Bleaching

[Pam Muller]

Two papers were published in late 1995 on bleaching in larger foraminifera with 
diatom endosymbionts: 

Talge, HK and Hallock, P. 1995. Cytological examination of symbiont loss in a 
benthic foraminifer, Amphistegina gibbosa. Marine Micropaleontology 26:107-113. 

Hallock, P., Talge, HK, Cockey, EM, and Muller, RG. 1995. A new disease in 
reef-dwelling foraminifera: Implications for coastal sedimentation.  Journal of 
Foraminiferal Research 25:280-286.   

To summarize: 

"Bleaching" in Amphistegina in the Florida Keys began in summer 1991 and has 
continued since, increasing in the population each spring, peaking near the 
summer solstice, and with recovery in progress by late summer and continuing 
through winter months.  Mottling and bleaching in individual forams are caused 
by progressive digestion of diatom endosymbionts, accompanied by progressive 
deterioration of the foram's cytoplasm (Talge and Hallock).  Associated 
"symptoms" include anomalous shell breakage, shell-surface lesions that permit 
invasion by microborers and epibionts, and reproductive damage including 
deformed young and sometimes failure to calcify (Hallock et al.).  Similar 
symptoms have been observed in Amphistegina spp. from the Bahamas; Jamaica; 
Heron Island, Australia; the western Australian shelf; and, to a lesser extent, 
in Belau, and Hawaii.  

If you are interested in looking for similar symptoms in Amphistegina on your 
reefs, please let me know and will send you a color photocopy of normal, mottled 
and bleached Amphistegina, collection instructions, and a copy of the Hallock et 
al. reprint.   

This problem is not insignificant.  Amphistegina is normally an abundant 
reef-dwelling organism that is found nearly circumtropically (except the eastern 
tropical Pacific).  Its shells account for substantial proportions of the 
sand-sized sediments in the coastal zones of Indo-Pacific islands (e.g., 20+% of 
Hawai'i's beach sands and 90+% of Kapingimarangi's). Loss of Amphistegina 
populations could have serious implications for coastal sedimentation in such 
areas if populations sustain long-term damage of the magnitude seen in Florida 
Keys populations over the past 5 years. 

Pamela Hallock, Professor 
Department of Marine Science 
University of South Florida 
140 Seventh Avenue S. 
St. Petersburg, FL 33701 USA 
pmuller at seas.marine.usf.edu