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

Two morphologically distinct forms of Cladophora glomerata isolated fr om the eastern Great Lakes, one from summer and the other from fall, w ere used in bioassays in a toxicity test of the algicide Hyamine. Ultr astructurally, the two forms exhibited variations in outline of the cr oss section, cell wall, chloroplasts, thylakoidal membrane arrangement s, and abundance of starch and lipid bodies. The summer form which pre dominated over other submerged filamentous algae in creeks and riverbe ds and along lake shorelines was found to be more tolerant of the algi cide, showing only apical cell damage al a concentration of 0.5 mg/L a fter 4 days. In contrast, the fall form prevailing in late November wa s completely destroyed at this concentration. The impact of the possib le existence of more than one genetic form of C. glomerata in the Grea t Lakes is discussed in view of this species' frequent use in biomonit oring and bioaccumulation studies.