Foraminiferal population dynamics on elevated plastic substrates and in sediments at 4000 m in the Eastern Pacific

Abstract

Although plastics are becoming more prevalent, even in the far reaches of the deep sea, the influence of these novel attachment surfaces has yet to be systematically studied regarding the ecology and distribution patterns of attached fauna. Herein, we report the abundances and vertical distribution patterns of epibenthic foraminifera living on plastics after 2 yr on the seafloor at 4000 m water depth and compare these populations with those of nearby naturally occurring substrates and their surrounding sediments. After 2 yr, 239 foraminifera were found attached to 4 Seafloor Epibenthic Attachment Cubes (SEA3s). Dominant taxa included Cibicidoides wuellerstorfi var. lobatulus, Pyrgoella sp., and arborescent foraminifera. Variations in colonization height and abundance between plastic types were observed, but no clear drivers of these patterns can be ascertained from this study. Foraminiferal populations from elevated substrates and the nearby sediment cores showed no significant overlap in populations, suggesting that foraminifera colonizing SEA3s did not originate from surrounding sediments and likely recruited from other elevated substrates common in the area (e.g. glass sponges). This study demonstrates that plastics serve as hard substrates which deep-sea foraminifera inhabit and that plastics may persist for extended periods of time, potentially altering ecosystem compositions in environments dominated by soft sediments. There is a significant difference between colonizing epifaunal and sediment populations, which raises interesting questions about colonization and distribution processes in deep bathyal and abyssal environments. Epibenthic foraminifera attached to elevated substrates may be underrepresented in the sedimentary record through preservation and sampling biases.