The effects of chlordane on the green algae Scenedesmus quadricauda and Chlamydomonas sp.

Abstract

Chlordane is an organochlorine soil insecticide whose effects upon aquatic ecosystems, and particularly on algae, are little known. Experimental results indicate that chlordane concentrations ranging from 0.1 to 100 μg/ℓ significantly stimulate cell division of Scenedesmus quadricauda, a common planktonic green alga. Chlordane in concentrations from 0.1 to 50 μg/ℓ is also stimulatory to the growth of Chlamydomonas sp., isolated from soil. However, 100 μg/ℓ was inhibitory to cell division in this species.Significant stimulatory effects on the respiration rates of these two species were observed at all concentrations within 3 to 4 h of chlordane addition. Stimulation of respiration increased with increasing chlordane concentration. Similar stimulatory effects on respiration were produced using 2,4-dinitrophenol (DNP), a known uncoupling agent of oxidative phosphorylation. Long-term inhibition of photosynthetic response of Scenedesmus quadricauda treated with the higher chlordane concentrations was observed over the course of the experiment even though a significant increase in cell numbers over the control was noted. A highly significant chlordane–light interaction was observed on photosynthesis of both S. quadricauda and Chlamydomonas sp.