THE ULTRASTRUCTURAL RESPONSE OF 2 MORPHOLOGICALLY DISTINCT FORMS OF CLADOPHORA-GLOMERATA TO THE ALGICIDE HYAMINE

Two morphologically distinct forms of Cladophora glomerata isolated from the eastern Great Lakes, one from summer and the other from fall, were used in bioassays in a toxicity test of the algicide Hyamine. Ultrastructurally, the two forms exhibited variations in outline of the cross section, cell wall, chloroplasts, thylakoidal membrane arrangements, and abundance of starch and lipid bodies. The summer form which predominated over other submerged filamentous algae in creeks and riverbeds and along lake shorelines was found to be more tolerant of the algicide, showing only apical cell damage al a concentration of 0.5 mg/L after 4 days. In contrast, the fall form prevailing in late November was completely destroyed at this concentration. The impact of the possible existence of more than one genetic form of C. glomerata in the Great Lakes is discussed in view of this species' frequent use in biomonitoring and bioaccumulation studies.