Machado, R.C.A.; Feitosa, F.A.N.; Koening, M.L.; Flores Montes, M.J.; Bastos, R.B., and Jales, M.C., 2014. Phytoplankton productivity and hydrology of Porto de Galinhas reef ecosystem (Pernambuco, Brazil).

Porto de Galinhas beach is located on the south coast of Pernambuco, Brazil, around 50 km from Recife, has sandstone fringing reefs, and has intense tourist activity. To contribute to the environmental water quality, the phytoplankton biomass and productivity were analyzed, as well as some hydrological parameters at three fixed collection points. Water samples were collected in 3 months of both dry and rainy seasons, from the water column surface, at three fixed points between the reef and the beach, at high and low tides and diurnal spring tides. Temperature ranged from 26°C to 31°C, salinity ranged from 33 to 37, the saturation index of dissolved oxygen ranged from 97.16% to 174.54%. Nitrite and phosphate were lower than 1 μmol L⁻¹, nitrate was <2.5 μmol L⁻¹, and silicate ranged from 5.01 to 37.12 μmol L⁻¹. Chlorophyll a ranged between 1.17 and 3.23 mg m⁻³, productivity ranged between 1.36 and 23.90 mg C m⁻³ h⁻¹, and the assimilation rate was between 0.93 and 8.62 mg C mg Chl a ⁻¹ h⁻¹. The environmental parameters oscillated more in relation to seasonality than regarding the different tide stages and spatiality. According to the principal component analysis, rainfall was the most important physical forcing mechanism for the studied system, presenting direct correlation with suspended particulate material and nitrite and inverse correlation with the saturation index of dissolved oxygen, temperature, and transparency. The reef ecosystem is still free from the anthropogenic eutrophication process. It ranged from oligotrophic (dry season) to eutrophic (rainy season), and in the rainy season, the Maracaípe River plume can change the environmental conditions in the system. Although the reef area is under strong anthropogenic pressure due to intense local tourist activity, this impact has not been perceptible in the pelagic environment.