Local environmental drivers override cascade effects on phytoplankton and periphyton along a dammed river continuum
Abstract
River damming alters hydrology, light availability and nutrient dynamics, thereby reshaping both pelagic and benthic primary producers. In double-dam systems, it remains unclear whether the two structures function as a single unit (“double-dam effect”) or whether the downstream dam adds cumulative impacts (“cascade effect”). Over two hydrological years, we investigated the responses of phytoplankton and periphyton to cascading dams, along the Sélune River (France), focusing on photosynthetic activity, biomass and assemblage. Using multivariate analyses, we quantified the relative influence of local environmental and climatic conditions (light, temperature, turbidity, nutrient concentrations and stoichiometry, conductivity, pH, dissolved oxygen, rainfall), spatial position along the river continuum, habitat type (lotic vs. lentic), and season on both communities. Local environmental factors explained most of variance in phytoplankton and periphyton, with light availability, temperature, and nutrient stoichiometry (TDN:TDP) as the dominant drivers. By explicitly testing cascade versus double-dam effects through comparisons of biological variables (activity, biomass and species abundances) between dams and with the downstream lotic station, we found evidence for a single-dam effect for both phytoplankton and periphyton. This pattern likely reflects short water residence times, which constrain the development of cumulative impacts along the dam cascade.
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BibTeX
@article{pannard2026local,
title = {{Local environmental drivers override cascade effects on phytoplankton and periphyton along a dammed river continuum}},
author = {Alexandrine Pannard and Caroline Gorzerino and Marion Chorin and Guillaume Bouger and Ophélie Fovet and Stéphanie Massé and Jean-Marc Roussel and Danièle Vassaux and Christophe Piscart},
journal = {Inland Waters},
year = {2026},
month = oct,
doi = {10.1080/20442041.2026.2644320},
url = {https://hal.science/hal-05574658v1},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Local environmental drivers override cascade effects on phytoplankton and periphyton along a dammed river continuum
AU - Alexandrine Pannard
AU - Caroline Gorzerino
AU - Marion Chorin
AU - Guillaume Bouger
AU - Ophélie Fovet
AU - Stéphanie Massé
AU - Jean-Marc Roussel
AU - Danièle Vassaux
AU - Christophe Piscart
PY - 2026
DA - 2026/10/08
JO - Inland Waters
DO - 10.1080/20442041.2026.2644320
UR - https://hal.science/hal-05574658v1
AB - River damming alters hydrology, light availability and nutrient dynamics, thereby reshaping both pelagic and benthic primary producers. In double-dam systems, it remains unclear whether the two structures function as a single unit (“double-dam effect”) or whether the downstream dam adds cumulative impacts (“cascade effect”). Over two hydrological years, we investigated the responses of phytoplankton and periphyton to cascading dams, along the Sélune River (France), focusing on photosynthetic activity, biomass and assemblage. Using multivariate analyses, we quantified the relative influence of local environmental and climatic conditions (light, temperature, turbidity, nutrient concentrations and stoichiometry, conductivity, pH, dissolved oxygen, rainfall), spatial position along the river continuum, habitat type (lotic vs. lentic), and season on both communities. Local environmental factors explained most of variance in phytoplankton and periphyton, with light availability, temperature, and nutrient stoichiometry (TDN:TDP) as the dominant drivers. By explicitly testing cascade versus double-dam effects through comparisons of biological variables (activity, biomass and species abundances) between dams and with the downstream lotic station, we found evidence for a single-dam effect for both phytoplankton and periphyton. This pattern likely reflects short water residence times, which constrain the development of cumulative impacts along the dam cascade.
SN - 2044-2041
SN - 2044-205X
ER -