae abundance and biomass can reduce coral settlement and recruitment, outcompete corals, reduce coral cover and negatively affect coral calcification. Another indirect effect is the relationship between excess nutrients and increasing phytoplankton food supplies for crown-of-thorns starfish larval stages which can potentially contribute to outbreaks. Direct effects of elevated nutrients include reduced coral calcification, negative impacts on coral reproduction, and potentially lowering thermal tolerance to bleaching. Links between elevated nutrients and other impacts such as coral disease, microbioerosion and microbial communities are variable between studies and locations and require further investigation. There is no clear evidence of direct negative impacts of increased dissolved inorganic nutrients on seagrass ecosystems, and although elevated nutrients may be beneficial for mangrove growth, they can interact with climate stressors such as drought (low rainfall and low humidity) causing mangrove decline. There is limited evidence of the impact of dissolved inorganic nutrients on Great Barrier Reef wetland ecosystems. Regional and basin-specific management of nutrient runoff from the Great Barrier Reef catchment area should remain a priority to support inshore marine ecosystems.

Item ID:	93635
Item Type:	Report (Report Section)
Copyright Information:	© Commonwealth of Australia, as represented by the Department of Climate Change, Energy, the Environment and Water, 2024.
Date Deposited:	03 Sep 2026 07:08
FoR Codes:	41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410402 Environmental assessment and monitoring @ 50% 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 50%
SEO Codes:	18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180501 Assessment and management of benthic marine ecosystems @ 50% 18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180505 Measurement and assessment of marine water quality and condition @ 50%
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