Restricted terrestrial carbon input to the continental shelf during Cyclone Winifred: implications for terrestrial runoff to the Great Barrier Reef Province

Tropical Cyclone Winifred (1 February 1986) provided an ideal opportunity to examine the fate of high river discharge in the Central Great Barrier Reef by producing near-record floods between Townsville and Cairns. Comparison of the carbon isotope ratio of organic matter in shelf sediment collected immediately before and after the cyclone showed that the bulk of terrestrial plant detritus from the Johnstone River was deposited within 2 km of the rivermouth and none moved more than 15 km offshore. By comparing the magnitude of the Johnstone River flow to the maximum recorded flows on other rivers in the Great Barrier Reef Province, we conclude that terrestrial runoff has not reached the Reef in historical times except, perhaps, during rare Burdekin River floods. Terrestrial detritus initially deposited near chore, however, is resuspended during tropical cyclones and may eventually be transported to the Reef.