DISPERSAL IN BENTHIC FORAMINIFERA

Benthic foraminifera are present throughout the world’s oceans, from intertidal to hadal depths. Overall, several thousand extant species are recorded of which some are exclusively shallow water forms restricted to environmental conditions typical of near-shore settings. It is intriguing to note that, even if numerous shallow water assemblages throughout the world are separated by climatic or geographic barriers, they consist of taxa which often are so similar that they are considered to represent the same morpho-species. Until recently, little effort has been made to explain how benthic foraminifera disperse. Yet understanding dispersal mechanisms is the key to understanding biogeographic patterns and the response of assemblages to environmental change over a range of spatial and temporal scales. Our previously published data from inner Oslofjord (Norway) and Florida Keys (USA), as well as new data from Sapelo Island (Georgia, USA) and the open Skagerrak suggest that foraminifera disperse by means of their propagules (including both sexually and asexually produced young). The propagules are transported passively via physical processes to a wide range of settings that extend well beyond the normal habitats colonized by conspecific adults. They may constitute a significant bank of individuals in sediments where they can survive for several months under unfavourable conditions and subsequently grow and reproduce when a suitable environment is restored. A closer understanding of foraminiferal dispersal mechanisms will, in a wider sense, help our understanding of what controls global biodiversity.