Breaching biogeographic barriers: the invasion of Haynesina germanica (Foraminifera, Protista) in the Bahia Blanca estuary, Argentina

Large populations of the living benthic foraminifera Haynesina germanica (Ehrenberg 1840) are reported for the first time from marsh and intertidal mud flat sediments of the Bahia Blanca estuary (Argentina). Maximum abundance of living specimens was recorded in shallow intertidal environments. The species was previously recorded from many European and North American shallow-water coastal settings, but has not been documented from Argentina. Comparative faunal assemblage analysis from dated core sample material from within the Bahia Blanca estuary shows that the species has not been present for at least the last 8,200 years. This supports the hypothesis that the species has been accidentally introduced outside its natural range as a probable result of ballast water and/or shipping activities. This study is the first report of a successful invasion of non-indigenous benthic foraminifera to the South Atlantic coast of Argentina. The introduction of nonnative foraminiferal species provides new evidence that human-mediated breaching of biogeographic barriers, will ultimately result in the biotic homogenization of foraminiferal intertidal faunal assemblages.