Abstract
Tadpole impact on periphytic algae was estimated with an exclosure experiment in the field. Algae growth on control (exposed) and experimental (netted-in) Perspex plates was measured in 12 ponds in 1991 and 8 in 1993.An index of snail (Lymnea and Planorbis)presence in the ponds was used to correct their effect. Grazing pressure (difference in amount of algae between control and experimental plates)differed between ponds. The difference was correlated to amount of Rana tadpoles present in the pond. At the higher densities of tadpoles observed in the study ponds, the algae standing crop on exposed plates was about 50–75% of that on netted-in plates. These result demonstrate that there is potential for effects of exploitation competition in ponds with a high tadpole density.
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