The effects of cyclone Winifred and bioturbation on sediments and sediment fauna of coral reef lagoons on the Great Barrier Reef

Tropical cyclone Winifred (Category 3) crossed the Great Barrier Reef north of Townsville on the 1st February 1986. Sediment samples were collected from the lagoons of reefs close to the track of cyclone Winifred and at reefs at a range of distances from the cyclone track.Three reefs in the path of the cyclone (Gilby Reef, Feather Reef and Potter Reef) were sampled within six days of the cyclone. Potter Reef had been sampled for another project prior to the cyclone and was sampled a third time 6 weeks after the cyclone. Rib Reef, the most distant of the reefs from the track of the cyclone had been sampled prior to the cyclone and was sampled again 14 days and 6 weeks after the cyclone. Noggin Reef and Otter Reef were sampled only once, 6 weeks after the cyclone.Observations on topography, sediment type and surface detritus of the lagoon sediments of each reef were made at 15 second intervals from a manta board towed at 2 knots. Sediment samples were collected for faunal analysis using a corer with a internal diameter of 5.5 cm. Cores were collected at a representative site within each reef lagoon at a depth of about 10m. Four groups of five, 20 cm long cores were collected at each site. Groups of cores were collected within an area of 1m² and groups were separated by approximately 4 m.Three surface sediments samples were collected from each reef lagoon for organic carbon and organic nitrogen analyses and analysis of grain size distribution. This research was undertaken to determine whether:1. cyclones impact on the sediment and sediment fauna of reef lagoons2. the impacts of cyclones on the sediment and sediment fauna are long lasting