Effects of the sandbar breaching on hydrobiological parameters and zooplankton communities in the Senegal River Estuary (West Africa)

Abstract

This study describes the changes in hydrology, zooplankton communities and abundance in the Senegal River Estuary (SRE) before and after the breaching of the sandbar in October 2003. Samples were taken in 2003 at 3 stations located upstream (DI), in mid estuary (HY) and downstream (RM), and in 2005 at the same stations (RM becoming Old River Mouth: ORM), plus the new river mouth (NRM) resulting from the morphological evolution of the SRE.The study showed marked seasonal variations that affected the structure and distribution of zooplankton as well as major changes caused by the sandbar opening:–increased marine influence throughout the whole SRE,–changes in the horizontal gradients,–arrival of euryhaline species and increase in meroplankton, in particular decapod larvae,–transformation of the ORM area into a slackwater area with limited exchanges and the highest zooplankton numbers during high waters.