Research Paper

Diatom assemblages colonizing floating photovoltaic floaters are distinct from those in benthic and pelagic compartments of gravel pit lakes

¹ Centre de Recherche sur la Biodiversité et l'Environnement (CRBE), Université de Toulouse, CNRS, IRD, Toulouse INP, Université Toulouse 3–Paul Sabatier (UT3), UMR 5300, Toulouse, France
² Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France

^* Corresponding author: regina-lucia.guimaraes-nobre@univ-tlse3.fr

Received: 6 November 2024
Accepted: 3 April 2025

Abstract

The development of novel renewable energy technologies, such as floating photovoltaics (FPVs), is expanding, but their environmental consequences remain understudied. FPVs physically alter freshwater ecosystems by limiting light and wind penetration at the lake surface, while providing new substrates for biofilm development, including diatoms. Diatoms are essential to primary production and carbon cycling in aquatic systems, however, the composition of diatom assemblages on FPV structures remains unexplored. This study aimed to characterise the diatom assemblages colonising FPV floaters and compare them with those in the pelagic and benthic compartments of gravel pit lakes. Results showed significantly lower taxonomic richness and diversity on FPV floaters, followed by pelagic assemblages, with the highest values observed in benthic habitats. Community composition also differed significantly between the three compartments. Community composition also differed significantly across all habitats, but its dominance was particularly pronounced on FPV floaters (72%), compared to 54% and 32% in the benthic and pelagic compartments, respectively. As a low-profile, disturbance-tolerant taxon, Achnanthidium may thrive in low-light conditions created by FPV shading. It can also serve as a good water quality indicator, while baseline studies are needed to assess whether its dominance on FPVs reflects positive conditions for gravel pit lakes. By creating novel artificial habitats in the pelagic zone, FPVs can modify the patterns of primary production and pelagic-benthic coupling that remain to be investigated.