EFFECTS OF YOUNG COMMON CARP (CYPRINUS CARPIO L.) ON SESTON DYNAMICS IN EXPERIMENTAL CULTURESidorkewicj, N.S. Freije, H. and Lopez Cazorla, A.C.Abstract The effect of one-year-old common carp (Cyprinus carpi° L.) on seston biomass, chlorophyll a concentration, water turbidity and light extinction was studied in 100- I glass aquaria. Two 30-day experiments were conducted using a muddy sediment or a pebbly bottom. In both cases, three treatments based on different fish size (two fish/ aquarium) were assayed. Aquaria with no fish were used as controls. Under conditions of muddy bottom, an increase in chlorophyll concentration was recorded from the beginning to the end of the experiment. Seston biomass, turbidity and light extinction increased significantly during the first week but subsequently decreased. Significant differences between treatments were observed for each of the studied variables. Higher concentrations of chlorophyll were obtained when the bottom was pebbly (final values 31-74 .1,g 1.1) than when it was muddy (18-33 ugl-'). However, the reverse was true for the other parameters which had a high variability over time and did not show major differences between fish-size treatments. Light attenuation (maximum extinction coefficients 19 and 3 in-' in muddy and pebbly conditions, respectively) was mainly determined by inorganic tripton in muddy bottom, whereas in.the pebbly condition both abiogenic fractions contributed almost equally to light extincton. Our results will hope fully help to clarify the effects of carp on the water quality of an irrigation system of Argentina. where this exotic fish is present.
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