Hydrography and phytoplankton biomass and abundance of North-East Brazilian waters

The spatial variability of oceanographic characteristics as well as the int errelationship between production levels and environment al characteristics in NE-Brazilian waters during the JOPS-II 5 expedition were investigated. Sixty-seven stations along 14 transects off major mangrove systems were sur veyed. CTD profiles (0 to 400 m) and water samples (at 0, 50, 100, 150, 200 m depth) were used for determining phytoplankton density, chlorophyll a, d issolved oxygen and nutrients (NO2, NO3, PO4 and SiO4). Although the differ ences in water properties were not very pronounced between the stations, th ree oceanographic regions could be distinguished from the surface waters: O ceanic waters from Fortaleza to Cabo Calcanhar; oceanic waters from Natal t o Tamandare and shelf waters. At the top of the thermocline, waters to the north of Macau were distinct from those to the south of Cabo Calcanhar. Whi le the nutrient levels and phytoplankton biomass were very low over the who le area, they were higher towards the innershelf. Mangrove export, via rive r discharge and shelf break upwelling could be the mechanisms contributing to the productivity of NE-Brazilian waters.