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

A new disease is afflicting Amphistegina spp., foraminifera whose shells 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 of golden-brown color (mottling to bleaching), abnormal calcification, lesions on the shell surface permitting invasion by epiphytic and boring organisms, and damage to asexual reproduction. Population densities at Conch Reef, Florida Keys, declined by 95% in 1992, recovering somewhat in 1993. The highest proportions of normal individuals were found in winter; proportions of mottled specimens increased during the spring and peaked at 60-80% of the population near the summer solstice during both years. Although cause of the disease is undetermined, field and laboratory data indicate that solar irradiance may be a factor. Whatever the cause, implications for coastal sedimentation will be serious if Indo-Pacific populations ever sustain long-term damage of the magnitude seen in the Florida Keys in 1992-93.