Highlights
- Contamination interacted with warming but the effect on density was taxon dependent.
- Warming increased metal effects in nematods and copepods, and decreased in acoelomorphs.
- Copepod densities were lower, and acoelomorphs higher, in the high CO2/low pH scenario.
- Global change studies should consider multispecies exposures in multi-stressor scenarios.

Abstract
Interactive effects of trace metal contamination, ocean warming, and CO2-driven acidification on the structure of a meiofaunal benthic community was assessed. Meiofauna microcosm bioassays were carried out in controlled conditions in a full factorial experimental design which included three fixed factors: metal contamination in the sediment (3 levels of a mixture of Cu, Pb, Zn, and Hg), temperature (26 and 28 °C) and pH (7.6 and 8.1). Metal contamination caused a sharp decrease in the densities of the most abundant meiobenthic groups and interacted with temperature rise, exacerbating deleterious effects for Nematoda and Copepoda, but mitigating effects for Acoelomorpha. CO2-driven acidification resulted in increased acoelomorphs density, but only in sediments with lower levels of metals. Copepod densities, in turn, were lower in the CO2-driven acidification scenario regardless of contamination or temperature. The results obtained in the present study showed that temperature rise and CO2-driven acidification of coastal ocean waters, at environmentally relevant levels, interacts with trace metals in marine sediments, differently affecting the major groups of benthic biota.
Altafim G. L., Vecchio Alves A., Trevizani T. H., Lopes Figueira R. C., Gallucci F. & Brasil Choueri R., 2023. Ocean warming and CO2-driven acidification can alter the toxicity of metal-contaminated sediments to the meiofauna community. Science of the Total Environment 885: 163687. doi: 10.1016/j.scitotenv.2023.163687. Article.