Table 1. Screening effects of wire hardware cloth on periphyton primary productivity (mg C mp
4 h”). Comparison of productivity between screened and unscreened styrofoam substrates at two locations
in Lake Tahoe. The values represent the mean and standard deviation of five replicate sam))les at
each location for the indicated sampling period.
Productivity of periphyton (mg C nF) grown on Styrofoam substrates in Lake Tahoe.
A comparison of crayfish grazed vs. ungrazed
(caged) primary productivity (PPR) at each location.
Each point represents the mean of five
replicate samples. Brackets around the points of
the last two sampling periods represent I SD about
the mean.
Fig. 2. Productivity of periphyton (mg C mm2
h”) in laboratory aquaria under various crayfish
grazing pressures. Crayfish were added to each
aquarium after stability of primary productivity
( PPR ) was maintained by the controls ( ungrazcd )
for 2 weeks. Brackets around the control points
represent 1 SD about the mean of eight replicates.
The numbers to the extreme right of each curve
indicate the crayfish biomass (g m-‘) represented
by that curve
Fig. 3. Linear regression of the difference in
periphyton primary productivity in experimental
aquaria vs. grazing biomass of Pacifastacus leniusctcltLs.