Marine Science Faculty Publications

Amphistegina (Foraminiferida) Densities as a Practical, Reliable, Low-Cost Indicator of Coral Reef Vitality

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Conference Proceeding

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Algal symbiont-bearing foraminifera, Amphistegina spp., can provide a practical, reliable, low-cost indicator of coral-reef vitality. These protists are relatively large (1-3 mm adult diameter), reef-dwellers found nearly circumtropically. In their dependence upon algal endosymbionts for growth and calcification, their adaptation to nutrient-poor, warm, shallow-water environments is similar to that of reef-building corals. They live on reefrubble and on closely-cropped coralline and filamentous algae on reef substrate. When environmental conditions change to favor organisms using autotrophic and heterotrophic nutritional modes over organisms using mixotrophic (algal symbiotic) modes, Amphistegina populations decline.

Diatom endosymbionts impart a golden-brown to olive-green color to living Amphistegina specimens, making them easy to recognize. These foraminifera can be sampled by collecting reef rubble, scrubbing it, and examining the detached sediment and meiobiota with stereomicroscope, either live or freeze-killed and dried. Under "healthy" reef conditions, Amphistegina population densities should exceed 50 living individuals per 100 cm2 bottom area of rubble. Population densities of 10-50/100 cm2 indicate cause for concern. Under environmental conditions marginal for reef growth, Amphistegina may be present but uncommon (less than 10/100 cm2 of rubble.) Living specimens are usually not found in areas where rapid reef degradation is occurring.

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Citation / Publisher Attribution

Amphistegina (Foraminiferida) Densities as a Practical, Reliable, Low-Cost Indicator of Coral Reef Vitality, in M. P. Crosby, G. R. Gibson Jr. & K. W. Potts (Eds.), A Coral Reef Symposium on Practical, Reliable, Low Cost Monitoring Methods for Assessing the Biota and Habitat Conditions of Coral Reefs, U.S. Environmental Protection Agency, p. 37-44