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Communication at the NABS Annual meeting, Keystone, 2000
(106) RESPONSE OF STREAM EPILITHON AND HERBIVORES TO A LIGHT GRADIENT IN EXPERIMENTAL CHANNELS.
P.M. Kiffney. National Marine Fisheries Service, Northwest Fisheries Science Center, 2725 Montlake Blvd. East, Seattle, WA 98112
I hypothesized that light was the primary factor limiting epilithon and herbivores in headwater, coastal streams of the Malcolm Knapp Research Forest, Maple Ridge, British Columbia. To test this hypothesis, I used shade cloth to manipulate light levels in experimental channels. 12 channels were seeded with algae, bacteria, detritus, and insects via streamwater from Mayfly Creek, a relatively pristine coastal rainforest stream. In addition to insect herbivores that colonized channels, I added 5 tadpoles of the tailed frog (Ascaphus truei) to each channel. Each channel was randomly assigned one of 4 light treatments: PAR=1.4 µ mol m2- s1-; PAR=6.5 µ mol m2- s1-; PAR=14.0 µ mol m2- s1-; and PAR=162 µ mol m2- s1-. Orthocladiinae abundance increased up to the 14.0 µ mol m2- s1- treatment, but there was no further increase at the highest light level. Tailed frog growth rates and survival also suggested that these animals were light limited, as survival was 42% in the lowest light treatment and 100% in the highest light treatment. These data suggest strong bottom-up control of stream epilithic food webs.
Presented at 11:15 AM on Tuesday, May 30, 2000 in Food Webs and Communities II
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