Assessing behavioural traits of benthic foraminifera: implications for sediment mixing
Résumé
The assessment of behavioural traits of marine organisms is increasingly recognized as a key issue to understand their role in ecosystem processes, such as bioturbation and nutrient cycling. The movement ability of intertidal foraminifera suggest that they may have a role, yet to be quantified, in benthic-pelagic coupling through their movement on the sediment, at the sediment-water interface and within the sediment. In this context, we investigated the behavioural traits of 5 benthic foraminiferal species typical of European temperate mudflats under standardized trophic light and temperature conditions. Behavioural traits related to motion of Ammonia tepida, Haynesina germanica, Cribroelphidium williamsoni, Miliammina fusca and Quinqueloculina seminula species were assessed through their travelled distance, velocity, tortuosity of the path, position in the sediment and activity index. By analogy with macrofauna bioturbation functional groups, we describe the studied foraminifera as biodiffusors-species with 3 subgroups defined according to their vertical position in the sediment. C. williamsoni belongs to the epifaunal-biodiffusors group while A. tepida and H. germanica belongs to surficial-biodiffusors. Finally, the species Q. seminula and M. fusca are considered as gallery-biodiffusors species. Our results further suggest that features such as velocity, activity and tortuosity may mediate sediment-mixing intensity. Therefore, Q. seminula, H. germanica and C. williamsoni which are the most active species, would have larger effect than the less active A. tepida and M. fusca on particles reworking rates. Taken together, our results suggest that benthic foraminifera may play an underestimated role in bioturbation processes.
Domaines
Sciences de l'environnement
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