Zinc is essential micronutrient for organisms; however Zn at high level can be toxic. Environmental pollution by zinc is frequently related to mining activities, electroplating, metallurgy, domestic and industrial sewage. Phosphorus is critical to the support of life organisms and excess phosphorus from home domestic sewage and fertilizers from agriculture land can cause eutrophication. Aquatic ecosystems are rarely disturbed by a single type of stressor. Metal pollution is frequently associated with eutrophic condition. To better understand the impact of toxic metals in water bodies with varying nutrient conditions is necessary to elucidate the interaction between metal and nutrients with respect to their effect on biota. The aim of the study will be evaluated the effect of phosphate on zinc toxicity to the algae Raphidocelis subcapitata. R. subcapitata will be maintained in the LC Oligo medium that does not contain ethylene diaminitetracetic acid. Phosphorus will be furnished in the three concentrations: 3x10-4 mol L-1 (recommended in L.C. Oligo medium), 2.3×10-6 mol L1 e 6×10-7 mol L1. These phosphorus concentrations represent replete and limited concentrations in aquatic ecosystems that are environmentally relevant. That acclimation will be necessary to the algal reflect the actual nutrient available in the medium. After acclimation, algal cells will be inoculated into medium containing different zinc concentrations (0,15x10-6 mol L-1 a 2,45x10-6 mol L-1 Zn). Algal growth in the toxicity tests will be monitored through cell counts. The zinc concentration that inhibited 50% of the algal population will be calculated at different phosphorus concentration.
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