Effect of pH on the bioacumulation rates of heavy metals in macroalgae Bostrychia calliptera (Rhodomelaceae, Ceramiales)

Abstract

One of the factors with a bigger influence on the chemical characteristics of metal in solution is the level of acidity. Solution pH affects the cell wall metal-binding sites and the metal ion chemistry in water. This study evaluated the effect of pH on the bioaccumulation capacity in the red algae B. calliptera (Rhodophyta, Rhodomelaceae) exposed to different pH ranges. Algae thalli were subjected to different concentrations of mercury (Hg) and Lead (Pb), at concentrations from 0.1 to 10 mg/L for Hg and from 0.1 to 15 mg/L for Pb, respectively, during the following exposure times: 0, 12, 24 and 96 hours for each ion. Metal concentrations were determined by atomic absorption spectrophotometry according to standard APHA methods. The highest accumulation rates were found when the algae were exposed to pH 8 (for both Hg and Pb), which is a level very close to that measured in the study area. The metal concentration in the algae increased linearly until 48 hrs, a time where a greater accumulation efficiency was evident. The present study allowed to identify the potential use of the alga B. calliptera as a bioindicator species for heavy metals in estuarine environments.