[Filtering capacity of Anodonta woodiana and its feeding selectivity on phytoplankton]

Lake eutrophication associated with algal bloom has become a major environmental challenge in China. Filter feeding organisms, e.g., silver carp, bighead carp, and zebra mussel, have been widely used to manipulate water environment through their top-down effects. The bivalve Anodonta woodiana is widely distributed across China, and has been used for bio-manipulation of some water bodies. In situ experiments were performed in a bay of Lake Dianchi and its surrounding ponds to study the filtering capacity and the filter feeding rate of Anodonta woodiana in these aguatic habitats, and to determine the controlling factors. The results showed that there was a relationship between filtration rate and total suspended substances measured in laboratory during August and September 2001 when the water temperature was 20 +/- 2 degrees C, which was expressed as y = 4 380.41 e(- 0.0184x) (R2 = 0.621, P < 0.05) based on at least squares analyses. The filtration rate was strongly related to the body weight by measuring in laboratory over 24 hours during August 2001 when the water temperature was 20 +/- 2 C. At least squares analyses gave the equation y = 2 904.16 + 12 076.24e(-0.0034x) (R2 = 0.9825, P = < 0.05). A slight variation of filtration rate was found over 24 hours, which could be explained by the bivalves' adaptation to the experimental circumstances rather than the daily change of its filtration feeding. In general, the filtration capacity of natural Anodonta woodiana population in the water bodies was very limited, as a result of its small population size. No significant selective feeding on algae was found by contrasting the relative abundance of algae in the habitats and the guts of Anodonta woodiana. The feeding selectivity on algae was neither correlated with the size of algae, nor with the initial abundance of algae in water column.