Abstract: A simulation test was carried out in laboratory to study effects of cleaning dredged material on growth of two species of marine microalgae (Chlorella sp. and Nitzschia closterium) as affected by its particle size and concentration. Results show that after 8 days of incubation, the effect of the materials on growth of the two species of marine microalgae was very significant regardless of their concentration (P<0.01). In the case that the suspended cleaning dredged materials were in the same range of particle size, but varied in concentration in the range of 1- 7 g•L^-1, the effect of inhibiting growth of the microalgae intensified with the rising concentration. With the suspended cleaning dredged materials declining in particle size, the two species of marine microalgae showed a downward trend in cell density. The effect was the least when the material was in the range of >88-125 μm in particle size, and the greatest when the material in the range of 0-16μm in particle size. The suspended cleaning dredged materials inhibited the growth rates of the two species of marine microalgae significantly, delaying the appearance of the maximum specific growth rate. Two species of marine microalgae were different in sensitivity to the suspended cleaning dredged materials. Chlorella sp. was more sensitive, which may be attributed to their difference in cell structure, physiological property and ecological habit.

Key words: cleaning dredged materials, Nitzschia closterium, Chlorella sp., particle size, concentration, effect