First evaluation of the restoration of Braças Lagoon (Figueira da Foz - Portugal)
Silva, P. C. L. D.; Gonçalves, F.; Ribeiro, R.; Soares, A. M. V. M.
published: Dec 23, 1997
ArtNo. ESP141014101006, Price: 29.00 €
Due to natural and anthropogenic changes, Braças lagoon (Figueira da Foz-Portugal) dried during the summers of 1989 and 1991-1993. In order to enhance the water level (by increasing depth) and water quality (by reducing internal nutrient loading), the sediment of this lagoon was partially removed in 1993 (August to October). Afterwards, this lagoon was monitored during 13 months for water temperature, conductivity, oxygen, pH, nitrates, nitrites, ammonium, phosphorus, depth and transparency, phytoplankton (chlorophyll-a) and zooplankton, in two zones: the dredged (DZ) and the non-dredged (NDZ). Sediment removal induced resuspension of fine particles, giving rise to a decrease in transparency and an increase in the amount of inorganic nutrients. Thereafter, DZ showed lower nutrient concentrations than NDZ, mainly regarding to phosphorus and nitrogen. Chlorophyll-a concentration was significantly lower in DZ (annual mean = 0.33 mg/m3) than in NDZ (annual mean = 2.31 mg/m3). In November (1993), zooplankton populations (rotifers, copepods and cladocerans) were already inhabiting the DZ. Ceriodaphnia pulchella Sars collected in previous studies was not recorded; otherwise, additional species were recorded (Ceriodaphnia reticulata Jurine, Simocephalus vetulus O. F. Müller and Moina rectirostris Leydig). Macrophyte vegetation did not develop in the DZ during the studied period.