CASCADING DISTURBANCES IN FLORIDA BAY, USA - CYANOBACTERIA BLOOMS, SPONGE MORTALITY, AND IMPLICATIONS FOR JUVENILE SPINY LOBSTERS PANULIRUS-ARGUS

Florida Bay, the shallow lagoon separating mainland Florida and the Fl orida Keys, USA, is experiencing an unprecedented series of ecological disturbances. In 1991, following reports of other ecosystem perturbat ions, we observed widespread and persistent blooms of cyanobacteria th at coincided with the decimation of sponge communities over hundreds o f square kilometers. Juvenile Caribbean spiny lobsters Panulirus argus , among other animals, rely on sponges for shelter; the impact of spon ge loss on the abundance of lobsters and their use of shelter, in part icular, has been dramatic. The loss of sponges on 27 experimental site s in hard bottom habitat in central Florida Bay resulted in the redist ribution of juvenile lobsters among the remaining shelters, an influx of lobsters into sites where artificial shelters were present, and a d ecline in lobster abundances on sites without artificial shelters. Div er surveys of sponge damage at additional sites in central Florida Bay confirmed that the sponge die-off was widespread and its occurrence c oincided with areas that had been exposed to the cyanobacteria bloom. This cascade of disturbances has dramatically altered the community st ructure of affected hard bottom areas and demonstrates the coupled dyn amics of this shallow marine ecosystem.