Intra- and inter-specific variability in benthic foraminifera modulates surface sediment reworking

Abstract

Bioturbation is a key ecological process that regulates benthic ecosystem functioning, including organic matter remineralization and nutrient regeneration. Despite growing evidence that meiofauna, and benthic foraminifera in particular, contribute to sediment bioturbation, the extent to which bioturbation modes and rates vary within and among meiobenthic species remains insufficiently understood. In this context, using three-dimensional microtopographic mapping, the present study investigates both inter- and intra-specific variability in the surface sediment reworking rate (SSRR) generated by four common intertidal benthic foraminiferal taxa, with different biological traits (e.g. shape, microhabitat). Inter-specific variability was examined by comparing the SSRR of three similarly sized taxa differing in morphology, namely Ammonia confertitesta, Haynesina germanica and Quinqueloculina spp. By contrast, intra-specific variability was assessed using Quinqueloculina spp. individuals distributed across five size classes ranging from 200 to 700 µm. Furthermore, the interplay between size and biological trait was investigated by including an additional species, Eggerelloides scaber. Our results demonstrate that SSRR increases markedly with individual size (e.g. SSRR generated by Quinqueloculina spp. increases from 0.59 to 20.56 mm³ ind⁻¹ d⁻¹ between the smallest and highest group size) and that species of comparable size can produce highly contrasting reworking patterns depending on their biological traits.