A NEW DISEASE IN REEF-DWELLING FORAMINIFERA - IMPLICATIONS FOR COASTAL SEDIMENTATION

A new disease is afflicting Amphistegina spp., foraminifera whose shel ls produce up to 90% of the sand-sized sediments in nearshore zones of some Indo-Pacific islands. Disease symptoms have been prevalent in A. gibbosa in the Florida Keys since summer 1991, and were seen in both Caribbean and Indo-Pacific species in 1992-93. Symptoms include loss o f golden-brown color (mottling to bleaching), abnormal calcification, lesions on the shell surface permitting invasion by epiphytic and bori ng organisms, and damage to asexual reproduction. Population densities at Conch Reef, Florida Keys, declined by 95% in 1992, recovering some what in 1993. The highest proportions of normal individuals were found in winter; proportions of mottled specimens increased during the spri ng and peaked at 60-80% of the population near the summer solstice dur ing both years. Although cause of the disease is undetermined, field a nd laboratory data indicate that solar irradiance may be a factor. Wha tever the cause, implications for coastal sedimentation will be seriou s if Indo-Pacific populations ever sustain long-term damage of the mag nitude seen in the Florida Keys in 1992-93.