Appraisal of laboratory culture experiments on benthic foraminifera to assess/develop paleoceanographic proxies

Abstract

301-321The laboratory culture studies, carried out on benthic foraminifera, with the aim to refine paleoceanographic/paleoclimatic or environmental application of benthic foraminifera, have been reviewed. The review includes studies, which refined the understanding of factors that bring out changes in benthic foraminiferal abundance, morphology and chemical composition (of the test). Additionally, studies dealing with taxonomic aspects of benthic foraminifera have also been discussed, since such studies have significantly improved application of benthic foraminifera for stratigraphic correlation. Most of the laboratory culture studies on benthic foraminifera in the early days were carried out to monitor the complete life-cycle of selected species. Such studies revealed presence of morphologically different stages in the life-cycle of single species. Thus the forms that were earlier recognized as different species were later on clubbed as developmental or ontogenetic stages of single species. Interesting relationship between mode of reproduction and coiling direction were also observed. Later on, with the growing application of foraminiferal characteristics for past climatic and oceanographic reconstruction, benthic foraminifera were maintained under controlled physico-chemical conditions in the laboratory. Such studies helped to refine the differences in the foraminiferal characteristics from physico-chemically different environments, as observed in the field. As it was proposed that the amount and type of food material is the major factor that controls the benthic foraminiferal population, numerous studies were carried out to assess the response of benthic foraminifera to different type and amount of food and oxygen concentration. Surprisingly limited laboratory culture studies have been carried out to understand the factors that govern the chemical composition of the benthic foraminiferal tests. It probably reflects the difficulties in simulating the conditions under which physico-chemical parameters can be kept constant throughout the experiment. Towards the end of 20th century application of molecular systematic analysis techniques on foraminifera started and such studies refined the evolutionary history and taxonomic position of foraminifera as well as helped recognize cryptic species. However, despite a large number of culture studies being carried out on benthic foraminifera with their paleoceanographic/paleoclimatic application in focus, still much more efforts are needed to understand the parameters affecting the benthic foraminiferal abundance, morphology and chemical composition