[en] The impacts of a hypothetical CO₂ gas leak from freshwater sediments on the survival and reproduction of freshwater flea Daphnia magna were analyzed. Another objective was to assess the performance of standard toxicity testing protocols for CO₂-induced acidification research in freshwaters. Four pH levels (7.5, 7.0, 6.5, and 6.0) and two sediments with different contamination level were tested. The results revealed that the D. magna are susceptible to a gradual but relatively rapid CO₂ enrichment of the water column causing a change from circumneutral to acidic conditions. Standard 48-h immobilization test with D. magna tended to underestimate the toxicity at CO₂-induced acidity condition. Dissolved aluminum may be implicated in the toxicity to the parental daphnids exposed. Metal outflux from sediments and behavior in elutriate have been discussed.

[en] Highlights: • Coal tar-based paint composition includes metals and PAH. • Chemicals are leached from coated pillars to seawater on different release rates. • PAH bioaccumulated in tissues of oysters experimentally exposed to paint pillars. • Exposed organisms presented physiological stress. • It is recommended that risk assessment of the coal tar-based paints be performed. Products coal tar-based are largely used as concrete structures as protective coatings but some questions about leaching and potential toxic effects remain unclear. A laboratory experiment exposing oysters to miniaturized concrete pillars painted with Lackpoxi N1761 over time was performed and trace elements and 17 PAH were monitored in seawater exposure media, and oyster tissues. The original paint composition was also analyzed, and high concentrations of trace elements and PAH were detected. Sharp increases in PAH concentrations were observed after 6–96 h in exposure media and oyster tissues, suggesting that these compounds were leached from the painted structures. In parallel, the integrity of the hemocytes lysosomal membranes of exposed organisms has been damaged. Based on the response of this biomarker, the use of Lackpoxi N1761 is potentially harmful to the environment and it is required that coal tar-based paints be evaluated according to the environmental risk assessment protocols.