Ocean warming and CO2-driven acidification can alter the toxicity of metal-contaminated sediments to the meiofauna community

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 degrees 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.

Automated summary

The interaction effects of trace metal contamination, ocean warming, and CO2-driven acidification on a meiofaunal benthic community were assessed. Microcosm bioassays were conducted under controlled conditions with three fixed factors: metal contamination, temperature, and pH. The results revealed that metal contamination led to a decrease in the densities of major meiobenthic groups, exacerbating negative effects on Nematoda and Copepoda but mitigating effects on Acoelomorpha when combined with temperature rise. CO2-driven acidification increased the density of Acoelomorpha in sediments with lower metal levels, while decreasing Copepod densities regardless of contamination or temperature. This study highlights how temperature rise and CO2-driven acidification interact with trace metals in marine sediments, impacting different benthic biota groups.