Variação espaço-temporal do fitoplâncton em um estuário amazônico.

Abstract

In order to determine the spatial and temporal variation of phytoplankton associated with environmental parameters fortnightly collections were made in the estuary of the river Guajará Mirim, during dry period (September/11, November/11, julho/12) and rainy (January/12, March/12, May/12), in ebb and flood tide in four collection points, and simultaneously two Diel samples were collected in the months of November/11 and March/12. For the qualitative and quantitative study of the phytoplankton plankton net of 64 μm and Kitahara bottle was used. Were measured in situ the parameters temperature, salinity, pH, dissolved oxygen; and water samples were collected for analysis of suspended solids, salts nutrients (nitrite, nitrate, n- ammonia, phosphate and silicate) and chlorophyll a. 165 taxa were identified especially diatoms (78 %), Chlorophyceae(14 %), cyanobacteria (4 %), dinoflagellates (3 %) and euglenoids (1 %). The seasonal phytoplankton density showed a significant difference, with maximum values in the less rainy period (92,200 cel.L-1, September/11), with a predominance of diatoms, with 94 % of the total density. Species diversity was low due to the dominance the species Coscinodiscus concinnus, Chaetoceros compressus and the Pseudanabaena sp least rainy season and Polymyxus coronalis and Aulacoseira granulata for the rainy season. The spatio- temporal variation (diurnal and tidal) had no influence on the environmental and biological parameters. The rainfall was the main forcing on seasonal variation highlighting the transition period (between the rainy and less rainy period), which was the main determinant in the distribution, density and concentration of phytoplankton biomass.