PARENT SESSION
Oral Session #7: Aquatic Ecology: Stream ecosystems. Presiding: T. Ehlinger.
Monday, August 6, 2001. 8:00 AM to 12:00 PM. Hall of Ideas G.
The impact of lakes and small dams on benthic invertebrate distribution in streams.
Pollard, Amina1, Magnuson, John1, 1
ABSTRACT- Fragmentation due to the damming of rivers and streams can alter the distribution of benthic invertebrates, primarily because dams disrupt resource gradients. However, most studies have focused only on the effects of large dams on invertebrate distribution. Natural lakes and small impoundments (<100 ha) may also cause changes in flow regime. We ask whether the distribution of benthic invertebrates in a stream network is influenced by lentic disruptions of the stream caused by natural lakes and small dams. And if so, does the effect depend on the type of lentic disruption? Benthic invertebrate samples were taken along transects in inlet and outlet streams of natural lakes and impoundment in northern Wisconsin. We evaluate invertebrate community characteristics (abundance, richness and functional groups) to examine how the distribution is affected. Our comparisons of dissimilarity indicate that invertebrate assemblages in inlet streams are relatively homogenous compared to the assemblages in outlet streams. While this is the trend for both natural lake and impoundment systems, the differences are less evident in the streams associated with natural lakes. These preliminary analyses suggest that several types of lentic disruptions of streams influence invertebrate distribution but that the effect is greater in streams interrupted with small dams.
KEY WORDS: benthic invertebrate, stream, lake, dam