Assessment of the effects of the 2004 coral bleaching event at Lihou Reef National Nature Reserve (Coral Sea)

Brief description

Reefs in the Lihou Reef National Nature Reserve (NNR) were surveyed between 8-13 October 2004 in order to assess the effects of significant coral bleaching, which was observed during previous surveys in March 2004.Benthic communities on the five reefs previously surveyed (Anne Cay, Georgina Cay, Lorna Cay, Middle Cay and Turtle Cay) were resampled. An additional reef in the north west of the Reserve (Juliette Cay) was sampled along with two bommies to the north west of Anne Cay (Hermit Crab Island on AUS Chart 614).Species level data and crude abundance estimates of the benthic communities were obtained using a rapid visual assessment protocol (RAP). Video transect surveys were used to obtain rigorous abundance estimates of biota at a finer taxonomic resolution.SCUBA search surveys, along transects, were conducted to assess the impact of bleaching and to measure the prevalence of a suite of coral diseases, including White Syndrome, Black Band Disease, Brown Band Disease and Skeletal Eroding Band. A series of deeper water video tows were conducted at depths between 45m and 60m, in the lagoon area of Lihou Reef NNR and also to the north of Anne Cay. Drop camera shots were also taken at 2 locations at 27-29m. Surveys were undertaken to:1. assess the effects of coral bleaching, which was observed on sites surveyed in March 1994.2. survey deeper areas, not previously surveyed, for the presence of coral communities and to establish the extent of bleaching at depth. The Lihou Reef National Nature Reserve (NNR) is one of two protected areas in the Coral Sea region. The reserve is located in the Coral Sea 400 kilometres east of Townsville, Queensland. It was proclaimed on the 16th August 1982 under the National Parks and Wildlife Conservation Act 1975.The Coringa-Herald National Nature Reserve and Lihou Reef National Nature Reserve Management Plan states that both reserves are to be managed as strict nature reserves - World Conservation Union (IUCN) Category 1a - strict nature reserve. Such reserves are managed primarily to ensure habitats, ecosystems and native species are preserved in an undisturbed state as well as to facilitate research.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: The following is a list of references for the survey protocols used in this project:1. Benthic Rapid Assessment Protocol (RAP):DeVantier LM, De'ath G, Done TJ, Turak E (1998) Ecological assessment of a complex natural system: A case study from the Great Barrier Reef. Ecological Applications 8: 480-496.2. Video Transect Surveys:Page C, Coleman G, Ninio R, Osborne K (2001) Surveys of benthic reef communities using underwater video. Long-term Monitoring of the Great Barrier Reef, Standard Operational Procedure No. 2, Australian Institute of Marine Science, Townsville.Osborne K, Oxley WG (1997) Sampling benthic communities using video transects. pp 363-376. In: English S, Wilkinson C, Baker V (eds) Survey manual for tropical marine resources. 2nd Ed. Australian Institute of Marine Science.Other Survey Methods:SCUBA Search surveys were conducted to assess the impact of bleaching on the hard coral community, and to measure the prevalence of a suite of coral diseases. Corals from the family Acroporidae were hardest hit by the bleaching event, so studies of the impact of the bleaching event and of the recovery focused on this family. Corals of the family Acroporidae were classified by growth morphology (tabular, digitate, corymbose, branching, bottlebrush and bushy). A number of other easily recognisable genera (Pocillopora, Symphylia, Montastrea and Porites lichen) were also included in these surveys, although these generally occurred in low abundance.The prevalence of disease and the effects of bleaching were estimated from three haphazardly placed 50 x 1m belt transects at each site. Transects followed depth contours at 6-9m depth and there was a minimum of 5m between transects. Colony status (healthy, dead or suffering partial mortality), and the presence of bleaching or disease were recorded. The abundance of the corallivorous snail, Drupella, was also recorded. The category "Dead coral" referred to colonies that appeared to have died since the previous survey, based on the limited algal over-growth and lack of deterioration of branches and corallites.Towed Video surveys focused on depths below 30m and into the deeper waters of the lagoon (70m on the chart). A vane-mounted and winch-controlled towed colour video camera provided visual images of the benthos to a shipboard tape recorder that was also recording GPS data (true position (WGS84), ground speed, true heading, date and time) and depth from the ships sounder. A computer based application for recording substrate, benthos and individual organisms was linked to these instruments to facilitate real-time georeferencing of all data points. Spatial resolution was ~3m at a nominal tow speed of 3km/h. C-MapTM vector charts and MaxseaTM electronic navigation software were used to monitor and record the ship's track and the depth.Drop Camera surveys used a 5 megapixel digital still camera with external strobe and a live-feed video camera mounted on a tripod. The camera was set to record a still image at 1-minute intervals. This equipment was lowered from the stern of the vessel. The video image was used to position the tripod on the substrate in order to record still images.

Notes

Credit
Sweatman, Hugh PA, Dr (Custodian)