Feeding behaviour of Dreissena rostriformis bugensis: functional response and selective feeding in Lake Geneva

Diplôme Master Feeding behaviour of Dreissena rostriformis bugensis: functional response and selective feeding in Lake Geneva eng 2026-07-31 author Rebecchi Nina Marie Paola 936330 director Ibelings Bastiaan Willem 781963 Forel Communs (FOREL) director Boudet Salomé Ernestine 939734 Forel Communs (FOREL) Dreissena rostriformis bugensis, an invasive dreissenid that has rapidly expanded in Lake Geneva since its first detection in 2015, filters large volumes of water and can therefore reshape phytoplankton communities. This study aim to examine how its filtration and ingestion depend on food concentration and food type, by using two contrasting phytoplankton species: the unicellular green alga Chlamydomonas reinhardtii, used as a reference food source, and the filamentous and potentially toxic cyanobacterium Planktothrix rubescens, which is a dominant species in the phytoplankton community of Lake Geneva. In a first experiment, mussels were exposed separately to each alga across a gradient of six chlorophyll-a concentrations (2–100 µg L⁻¹) to characterise their functional response. Clearance rates and Ingestion rates were higher for C. reinhardtii than for P. rubescens at equivalent carbon concentrations, and ingestion of C. reinhardtii followed a Type III (sigmoidal) functional response, whereas no classical model between the three functional response types adequately described the concentration independent ingestion of P. rubescens. In a second experiment, mussel where fed with mixtures of the two species at three ratios (25:75, 50:50, 75:25 P. rubescens:C. reinhardtii) across the same concentration gradient. Selective feeding on C. reinhardtii persisted when it represented at least half of the diet, but this preference weakened when P. rubescens dominated the mixture. This suggest either a dilution effect or an inhibitory effect of the cyanobacterium on the overall filtration. Together, these results indicate that quagga mussels discriminate against P. rubescens, suggesting that their ongoing invasion of Lake Geneva may reinforce the dominance of this cyanobacterium, with implications for phytoplankton community structure in a lake already affected by climate change and incomplete winter mixing. Dewey 550 Dewey 570 30 Section de biologie 16 41 Département F.-A. Forel des sciences de l'environnement et de l'eau 153 false 5ec666a6-e988-4000-8d4b-94980d7ce486 Master thesis Restricted REBECCHI_Nina_master_thesis_final.pdf 3676560 application/pdf c9e2d02bfaa4f814475a2a774817de07c7a2786acd70087e0390fc168e5a55b9 restrictedAccess Faculté des sciences / Section de biologie Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département F.-A. Forel des sciences de l'environnement et de l'eau

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Feeding behaviour of Dreissena rostriformis bugensis: functional response and selective feeding in Lake Geneva				2026	1	0

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