The influence of flow and other environmental factors on benthic invertebrates in the Sacramento River, U.S.A.

We examined how community composition of benthic invertebrates was related to current velocities and other environmental variables within the Sacramento River in California, USA. Invertebrates were collected in 1998 and 1999 from 10 sites over a gradient of 187 river kilometers. Canonical correspondence analysis revealed that current velocity was the most important variable explaining community composition. Other predicator variables that influenced community composition included periphyton biomass, altitude, and disturbance. Because of the importance of velocity in structuring benthic communities in this system, alterations of flow caused by changes in river regulation structures should be carefully considered.