HR: 1330h
AN: B33E-26    [Abstracts]
TI: Influence of Carbonate Crusts on Trophic Cascades in Big Sur Streams.
AU: * Rundio, D
EM: dave.rundio@noaa.gov
AF: NOAA Fisheries, 110 Shaffer Road, Santa Cruz, CA 95060 United States
AU: Lindley, S
EM: steve.lindley@noaa.gov
AF: NOAA Fisheries, 110 Shaffer Road, Santa Cruz, CA 95060 United States
AB: Top-down effects of fish predation in streams are influenced by habitat conditions and traits of intermediate consumers. Along the Big Sur coast, seasonal carbonate crusts form in many streams, and appear to alter insect communities. We conducted a small-scale field experiment in two adjacent tributaries (crusted and crust-free) to determine the effects of predation by juvenile steelhead (Oncorhynchus mykiss) on invertebrates and algae in these different stream types. We hypothesized that a trophic cascade would be more likely in the crusted stream, which was dominated by an herbivore vulnerable to steelhead predation (Baetis), than in the crust-free stream, which was dominated by a less vulnerable herbivore (Agapetus). However, excluding steelhead from paving bricks had no effect on algae or Baetis in the crusted stream. Algal abundance was low, suggesting possible bottom-up control. In the crust-free stream, steelhead predation did not affect Agapetus, but nevertheless produced a trophic cascade by causing Baetis to increase by 85%, which in turn depressed algae by 25%. These results suggest that trophic interactions may differ between crust forming and non-crust forming streams, which we plan to test with additional sampling and experiments replicated across stream types.
DE: 9810 New fields (not classifiable under other headings)
SC: Biogeosciences [B]
MN: 2005 Joint Assembly