GEOBIOTECH: MULTIPLATFORM INVESTIGATIONS INTO THE HISTORY, GEOLOGICAL AND BIOLOGICAL CONSEQUENCES OF REEF BUILDING IN BROWARD COUNTY (FL, USA)

Coral reefs, one of the spatially, biologically, and sedimentologically most complex systems, can hardly be understood from the view point of single disciplines. Also, the spatial patterns are difficult to describe and map using a single platform. The lateral complexity is further complicated by vertical, accretionary complexity. Not every hump under the sea is a reef and it is necessary to obtain insight into the sedimentology and growth fabrics of the mapped structures. Therefore, a multidisciplinary, multiplatform project was initiated to investigate the drowned reef ridges off Broward County that harbor a rich tropical fauna.

The spatial dimensions were mapped using single-beam, multibeam, SHOALS and LADS bathymetry. Based on these data, targets were selected and cored with a hydraulic underwater drill. It was thus possible to precisely distinguish reef frameworks from sand and coquina ridges. The reef frameworks were aged using U/Th and C-dating, giving valuable information regarding sea-level history. Stable isotope ratios for O and C were investigated to obtain temperature and salinity records. A chirp subbottom profiler will obtain shallow seismic data along the drilling transect. Thus it will be possible to build a detailed map of existing present topography, hindcast topography and climate at various paleo sea-levels and use these data to predict changes due to future sea-level rise. The patterns in modern benthic fauna, which often are tied to pre-existing topography, were mapped using acoustic seabed classification based on the backscatter of single beam acoustics. The resultant maps were geostatistically enhanced and groundtruthed by Autonomous Underwater Vehicle surveys which provided georeferenced video and sidescan sonar imagery that could be correlated with the habitat maps. Quantitative information about benthic community structure was derived from AUV video transects and classical transect methods using scuba-diving. Thus it will be possible to map the spatial patterns of benthic communities on reefs over the entire Broward County. Such large-scale data sets will allow scientists from different disciplines to develop and fine-tune new technologies and will provide large datasets that allow a holistic approach to understanding the dynamics of reef systems in space in time.