Effect of Simazine on Photosynthesis and Growth of Filamentous Algae

Abstract

Simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] inhibited photosynthesis 50% at concentrations of 1.1 μM forSpirogyra jurgensii(Kutz), 3.0 μM forPithophora oedogonia(Mont.) Wittr., and 3.8 μM forCladophora glomerata(L.) Kutz. Photosynthesis ofAnkistrodesmus braunii(Brun.), a nonfilamentous species, was inhibited the same amount by 4.7 μM simazine. The filamentous algal species had significant reductions in growth but no other phytotoxic symptoms when exposed to 5 μM simazine at light intensities of 100 μE·m–2·s–1and below. Algicidal effects did occur at a light intensity of 400 μE·m–2·s–1and were most severe inSpirogyra.The relationship between light intensity and simazine toxicity indicates algicidal effectiveness on these filamentous algae will be limited in habitats where light is reduced by turbidity, depth, or self-shading.