Effects of multi-stressors on juveniles of the marine fish Pomatoschistus microps: Gold nanoparticles, microplastics and temperature

• Fish exposed to Au-NP had gold in their body and a decreased predatory performance.
• Thus, exposure to Au-NP may negatively affect the health and fitness of P. microps.
• Temperature rise increased gold body burden and interacted with chemicals’ effects.
• The presence of MP did not change the toxic effects of Au-NP to P. microps.

Knowledge on multi-stressors effects required for environmental and human risk assessments is still limited. This study investigated the combined effects of gold nanoparticles (Au-NP), microplastics (MP) and temperature increase on Pomatoschistus microps, an important prey for several higher level predators, including some species edible to humans. Four null hypotheses were tested: H01: P. microps juveniles do not take up Au-NP through the water; H02: Au-NP (ppb range) are not toxic to juveniles; H03: the presence of MP do not influence the effects of Au-NP on juveniles; H04: temperature increase (20–25 °C) does not change the effects of the tested chemicals on juveniles. Wild juveniles were acclimated to laboratory conditions. Then, they were exposed to Au-NP (≈5 nm diameter) and MP (polyethylene spheres, 1–5 μm diameter), alone and in mixture, at 20 °C and 25 °C, in semi-static conditions. After 96 h of exposure to Au-NP, fish had gold in their body (0.129–0.546 μg/g w.w.) leading to H01 refusal. Exposure to Au-NP alone caused a predatory performance decrease (≈−39%, p < 0.05) leading to H02 refusal. MP did not change the Au-NP toxicity leading to H03 acceptance. Temperature rise significantly increased the concentration of gold in fish exposed to Au-NP (≈2.3 fold), and interacted with chemical effects (e.g. glutathione S-transferases activity) leading to H04 refusal. Thus, the results of this study highlight the importance of further investigating the effects of multi-stressors on marine fish, particularly the effects of temperature on the uptake, biotransformation, elimination and effects of nanoparticles and microplastics, either alone or in mixture. This knowledge is most important to improve the basis for environmental and human risk assessments of these environmental contaminants of high concern.