Life on Plastics: Deep-Sea Foraminiferal Colonization Patterns and Reproductive Morphology

Plastic debris has become a persistent feature of deep-sea ecosystems, yet its role as a habitat for calcifying organisms remains poorly understood. Foraminifera colonization has been observed in significant numbers on plastic surfaces, suggesting that these materials serve as novel and significant deep-sea colonization sites for these abundant calcifying organisms. This study uses deep-sea experimental plastic substrates to examine the colonization and reproductive morphology of the benthic foraminifera Lobatula wuellerstorfi across three locations: Station M (4000 m), Oregon OOI (575 m), and Southern Hydrate Ridge (774 m). A total of 482 individuals were analyzed for morphometric traits, including proloculus diameter, to investigate reproductive morphotypes. The Oregon samples displayed a clear bimodal proloculus size distribution, consistent with alternating reproductive strategies, while Station M populations exhibited a broader, less defined bimodal distribution skewed toward megalospheric forms. A weak but significant increase in proloculus diameter over deployment duration was observed at Station M, suggesting a possible influence of experiment duration and/or substrate maturity and environmental conditions. These findings demonstrate that plastics can serve as persistent colonization sites for deep-sea foraminifera, offering a unique experimental platform to investigate benthic population dynamics, ecological plasticity, and potential geochemical implications, as well as the broader impacts of foraminifera on deep-sea biodiversity and biogeochemical cycling.