SS3.13 Natural Disturbances on Landscapes and Their Impacts on Aquatic Systems
Date: Thursday, June 13, 2002
Time: 5:00:00 PM
Location: Carson A
 
MooreJW, University of Washington, Seattle , USA, jwmoore@u.washington.edu
Schindler, D, E, University of Washington, Seattle, USA, deschind@u.washington.edu
Scheuerell, M, D, University of Washington, Seattle, USA, scheuerl@u.washington.edu
 
THE IMPACT OF SOCKEYE SALMON NEST DIGGING ON STREAM AND LAKE BENTHIC COMMUNITIES
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Salmon nest digging is a spatially and temporally predictable disturbance of aquatic benthic systems. Spawning sockeye salmon dig nests about 2 m2 in area and 20 cm deep in stream and lake substrates. The importance of this physical disturbance is unknown. We excluded sockeye from spawning areas in two streams and two lakes in southwestern Alaska to characterize the effects of sockeye spawning on benthic communities. Sockeye exclosures allowed the flow of small biota and particles and did not measurably differ from the exclosure controls in how they altered water currents. Before salmon arrived, exclosure and control sites did not differ in substrate composition, or invertebrate and algae densities. However, during sockeye spawning, there were decreased densities of invertebrates, algae, and fine sediment in areas with spawning sockeye relative to exclosures. These results demonstrate that salmon spawning can dramatically impact the biota and physically modify aquatic environments. As salmon populations decline, streams and lakes are losing not only an important nutrient subsidy, but also an ecological engineer and source of benthic disturbance.