Does elevation matter? Living foraminiferal distribution in a hyper tidal salt marsh (Canche Estuary, Northern France)

• Published in: Estuarine, coastal and shelf science coastal and shelf science, 2017-07, Vol.194, p.192-204
• Main Authors: Francescangeli, F., Bouchet, V.M.P., Trentesaux, A., Armynot du Chatelet, E.
• Format: Article
• Language: English
• Subjects: Benthic foraminifera; Canche Estuary; Earth Sciences; Elevation; Hyper tidal estuary; Living fauna; Oceanography; Salt marsh; Sciences of the Universe
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/j.ecss.2017.06.023

In the present study we investigate the ecology and distribution of living benthic foraminifera to test the effect of hyper tidal exposure and their suitability as sea level indicators. Within a salt marsh area along the Canche Estuary (northern France), four transects were sampled to see the effects of maximal tidal constraints (shore transects) and minimal tidal constraints (alongshore transects). Multivariate analyses have been performed to determine the correlations between biotic (foraminiferal absolute abundances) and abiotic factors (elevation, grain-size, TOC and total sulphur). For each of the principal benthic foraminiferal species the tolerance to subaerial exposure have been estimated as well. Two distinctive foraminiferal zones have been identified along the vertical tidal gradient: a zone I in the higher part of the salt marsh dominated by agglutinated and porcelaneous taxa, and a zone II in the lower one dominated by hyaline specimens. Hyper tidal exposure constraints the foraminiferal vertical zonation in accordance with the tidal frame. However it does not constitute a threshold parameter able by itself to explain all the faunal variations in the Canche Estuary. For sea level indicators, foraminifera should be considered relative to tidal subaerial exposure rather than to absolute altitude. •Ecology of living benthic foraminifera are investigated in a hyper tidal estuary.•A high/middle marsh assemblage can be distinct from a lower one.•Hyper tidal exposure constraints the foraminiferal vertical zonation.•Tidal exposure is not the single parameter influencing foraminiferal distribution.•Living fauna is biased when used to monitor sea level in hyper tidal areas.