Sediment reworking of intertidal sediments by the benthic foraminifera Haynesina germanica : the importance of motion behaviour and densities

Abstract

This study aimed to describe for the first time the vertical motion behaviour of the intertidal foraminifera Haynesina germanica and its contribution to bioturbation. Its infaunal behaviour leads to the creation of a one-end tube within the first centimetre of sediment. In addition, a vertical trail following behaviour was described for the first time in foraminifera, which may be linked to the sustainability of the biogenic sedimentary structures. As a consequence, H. germanica produces a vertical transport of both mud and fine sediment fractions similarly to the sediment reworking mode reported for gallery-diffusor benthic species. This finding allows us to refine the bioturbating mode of H. germanica , previously classified as surficial biodiffusor. Furthermore, sediment reworking intensity appeared to be dependent on the foraminiferal density. H. germanica would adapt its motion behaviour to deal with the intra-specific competition for food and space that may occur when density increases. Consequently, this behavioural modification would affect both the species and the individual contribution to sediment reworking processes. In fine , sediment reworking in H. germanica may further contribute to the bioirrigation of intertidal sediments, which has implications for oxygen availability in sediments and on aerobic microbial processes involved in carbon and nutrient cycling at the sediment–water interface.

Single-celled bioturbators: benthic foraminifera mediate oxygen penetration and prokaryotic diversity in intertidal sediment

“…In our experiment, benthic foraminifera built up burrows down to 7 mm in the sediment. Although these burrows were not as deep as the centimetre-long burrows previously reported on miliolid and some deep-sea species (Severin et al, 1982;Groß, 2002;Heinz and Geslin, 2012), they were of the same order of magnitude as is known for the coastal species Ammonia beccarii (Green and Chandler, 1994) and the dominant species in our study Haynesina germanica (Deldicq et al, 2023). These shallow burrows confirm that the intertidal foraminiferal species used in the present experiment prefer oxygenated microhabitats (Bouchet et al, 2009;Cesbron et al, 2016).…”

“…In spite of their role in benthic ecosystem functioning (Moodley et al, 2000;Geslin et al, 2011), the role of foraminifera as bioturbators remains a fairly untapped question, with only a few pioneer studies looking at how their displacement may affect the sediment reworking process (Severin et al, 1982;Hemleben and Kitazato, 1995;Groß, 2000). Noticeably, their ability to move in the sediment column affects the surface sediment cohesiveness (Cedhagen et al, 2021) and contributes to the horizontal and vertical transport of sediment particles (Groß, 2002;Deldicq et al, 2020Deldicq et al, , 2021Deldicq et al, , 2023. Consequently, foraminifera are assumed to affect sediment porosity and allow for "good sediment ventilation" (Hemleben and Kitazato, 1995;Groß, 2002).…”

Single-celled bioturbators: benthic foraminifera mediate oxygen penetration and prokaryotic diversity in intertidal sediment

“…In spite of their role in benthic ecosystem functioning (Moodley et al, 2000;Geslin et al, 2011), the role of foraminifera as bioturbators remains a fairly untapped question, with only a few pioneer studies looking at how their displacements may affect sediment reworking process (Severin et al, 1982;Hemleben and Kitazato, 1995;Groß, 2000). Noticeably, their ability to move in the sediment column affects the surface sediment cohesiveness (Cedhagen et al, 2021) and contributes to the horizontal and vertical transport of sediment particles (Groß, 2002;Deldicq et al, 2020Deldicq et al, , 2021Deldicq et al, , 2023. Consequently, foraminifera are assumed to affect sediment porosity and allow for "good sediment ventilation" (Hemleben and Kitazato, 1995;Groß, 2002).…”