Cadmium sorption and toxicity in autotrophic biofilms

• Published in: Canadian journal of fisheries and aquatic sciences 2000-03, Vol.57 (3), p.530-537
• Main Authors: Hill, W R, Bednarek, A T, Larsen, IL
• Format: Article
• Language: English
• Subjects: Achnanthes; Algae; Cymbella; Freshwater; Lyngbya; Navicula; Synedra
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/cjfas-57-3-530

Autotrophic biofilms (periphyton) accumulate substantial quantities of metals from contaminated water. In this study, the time course of biofilm cadmium sorption was measured, the effects of current, biomass, and light on short-term cadmium sorption by biofilms were examined, and the toxicity of cadmium to biofilm photosynthesis was tested. The time course of cadmium sorption appeared to be a linear function of time over the 48-h measurement period. Biofilms in current greater than or equal to 2 cm times s super(-1) sorbed three to five times more cadmium than biofilms in still water. Cadmium sorbed after 4 h was 75% greater in high-biomass biofilm (2.5 mg dry mass times cm super(-2)) than in low-biomass biofilm (0.5 mg dry mass times cm super(-2)), but only in moving water. Light enhanced the sorption of cadmium 40% in one biofilm type. Cadmium toxicity to photosynthesis was evident after 24 h in thin biofilms exposed to initial cadmium concentrations greater than or equal to 10 mu g times L super(-1); photosynthesis by thicker biofilms was not significantly impaired even at the highest concentration (100 mu g times L super(-1)). Variations in current, biofilm biomass, and light are likely to influence the movement of metals in flowing systems.