The second zone comprises the areas from the lower falls
to the estuary. This area is still under the tide influence and is
characterized by quiet waters and a muddy substrate. Riparian
vegetation often consists in the Aracea Montrichardia
arborescens. Hypostomus plecostomus occupies this area.
The third zone corresponds to the estuarial and littoral
area. This area is characterized by the direct influence of the
sea with different levels of salinity. Hypostomus watwata is
the only Guianese species of Hypostomus that is a permanent
resident of this zone.