Biology subjects

Richaume, A.

Publications and source records attributed to Richaume, A..

2 recordsLinked to original sources

bioRxiv2026

Ecological Impacts of Additive-Enriched LDPE Microplastics in Agricultural Soils: Single and Multi-Species Assessments

Low-density polyethylene (LDPE) microplastics (MPs) are the most frequently sampled type of microplastic in agricultural soils, potentially threatening the soil environment. The majority of MPs that have been investigated are produced from standard polymer formulations, for which the nature of the added compounds is often unknown. Furthermore, standard ecotoxicity tests performed on model species are insufficient for assessing the ecological consequences of MPs contamination in soil. This study examined the responses of multiple keystone species to exposure to MPs in interaction with various additives. No significant effects on their growth were observed when organisms were exposed to MPs alone. However, significant reductions in growth occurred when organisms interacted within uncontaminated soil: the introduction of plants reduced potworm biomass by 49 {+/-} 4.1 % while the introduction of potworms reduced earthworm biomass by 41 {+/-} 5.2%. In MP-contaminated soil containing plants, the average individual biomass of potworm increased significantly from 1.16 {+/-} 0.09 mg in uncontaminated conditions to 2.01 {+/-} 0.27 mg. This suggests that MPs limited the negative effects of interactions. Similar patterns were observed for the potworm-earthworm interaction. MPs containing the highest concentrations of additives induced the strongest biological responses. Analysis of soil parameters revealed that these impacts are likely linked to the disruption of nitrogen cycling. Therefore, it is imperative to comprehensively address the interactions between soil organisms and the influence of additives on plastic ecotoxicity in order to better assess the ecological risk posed by MPs.

ecology↗

bioRxiv2026

Vegetation increases CH4 emissions and methanotroph diversity in marine sediments

Seagrass meadows are key blue carbon (C) ecosystems, storing large amounts of organic C over centuries. Their climate benefits may be reduced by methane (CH) emissions, whose microbial and environmental descriptors in Zostera noltei meadows, dominant seagrass in North-Western Europe, remain poorly understood. We studied CH fluxes, CH-producing and consuming microbial communities and sediment physico-chemical parameters in Z. noltei meadows and adjacent bare sediments across seven sites in Arcachon Bay, France. In situ CH fluxes were measured at low tide and microbial communities were characterised using targeted metagenomics of three functional genes (mcrA, mmoX, pmoA) and quantitative PCR. CH fluxes were higher in vegetated than bare sediments (24.4 {+/-} 2.6 vs. 9.4 {+/-} 0.7 {micro}mol m-{superscript 2} d-{superscript 1}). Mixed linear models and random forest analyses identified C accumulation rate and CO2 flux as the strongest positive descriptors of CH fluxes. Vegetated sediments hosted more diverse methanotrophs, while methanogens showed no habitat differences. Four genera (mcrA-Methanolobus, mmoX-Methylocella, pmoA-Methylococcus, Methyloglobulus) emerged as abundant, seagrass-associated, correlated with CH fluxes, and highlighted by models. Functional diversity, especially pmoA richness, was a stronger microbial descriptor of CH fluxes than gene abundance or a specific genus. Findings indicate Z. noltei meadows enhance C burial and CH emission, with methanotroph diversity potentially mitigating CH emissions. Our results provide the first integrated assessment of CH fluxes and their descriptors in Z. noltei meadows, highlighting the intertwined nature of C burial and CH emissions and the need to account for both in blue C climate assessments.

ecology↗