The sensitivity of two Monoraphidium species to zinc: their possible future role in bioremediation

Effects of zinc on growth, cell morphology, oxidative stress responses and zinc removal activity of two common phytoplankton species, Monoraphidium pusillum (Printz) Komárková-Legnerová and Monoraphidium griffithii (Berkeley) Komárková-Legnerová were investigated at a concentration range of 0.2–160 mg l^-1 zinc. Cell densities and chlorophyll content decreased compared with controls in cultures of both species, effective concentrations causing 50 % growth inhibition within 72 h on the basis of cell numbers were 33.69 and 25.63 mg l^-1 zinc for M. pusillum and M. griffithii, respectively. Changes in cell morphology and elevated lipid peroxidation levels appeared in zinc-treated cultures of both species, but only at higher (>10 mg l^-1) zinc concentrations. The most effective zinc removal appeared at 20 and 10 mg l^-1 zinc concentration for M. pusillum and M. griffithii, respectively. Removed zinc is mainly bound on the cell surface in the case of both species. This study provides new data for the zinc tolerance and zinc removal ability of the green algae M. pusillum and M. griffithii and shows that green algal species common in surface waters could have zinc tolerance and zinc-binding abilities, which makes them feasible in treatment of waters contaminated with 10–20 mg l^-1 zinc.

Keywords
Common green algal species; Zinc; Growth inhibitions; Morphological changes; Lipid peroxidation; Removal