Rare species of West Indian aspect in the Holocene of Liverpool Bay and their biogeographic and environmental significance

Abstract

The Gulf Stream, although not directly responsible for the mild, temperate climate of the British Isles, transports vast quantities of water across the North Atlantic Ocean. An extension of the Caribbean-Loop-Florida current system, this strong current cools and becomes more saline by evaporation as it flows NE across the North Atlantic Ocean. Nevertheless, it is able to transport benthic foraminifera across oceanic distances, the fauna around Bermuda containing many species described from the Caribbean Sea. Examining two cores taken from the shallow middle neritic Holocene Surface Sands Formation of the temperate Liverpool Bay, England, we found rare specimens of eight species recorded also from the neritic of the tropical Caribbean and subtropical Atlantic South Shelf Provinces: Asterigerina carinata, Dyocibicides biserialis, Elphidium discoidale, Nonionoides grateloupii, Quinqueloculina lamarckiana, Reussella atlantica and Sahulia conica. We are confident in our identifications of A. carinata and E. discoidale, but suggest that these names may have been applied to several cryptospecies. Some of these may have been transported on floating phytal debris, A. carinata, which supports algal symbionts, having been recorded at abyssal depths in the eastern North Atlantic. Othersmay have been transported as small propagules (proloculi). Although there may be a constant rain of such specimens into Liverpool Bay, we conclude on the basis of their rarity that the exotic species are unlikely to be able to overwinter there. We suggest, however, that these may have potential as invasive species for Liverpool Bay as climates continue to warm. This is not the earliest instance of transport of exotic species across the North Atlantic. The Late Eocene species Asterocyclina soldadoensis has been recorded from both the southern Caribbean region and offshore Ireland.