title: Ecologically based targets for bioavailable (reactive) nitrogen discharge from the drainage basins of the Wet Tropics region, Great Barrier Reef.
abstract: A modelling framework is developed for the Wet Tropics region of the Great Barrier Reef that links a quantitative river discharge parameter (viz. dissolved inorganic nitrogen concentration, DIN) with an eutrophication indicator within the marine environment (viz. chlorophyll-a concentration, chl-a). The model predicts catchment-specific levels of reduction (%) in end-of-river DIN concentrations (as a proxy for total potentially reactive nitrogen, PRN) needed to ensure compliance with chl-a 'trigger' guidelines for the ecologically distinct, but PRN-related issues of crown-of-thorns starfish (COTS) outbreaks, reef biodiversity loss, and thermal bleaching sensitivity. The results indicate that even for river basins dominated by agricultural land uses, quite modest reductions in end-of-river PRN concentrations (∼20-40%) may assist in mitigating the risk of primary COTS outbreaks from the mid-shelf reefs of the Wet Tropics. However, more significant reductions (∼60-80%) are required to halt and reverse declines in reef biodiversity, and loss of thermal bleaching resistance.
authors.affiliation: Australian Institute of Marine Science, PMB 3, Townsville MC, QLD 4810, Australia; Centre for Tropical Water and Aquatic Ecosystem Research, JCU Townsville, QLD 4811, Australia. Electronic address: s.wooldridge@aims.gov.au.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Wooldridge
authors.affiliation: Centre for Tropical Water and Aquatic Ecosystem Research, JCU Townsville, QLD 4811, Australia.
authors.forename: Jon E
authors.initials: JE
authors.lastname: Brodie
authors.affiliation: Australian Institute of Marine Science, PMB 3, Townsville MC, QLD 4810, Australia.
authors.forename: Frederieke J
authors.initials: FJ
authors.lastname: Kroon
authors.affiliation: Department of Science, Information, Technology and Innovation, Queensland Government, Brisbane, QLD 4001, Australia.
authors.forename: Ryan D R
authors.initials: RDR
authors.lastname: Turner
mesh_terms: D000383:Agriculture; D000818:Animals; D001315:Australia; D044822:Biodiversity; D001682:Biological Availability; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D004463:Ecology / Q000379:methods; D005068:Eutrophication; D008962:Models, Theoretical; D009584:Nitrogen / Q000032:analysis* / Q000493:pharmacokinetics; D045483:Rivers / Q000737:chemistry; D013215:Starfish; D060753:Water Quality
chemical_list: D002734:Chlorophyll; D009584:Nitrogen; D000077194:Chlorophyll A
keywords: Coral bleaching; Coral health; Crown-of-thorns starfish; Nutrient enrichment; Resilience; Water quality