Ecological transitions indicated by foraminiferal assemblages in paralic environments

The foraminiferal assemblages of about 1,500 samples collected worldwide in various types of paralic environments, supplemented by selected published data, led to the determination of several species assemblages typical of paralic subenvironments. These assemblages are shown on a series of models, giving a view of the response of foraminifera to a variety of gradients in different situations. Given the proposed models, it should be possible to go to a new environment, and based on the assemblage found, determine the average characteristics of the paralic subenvironment. Three main biotic trends are evident from oceanic to continental end members, and are related to marine-to-freshwater transition where freshwater input is sufficient or marine-to-hypersaline water in inverse estuaries; to marine-to-confined water transition in choked tropical and Mediterranean lagoons; and to water-to-land transition from shallow subtidal zones up to marshes in all kinds of environments. On the basis of these results, a ternary diagram is proposed, where paralic environments can be plotted according to their dominant characteristic.