Periphyton dynamics in a floodprone prealpine river: evaluation of significant processes by modelling

Abstract

1. Periphyton chlorophyll a was measured at weekly or 2 weekly intervals from October 1992 to March 1994 at four sites in a Swiss prealpine gravel bed river that was frequently disturbed by unpredictable spates. 2. To evaluate the dominant processes that control periphyton biomass, measured data were compared with a set of simulations from an empirical dynamic periphyton model. Different combinations of process hypotheses were systematically activated and deactivated in order to assess their importance. 3. The simplest model leading to an acceptable agreement with measured data employs a biomass‐dependent growth rate, a detachment rate directly proportional to discharge and biomass, and a catastrophic loss rate during bed moving spates. Terms describing light or temperature dependence had a minor effect on the model fit. 4. The model describes the temporal pattern of the periphyton biomass as a series of growth curves periodically truncated by spates. Within the uncertainties of the measurements, mainly caused by the spatial heterogeneity of periphyton, the biomass recovered along deterministic trajectories. 5. Sensitivity analyses with respect to model parameters and model structure showed that site‐specific model parameters could not be unequivocally determined, and that the model yields similar results with slightly different formulations of processes. This indicates that the data base with respect to periphyton biomass was too small for a unique identification of model details but that the main conclusions on the significance of processes did not depend on arbitrary choices of the model formulation.

Environmental control of seasonal and inter-annual variations of periphytic biomass in a North Iberian stream

“…Spates are disturbances that slough and reset algal biomass to low values, and periphytic communities can recover more or less, depending on the length of periods between floods and on the light and nutrient levels available during these periods (Elósegui & Pozo 1998). In torrential systems, periphytic biomass can exhibit large inter-annual variations as a result of differences in rainfall patterns (Uehlinger et al 1996, Uehlinger 2000. Therefore, in order to compare periphyton abundance between streams, it is essential to have an idea of interannual variability in discharge, and of its effects on periphyton.…”

The succession dynamics of a macroalgal community after a flood disturbance in a tropical stream from São Paulo State, southeastern Brazil

“…However, the organisms that inhabit in running waters need mechanisms to avoid or resist mechanical stress caused by water flow (Gordon et al 1992). Thus, several authors have suggested that the disturbance produced by current velocity is very important to the settlement and maintenance of the periphytic biomass in lotic ecosystems (Horner & Welch 1981, Steinman & McIntire 1986, Lamberti et al 1991, Uehlinger et al 1996.…”

“…According to Lake (2000), flow disturbances can destroy preexisting habitats and create new ones that will be colonized and inhabited by a new biota, after the return of stability in flow conditions. Uehlinger et al (1996) believe, in these circumstances, that the recovery of algal communities is dependent upon re-growth of persistent plant and to the establishment of those considered recolonizers.…”

Nonlinear Relationship of Near-Bed Velocity and Growth of Riverbed Periphyton

“…Uehlinger et al [31] evaluated the dominant processes controlling periphyton biomass by comparing chlorophyll a (Chl-a) estimates with simulated outputs from an empirical dynamic periphyton model. Uehlinger et al [13] used a hyper-model considering the dependencies of periphyton growth and detachment on internal and external variables, such as incident light, water temperature, biomass, and discharge.…”

“…Uehlinger et al [13] used a hyper-model considering the dependencies of periphyton growth and detachment on internal and external variables, such as incident light, water temperature, biomass, and discharge. Graba et al [16] used a simplified form of the model introduced by Uehlinger et al [31] and determined that the role of local hydrodynamics in the catastrophic detachment process is likely associated with the magnitude of floods. Recently, response surface methodology (RSM) has attracted significant attention as a statistical tool to determine the optimal conditions for multiple variables [32][33][34].…”