Velocity and Sediment Disturbance of Periphyton in Headwater Streams: Biomass and Metabolism

Disturbance by floods is believed to be 1 of the fundamental controllers of temporal and spatial patterns in stream periphyton. However, the exact causes of biomass losses are still poorly understood and discharge measures of disturbance often only explain limited variance in periphyton development. We investigated the effects of 2 of the main mechanisms of flood disturbance to periphyton--frequency of high-velocity events and frequency of bed sediment movement--in an effort to better understand disturbance processes and improve the quantification of flood disturbance regimes for studies of stream periphyton. Three sites were selected in headwater streams in each of 4 groups according to a 2-way factorial design of frequency of high-velocity events and sediment stability, giving a total of 12 sites. Periphyton were sampled monthly for 15 mo and analyzed for chlorophyll a. Maximum photosynthetic rates (P max ), chlorophyll-specific P max , community respiration (CR), and P max :C...