ABSTRACT
The contribution of benthic foraminifera to sediment
bioturbation has widely been overlooked despite their huge abundance in
intertidal soft sediments. In this preliminary study, we specifically chose to
focus on two key species of benthic foraminifera in temperate intertidal
mudflats, Quinqueloculina seminula and Ammonia tepida, and
first experimentally investigated their individual movements at the sediment
surface. We subsequently derived from these observations the individual-level
surface sediment reworking rates, and used the actual abundance of these
species to extrapolate these rates at the population level. Individual surface
sediment reworking rates SSRRi ranged between 0.13 and 0.32 cm2·ind-1·day-1 for Q. seminula, and between 0.12 and 0.28 cm2·ind-1·day-1 for A. tepida. Population-level surface sediment reworking rates were
subsequently estimated as ranging between 11,484 and 28,710 cm2·m-2·day-1 for Q. seminula and 27,876 and 65,044 cm2·m-2·day-1 for A. tepida. Noticeably, these reworking rates are comparable to, and
eventually even higher than, the rates reported in the literature for
populations of intertidal macro-invertebrates, such as the annelid polychaete Melinna
palmata and the bivalve Abra ovata. Taken together these
results suggest that despite their minute size intertidal benthic foraminifera
are, thanks to their abundance, non-negligible contributors to the reworking of
surface sediment, and may then play an unanticipated role in the benthic
ecosystem functioning, through e.g. the enhancement of fluxes at the
sediment-water interface.