The study was conducted from October 2002 to October 2003.
According to the morphology of the lagoon and influence of covering
mangrove area (Twilley, 1988), calculated from mangrove
area: open water ratios (MA:OW), four zones were identified: high
influence zone (HIZ), low influence zone (LIZ), channel and rivers
(Fig. 1). Seven sampling stations were set up in the lagoon covering
these zones with one station in each of the 3 main rivers that drain
into the lagoon at a distance of approximately 100 m from the
mouth (Fig.1). Samples were obtained bimonthly fromeach station
at two depths: surface and 20 cm above the bottom (0.70 m the
shallowest station and 2.5 m the deepest except station 10 which
reached 15 m). The sampling design considered samples taken
from each station as replicates within each zone. All field sampling
was done between 09:00 and 14:00 h, sampling the stations in the
same order.