Patterns of metal accumulation by natural river biofilms during their growth and seasonal succession.

To evaluate the factors influencing patterns of metal accumulation by river biofilms, concentrations of chromium (Cr), nickel (Ni), copper (Cu), and lead (Pb) in biofilms from Erh-Jen River and San-Yeh-Kung Creek were investigated during their growth and seasonal succession. Different metal-accumulation patterns during biofilm development were observed between the two rivers. Mature biofilms (grown for 21-28 days) in both rivers showed maximum metal accumulation (≤3.24 × 10(4), 1.55 × 10(4), 7.40 × 10(3), and 7.80 × 10(2) μg g(-1) of Cr, Ni, Cu, and Pb, respectively) and bioconcentration factors (≤7.15 × 10(5), 1.60 × 10(5), 2.60 × 10(5), and 4.22 × 10(5) l kg(-1) of Cr, Ni, Cu, and Pb, respectively). These types of biofilms had the characteristics of being good metal accumulators and the ability to integrate metal-exposure conditions, suggesting that they were suitable biomonitors for metal-contaminated water. Seasonal succession in metal-accumulation ability of 1-month-old biofilms from Erh-Jen River was mainly affected by changes in bacterial and algal biomass and chemical oxygen demand in water, whereas that from San-Yeh-Kung Creek was primary influenced by concentrations of total nitrogen in water. Synergistic interaction between these four metals on metal-binding sites within biofilms was also shown.