Effects of snail herbivory
Shading and snail herbivory interactively affected the growth ofP. crispus . Under full light conditions, low biomass of snails
promoted the growth of P. crispus , while during high biomass of
snails the macrophyte growth was inhibited. This may be a consequence of
preferential feeding of snails on periphyton over macrophytes
(Bronmark, 1989;
Guo et al., 2021;
Koleszár et al., 2021;
Zhi et al., 2020). During low biomass of
snails there is plenty of periphyton available to graze, and herbivory
in this case releases macrophytes from competitive pressure for light
with periphyton, promoting the growth of macrophytes
(Yang et al., 2020). In contrast, during
high biomass of snails, periphyton food is depleted and snails will
graze on macrophytes, thus inhibiting their growth
(Zhi et al., 2020). However, during
shaded conditions, the preferential food availability to snails is
limited at a high grazing pressure, forcing snails to graze on
macrophytes.