Ecological considerations on phytoplankton from the Guajará bay and from the Guamá river estuary in Pará, Brazil

Abstract

Phytoplankton composition, biomass and ecology were studied from samples bimonthly collected from December/ 1989 to October/1990 at Guajará Bay-Pará (Brazil). Analysis was based on plankton samples collected with a 65 μm mesh net, horizontal-surface hauled. Biomass was calculated by Utermohl method (cell/liter) and chlorophyll ‘a’ concentration. Water salinity, temperature, transparence and pH were measured for composition. Phytoplankton was composed of 116 specific and infraspecific taxa: 1 Cyanophyceae, 45 Chlorophyceae and 70 Bacillariophyceae. Most significatives were Polymyxus coronalis, amazonic brackishwater indicator. Quantitatively phytoplankton varied from 790000 cel/l to 4790000 cel/l, being phytoflagellate the most abundant followed by diatoms, blue green and green algae. Chlorophyll ‘a’ varied from 1.49 mg/m3 to 23.33 mg/m3. Guajará Bay water is characterized by small salinity variation, high temperature, law transparence and pH generally acid. These parameters annual variation is related to pluviometer regime that influences the phytoplankton quantitative values.