The richness of macrobenthic organisms in the estuary
of the Rio Cachoeira as estimated in this study (n = 71) is
higher than that found in the estuary of the Paraguaçu River
(n = 62) by Barros et al. (2008) and lower than that in
Camamu Bay (n = 115) recorded by Hatje et al. (2008),
both studies conducted in the state of Bahia, Brazil. For
marine benthic macrofauna, polychaetes are usually the
group with the highest relative abundance, followed by
molluscs and crustaceans (Oliver & Mackie 1996). This
pattern was not observed in this study, since there was a
predominance of richness and abundance of molluscs over
the other groups. The large number of microgastropods collected in the outer estuary (St6) explains, in part, the
dominance of molluscs.
In conclusion, salinity, sediment characteristics, and
dietary habits were important in the composition and
distribution of organisms in this estuary. This is the first
study of benthic ecology held in the Cachoeira River estuary
and one of the few conducted in the estuaries of the State of
Bahia. It is desirable to carry out studies on longer temporal
scales, as well as to gather more information on the
population ecology of commercially valuable species
exploited in the region.