Unanticipated
changes in freshwater ecosystems
are often due to alterations
in the complex connections among
sediment-dwelling species and associated
food webs (e.g., Goedkoop
and Johnson 1996, Lodge et al.
1998b, Stockley et al. 1998) or to
disturbances, such as floods or
drought (e.g., Covich 1993, Power
1995, Johnson et al. 1998), that alter
the species composition of the
benthos. In addition, benthic species
can themselves constitute a distur