Abstract
In December 2010, the highest recorded Queensland rainfall associated with Tropical Cyclone ‘Tasha’ caused flooding of the Fitzroy River in Queensland, Australia. A massive flood plume inundated coral reefs lying 12 km offshore of the Central Queensland coast near Yeppoon and caused 40–100% mortality to coral fringing many of the islands of Keppel Bay down to a depth of ∼8 m. The severity of coral mortality was influenced by the level of exposure to low salinity seawater as a result of the reef's distance from the flood plume and to a lesser extent, water depth and whether or not the reef faced the plume source. There was no evidence in this study of mortality resulting from pollutants derived from the nearby Fitzroy Catchment, at least in the short term, suggesting that during a major flood, the impact of low salinity on corals outweighs that of pollutants. Recovery of the reefs in Keppel Bay from the 2010/2011 Fitzroy River flood is likely to take 10–15 years based on historical recovery periods from a similar event in 1991; potentially impacting visitor numbers for tourism and recreational usage. In the meantime, activities like snorkeling, diving and coral viewing will be focused on the few shallow reefs that survived the flood, placing even further pressure on their recovery. Reef regeneration, restoration and rehabilitation are measures that may be needed to support tourism in the short term. However, predictions of a warming climate, lower rainfall and higher intensity summer rain events in the Central and Coastal regions of Australia over the next decade, combined with the current anthropogenic influences on water quality, are likely to slow regeneration with consequent impact on long-term reef resilience.
Highlights
Cyclonic rain events are an intrinsic factor shaping the nature, location and extent of inshore coral reefs of the Great Barrier Reef (GBR)
We report the impacts of a record rainfall event associated with Cyclone ‘Tasha’ on southern GBR inshore reefs in Keppel Bay and investigate some of the spatial, temporal and environmental factors potentially contributing to the severity of these impacts
Salinity levels at the study sites before the flood were between 33–35 practical salinity units (PSU) (Fig 3) Keppel Bay reef flat and slope salinity levels lagged Fitzroy River average daily discharge levels by,9 days with average daily salinities below 30 PSU at Halfway Island (6 m, reef slope) occurring for,3 weeks between 1 January and 23 January 2011
Summary
Cyclonic rain events are an intrinsic factor shaping the nature, location and extent of inshore coral reefs of the Great Barrier Reef (GBR). Because of the inherent difficulties in monitoring reefs during conditions of high turbidity caused by sediment resuspension, few studies have investigated the spatial pattern and extent of their short term impact. Natural disturbance events such as floods are not currently incorporated into reef management decisions but given their potential for shaping the nature of inshore reefs, understanding the patterns and severity of flood impacts can inform predictions of recovery that help assess the potential effects on industries such as local tourism as well as conservation efforts
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