Shell malformation in stressed Amphistegina populations: relation to biomineralization and paleoenvironmental potential

• Published in: Marine micropaleontology Vol. 34; no. 1; pp. 107 - 115
• Main Authors: Toler, Strawn K, Hallock, Pamela
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-06-1998
• Subjects: Amphistegina; biomineralization; coral reefs; environmental change; foraminifera; Marine; ASW, USA, Florida, Florida Keys; foraminifera; biomineralization; coral reefs; environmental change
• ISSN: 0377-8398; 1872-6186
• DOI: 10.1016/S0377-8398(97)00043-1

Beginning in summer 1991 and continuing through 1996,
Amphistegina populations in the Florida Keys and elsewhere have exhibited symptoms of stress. Previous studies have reported progressive loss of symbiont color in most adult individuals during spring and summer months. In addition, commonly 15–35% of living individuals in afflicted populations have malformed tests that are chipped, broken, or broken and repaired, in contrast to approximately 5% of the living individuals in populations sampled during the 1970's and 1980's. This study illustrates observed malformations including test breakage, uneven external surfaces, abnormal shapes, bioerosion, and loss of outer chambers. Internal anomalies include poorly defined pore cups, excessive calcification, and minimal organic matrix. Previous cytological studies of these stressed
Amphistegina revealed loss of Golgi apparatus and endoplasmic reticulum. Because these organelles are sites of glycoprotein and glycosaminoglycan synthesis, we postulate that reduced synthesis of these major organic matrix components of the foraminiferal shell may account for the observed biomineralization anomalies. Documentation of these anomalies can provide the basis for determining if similar stress events occurred in the fossil record.