Hydrology and phytoplankton community structure at Itamaracá-Pernambuco (Northeast Brazil)

Quali-quantitative studies and hydrologic parameters were carried out in the profiles 6 (Orange) and 7 (Catuama) during the Victor Hensen cruise, in accordance with the bilateral scientific cooperation agreement Brazil/Germany. Hydrologically a zone of thermic and saline stability characterizes the superficial layer. The nutrient concentrations were generally low on the surface and higher at levels surpassing 100m in depth. 102 taxa were identified including diatoms (49), dinoflagellates (49), bluegreen algae (3), and euglenophyceae (1). The diversity and evenness were high, surpassing the environmental equilibrium. The clustering of samples showed evidence of 2 main groups, one encompassing the stations 32 and 38, characterized predominantly by Oscillatoria erythraeum, and another encompassing the remaining stations, characterized by dinoflagellates and diatoms. The clustering of species involved 4 groups, the biggest being oceanic marine species (49 species) and coastal and eurihaline marine species (31 species). The phytoplankton density varied from 50,000 cell.l-1 to 590,000 cell.l-1, characterizing an oligotrophic environment.