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Data from: Ocean deoxygenation caused non-linear responses in the structure and functioning of benthic ecosystems
Pascal, Ludovic; Cool, Joannie; Archambault, Philippe; Calosi, Piero; Cuenca, André L. R.; Mucci, Alfonso O.; Chaillou, Gwénaëlle — 2023-10-18 <p><span lang="EN-CA">The O<sub>2 </sub>content of the global ocean has been declining progressively over the past decades, mainly because of human activities and global warming. Nevertheless, how long-term deoxygenation affects macrobenthic communities, sediment biogeochemistry and their mutual feedback remains poorly understood. Here, we evaluate the response of the benthic assemblages and biogeochemical functioning to decreasing O<sub>2 </sub>concentrations along the persistent bottom-water dissolved O<sub>2</sub> gradient of the Estuary and Gulf of St. Lawrence (QC, Canada). We report several of non-linear biodiversity and functional responses to decreasing O<sub>2</sub> concentrations, and identify an O<sub>2</sub> threshold that occurs at approximately at 63 µM. Below this threshold, macrobenthic community assemblages change, and bioturbation rates drastically decrease to near zero. Consequently, the sequence of electron acceptors used to metabolize the sedimentary organic matter is squeezed towards the sediment surface while reduced compounds accumulate closer (as much as 0.5 to 2.5 cm depending on the compound) to the sediment-water interface. Our results illustrate the capacity of bioturbating species to compensate for the biogeochemical consequences of hypoxia and can help to predict future changes in benthic ecosystems.</span></p>
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Data from: Meiofauna affect the macrobenthic biodiversity-ecosystem functioning relationship
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Piot, Adeline; Nozais, Christian; Archambault, Philippe — 2014-05-13 The biodiversity–ecosystem functioning (B–EF) relationship has become of main interest in the last few decades, mostly because of the worldwide increase in species extinctions. However, most of these studies only consider species within single size-class or trophic level, thereby most likely underestimating ecosystem complexity. To reach more realistic scenarios, we assessed the role of meiofauna (lower size-class level) on the relationship between macrofaunal biodiversity and multiple benthic ecosystem properties. Experiments took place under controlled conditions using three macrofaunal species (Alitta (formerly Nereis) virens, Macoma balthica and Mya arenaria). A total of eight combinations of zero to three functionally different macrofaunal species were maintained in microcosms for 34 days in either the presence or absence of a different size-class grouping (a meiofaunal mixture). The organic matter content and bacterial abundance in sediments and the oxygen and nutrient (NH4+, NOx-, PO4 3-) fluxes across the sediment-water interface were measured and used as proxies of ecosystem properties. Overall, macrofaunal species richness did not modify any of the measured properties; however, we observed changes associated to the presence of A. virens and M. balthica. This study also revealed a strong impact of the presence of meiofauna on ecosystem properties. They changed interactions between macrofaunal species, which led to modifications in the ecosystem properties. Thus, even if this size-class group has been poorly considered in previous studies, this experiment suggests that future studies should consider the meiofauna with greater attention, particularly in the context of B–EF.

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(Source Repository: Dryad) AND (Author: Archambault, Philippe)

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