Structural equation model
The structural equation model indicates that both shading and snails
affect primary producer biomass (Figure4). Shading and snail herbivory
both negatively affected biomass of P. crispus (standardized path
coefficient, SPC = −0.61 and −0.25 respectively). Snail herbivory
decreased (SPC = −0.56), and shading increased (SPC = 0.32) biomass of
periphyton (r 2 = 0.29). Both shading (SPC =
0.35) and snail (SPC = 0.36) significantly increased the biomass of
phytoplankton (r 2 = 0.49).