Climate change doubles sedimentation-induced coral recruit mortality.

ABSTRACT

Coral reef replenishment is threatened by global climate change and local water-quality degradation, including smothering of coral recruits by sediments generated by anthropogenic activities. Here we show that the ability of Acropora millepora recruits to remove sediments diminishes under future climate conditions, leading to increased mortality. Recruits raised under future climate scenarios for fourteen weeks (highest treatment +1.2 °C, pCO2 950 ppm) showed twofold higher mortality following repeated sediment deposition (50% lethal sediment concentration LC50 14-24 mg cm-2) compared to recruits raised under current climate conditions (LC50 37-51 mg cm-2), depending on recruit age at the time of sedimentation. Older and larger recruits were more resistant to sedimentation and only ten-week-old recruits grown under current climate conditions survived sediment loads possible during dredging operations. This demonstrates that water-quality guidelines for managing sediment concentrations will need to be climate-adjusted to protect future coral recruitment.