Infaunal characteristics of benthic foraminifera from the Muthupet Lagoon ecosystem, south-east coast of India

Abstract

A thorough review of literature showed that very little work has been carried out on foraminifera from the Muthupet Lagoon. The most notable research in this aspect has been the recent findings by Rajeshwara Rao et al. (2013), who provided an insight into the ecology of one particular species, Asterorotalia trispinosa (Thalmann, 1933). Infaunal habitat preferences of benthic foraminifera, however, have not been studied in any kind of ecosystem in India so far. It was, therefore, decided to study more on the benthic foraminifera from this important ecosystem with special emphasis on infaunal characteristics. Accordingly, three cores were manually retrieved from the lagoon at water depths ranging from 1 to 1.5 m by inserting acrylic pipes; each core was 45 cm long. The cores were sliced at 1-cm interval and all the sub-samples were rose Bengal-stained in order to establish infaunal depth preferences by species that were abundant or commonly occurring. Counts of living, dead and total populations of the species Asterorotalia spinosa, Elphidium excavatum, Ammonia tepida and Ammonia beccarii were made and their downcore variations analyzed. The results establish the presence of distinct micro-habitats in Muthupet Lagoon, controlling the populations of different species. The same species seems to prefer different infaunal depths within the lagoon, either facilitated by bioturbation or search for more hospitable oxygen conditions in the sediment.