Yahel, R. H. Steinitz Marine Biology Laboratory, The InterUniversity Institute of Eilat, ryahel@vms.huji.ac.il
Genin, A. H. Steinitz Marine Biology Laboratory, The InterUniversity Institute of Eilat, amatzia@vms.huji.ac.il

 
DIEL PATTERNS OF SUSPENDED SEDIMENTS IN CORAL REEFS: THE ROLE OF BIOGENIC MECHANISMS
 
Suspension of sediments in coral reefs is thought to be controlled by currents and waves. However, our observations suggest a major role for biogenic sources, primarily resuspension by fish. This study was carried out over a 2 yr period at 4 coral reefs and one sea-grass bed in the Red Sea. Concentrations of suspended sediments in the 100-1350 um range were measured at 0.6 m above bottom using underwater pumps. A clear diel pattern was observed at the coral reefs, but not over the sea-grass bed. Sediment concentrations were on the average 53% higher during the day than at night, while zooplankton biomass was 65% higher during night. A peak in suspended sediment concentration was usually found at dusk. No correlation was found between the quantity of suspended sediments and wind, currents or surface waves, while the diurnal increase in sediments at the coral-reefs co-varied with the density of deposit-feeding fish. Numerous other sediment-resuspending animals inhabit coral reefs, most of them are nocturnally inactive. A biogenic resuspension of sediments was observed in lakes, but not in the ocean. Wherever sediment patches are found, nearby corals and other benthic animals need to be adapted for diel shifts of sediment loads.
 
Day: Friday, Feb. 5
Time: 11:45 - 12:00pm
Location: Sweeney Center
 
Code: CS63FR1145S