The Hg accumulation in N. closterium
was higher than in Chlorella sp. This was probably due to the bigger
cell volume of N. closterium. Besides, some studies suggested that
the higher surface adsorption of copper in Scenedesmus vacuolatus
than in Chlorella kessleri was attributed to higher copper-binding
capacity of S. vacuolatus wall glucomannans, compared to poly Nacetylglucosamine
present in C. kessleri’s wall (Prasad et al., 1998;
Schiariti et al., 2004). Thus, the differences in cellular wall
composition of Chlorella sp. and N. closterium may be partly
responsible for their differences on MeHg affinities.