Predation on foraminifera by coral reef fish; taphonomic and evolutionary implications

Fish predation or cropping offoraminifera is widespread on coral reefs. At Eniwetok Atoll, live foraminifera are taken by herbivorous grazers that crop close to the substrate, occasionally by browsers nipping higher parts of algae, scrapers like parrot fish, and omnivores feeding on algal turfs. Carnivorous fishes do not take foraminifera, except for fossorial feeders that ingest mostly detrital tests. Planktivores take foraminifera, both oceanic planktonic species and the floating stages of certain benthic species. These feeding activities have taphonomic and evolutionary consequences onforaminifera. Fishes may damage foraminiferal tests, by chipping, gouging or scratching the tests, or they may destroy the tests altogether by dissolution or crushing. The damage could be observable in the fossil record. It may also result in the elimination of some foraminifera from the fossil record of reefs, in part by later diagenesis of weakened tests. Fishes also transport foraminifera from their life habitats to other unsuitable habitats where they may die. Foraminifera have life histories and ecologic and morphologic strategies that decrease chances of individual and population mortality. These include rapid growth and reproduction in commonly cropped habitats, regeneration of damaged tests, and various protective or defensive test morphologies. Foraminifera also occupy habitats avoided by fishes, cryptic habitats, tidepools that exclude fish, and complex habitats where fish predation is ineffectual. The impacts of foraminiferal predatorslcroppers may be evident in the evolutionary record of fossil foraminifera. Furthermore, the taphonomic processes initiated by the feeding activities may well bias the fossil record such that paleoenvironmental interpretation and correlation are difficult or, worse, erroneous. INTRODUCTION