Safeguarding coastal coral communities on the central Great Barrier Reef (Australia) against climate change: realizable local and global actions

Abstract

The threats of wide-scale coral bleaching and reef demise associated with anthropogenic (global) climate change are widely known. Less well considered is the contributing role of conditions local to the reef, in particular reef water quality, in co- determining the physiological tolerance of corals to increasing sea temperatures and declining pH. Here, the modelled benefit of reduced exposure to dissolved inorganic nitrogen (DIN) in terrestrial runoff, which raises the thermal tolerance of coastal coral communities on the central Great Barrier Reef (Australia), is considered alongside alternative future warming scenarios. The simulations highlight that an 80% reduction in DIN 'buys' an additional ~50-60 years of reef-building capacity for No Mitigation ('business-as-usual') bleaching projections. Moreover, the integrated management benefits provided by: (i) local reductions of ~50% in DIN contained in river loads, and (ii) global stabilisation of atmospheric CO2 below 450 ppm can help ensure the persistence of hard- coral-dominated reefscapes beyond 2100. The simulations reinforce the message that