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Theses

Biodiversity and ecosystem functioning in stressed environments : primary producers and consumers at the basis of marine food webs

Abstract : Biodiversity is increasingly altered by human activities, which has led to considerable research on the consequences of biodiversity loss for ecosystem functioning. The anthropogenic stressors driving the ongoing biodiversity loss are however rarely included into biodiversity-ecosystem functioning experiments. The present thesis analyses the impact of anthropogenic stressors (pesticides, heavy metals) on the biodiversity-ecosystem functioning relation in marine primary producers (diatoms) and consumers (copepods). It was shown that chemical stress alters species evenness rather richness, with a disproportionate effect on functioning if stress causes dominance by tolerant species with a low functional contribution. Stress tolerance and the functional contribution were predictable based on the species’ biological traits, and the effects of stress on ecosystem functioning depended on the correlation of traits predicting species abundance and traits predicting the species’ effect on ecosystem functioning. The biodiversity effect on primary producer biomass production increased under stress due to facilitative interactions (complementarity effect). Stressor-induced biodiversity loss reduced the food quality of primary producers and impaired the energy transfer to the consumer level, highlighting the relevance of stressor-induced biodiversity changers in a trophic context. The thesis ends with a synthetic framework which puts forward the three main effects (selective stress, physiological stress, complementarity) through which anthropogenic stress affects biodiversity-ecosystem functioning relations at the basis of marine food webs.
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Christoph Mensens. Biodiversity and ecosystem functioning in stressed environments : primary producers and consumers at the basis of marine food webs. Biodiversity. Université Pierre et Marie Curie - Paris VI; Rijksuniversiteit te Gent, 2016. English. ⟨NNT : 2016PA066736⟩. ⟨tel-01962942⟩

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