Ref ID : 1644
Timo Kairesalo and Irma Koskimies; Grazing by oligochaetes and snails on epiphytes. Freshwater Biology 17:317-324, 1987
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1. The isotope [33]P was used to assess the effect of grazing by oligochaetes (mainly Stylaria lacustris L.) and the snail, Lymnaea peregra (Muller), on epiphytes within an Equisetum fluviatile L. stand. 2. Two 1 m2 polystyrene enclosures were set up within the emergent macrophyte zone of the lake. At the start of the experiment [33]P-solution was mixed with the water in both tanks. Algal and animal samples for [33]P-analysis were collected during the peak occurrence of epiphytes in June. 3. Phosphorus release rates from the animals through defaecation and excretion were measured in the laboratory. The grazing rate of oligochaetes was 2.2-4.1 mgP m-2 (of bottom) day-1 of which about two-thirds was released and recycled. The oligochaete density ranged from 13,400 to 20,900 m-2. The snails (25 ind.m-2) grazed 1.2-1.5 mgP m-2 day-1 of which about a quarter was released through defaecation and excretion. 4. Daily consumption by the oligochaetes and snails corresponded to 22-45% of the average phosphorus uptake by the epiphytes.