Benthic foraminifera from extremely shallow-water habitats of Line Islands

The Line Islands rank among the most isolated in the tropical Pacific, hold a biogeographic key position for the translocation of taxa across the Pacific, and constitute the ultimate stepping stone for the dispersal of species from east to west and vice versa. Because benthic foraminifera have limited dispersal capabilities, these isolated stepping stones are crucial for ecological and biogeographic studies. Mapping large-scale biogeographic patterns is vital for setting conservation priorities by revealing biogeographic variability and enabling the identification of species richness hot- and coldspots. Here we present the first results of a comprehensive survey of modern benthic foraminiferal assemblages from the Line Islands and compare the foraminiferal assemblages to other regions in the Pacific Ocean. We also document the diversity and composition foraminiferal biotas from inhabited and uninhabited islands to assess the impact of anthropogenic activities.

The large number of species identified allow us to place the Line Islands into a biogeographic context and to assess the role of these remote islands as a stepping stone for the translocation of species across the Pacific Ocean. Our study provides novel insights into underlying mechanisms that promote species richness patterns in different shallow-water habitats.

The sediments analyzed includes material from the inhabited Tabuaeran Island, also known as Fanning and the uninhabited Palmyra Island. The environments of the island comprise a multitude of habitats including coral reef areas, lagoons, and algal covered shallow bays.

The foraminiferal associations from coral habitats are dominated large benthic foraminifera (LBF) such as Amphistegina, Sorites, and Peneroplis and low amounts of various miliolids. The preservation of nearshore assemblages revealed predominantly abraded and broken individuals. The assemblages from nearshore beaches and reef flats are composed of miliolids, numerous perforate-hyaline, and variable amounts of diverse LBF. The foraminiferal assemblages from algal covered beaches comprise a suite of diverse smaller miliolids and rare, mainly juvenile forms of Sorites. Our survey provides novel insight into the preservation, habitat-preferences, diversity and biogeography of benthic foraminifera across the tropical Pacific.