Abstract: With a view to evaluating the function of particulate organic detritus in the Donghu Lake ecosystem, the authors made a study on the morphological characteristics of the degradation products from predominant plankters in the Lake. Accordingly, 4 plankters, i. e., a cladoceran (Daphnia carinata ssp.) and three species of bluegreen algae (Aphanizomenon flos-aquae, Anabaena spiroides, and Microcystis aeruginosa) were chosen as material of this study. Specimens collected from the Lake were killed artificially and the processes of detritus formation were traced. The moment that bacteria begin to come into direct contact with the dead organisms is considered to be the initiation of detritus formation. Four to five stages are delineated for the afore-mentioned species. The results of the authors'observation, compatible with Golterman's concept of algal mineralization, provide basis for the recognition and quantification of particulate organic detritus in the Lake.