Primary production and pigments in three low alkalinity connected reservoirs receiving mine wastes

Abstract

A comparative study of primary production and pigments, conducted from April 1981 to April 1982, in a chain of three low alkalinity reservoirs situated in north of Portugal revealed significant lower values (159 mg C m-2 d -1 and 19.8 mg m -2 as chlorophyll a, growing season means) in the reservoir receiving wastes rich in copper from a tungsten copper pyrite mine. This contrasts specially with the situation observed in the upstream reservoir which presents the highest values (409 mg C m -2 d -' and 55 .2 mg m -2) recorded in the system . Eventual effects of the mine discharge on phytoplankton biomass and photosynthesis such as high turbidity and copper toxicity are discussed . Results point out to be the presence of copper responsible for the alterations in the phytoplankton community . The system exhibits similar photosynthetic capacity which indicates an adaption to the relatively high copper concentrations in water and sediments .Experiments carried out in the largest unpolluted reservoir show that the loss of carbon through respiration is of major importance and indicate the phosphorus to be one of the factors limiting phytoplankton productivity. 173

Cultural eutrophication of West Point Lake ? a 10-year study

“…Ratios for West Point Lake ranged from low of 0.2 during the cool season of 1976 to a high of 4.9 during the warm season of 1984 (Table 3). As expected, cool season ratios were generally lower than warm season ratios (Fogg, 1965;Cabecadas & Brogueira, 1987). However, in 1985 the unusually high warm season chlorophyll concentrations (Table 3) resulted in a photosynthetic efficiency lower than the cool season for that year.…”