Digestion and maternal/paternal transfer of microplastic contaminants in Atlantic cod (Gadus morhua) food web.

Microplastic particles are formed from plastic litter, the most abundant pollutant of the oceans. In addition to contain harmful plastic additives, microplastics have a high surface area to volume ratio and a large potential to accumulate organic toxins. The project PlastiCod has studied the contaminant accumulation on microplastics in the sea and the subsequent effect on Atlantic cod (Gadus morhua). For the field studies, industry polyethylene (PE) was sieved to a particle size of 0.3-0.6 mm, filled in permeable bags and placed in the sea at 9 locations along the coast of Norway by the Bellona Foundation and partners. Plastic sheets were deployed alongside the PE for comparison purposes. The samples were retrieved after about four months and analyzed for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), chlordanerelated pesticides and toxaphene by University of Aarhus. The contaminant concentrations in the PE were generally low. Amongst the PBDEs, for example, only BDE-47 and BDE-99 were widely detectable, and a generally higher concentration for PCBs. There were observed geographical differences, but also indication of local phenomena within a location. Natural contaminated microplastics from one of the locations were used in extruded feeds to farmed broodstock cod at Nofima, as ingested microplastics have shown to give physiological harm to the marine life. However, the low concentration of PBDEs and PCBs sorbed to the microplastics had a low contribution compared to content in the marine ingredients used in the feeds for adult fish. The effect of microplastics ingestion in farmed broodstock fish were studies through sexual maturation autumn 2017 to spawning spring 2018. There were overall observed few significantly effects on the fish biometrics, anatomy or physiology through maturation between the dietary groups. Maternal effect to next generation were furthermore studied, but no effects on egg and larvae quality were observed. Feeding study with PCB and PBDE spiked microplastics through the zooplankton food web showed accumulation of microplastic pollutants in the cod larvae irrespectively of parental relation. Absorption of PCB polluted microplastic are furthermore studied at University of Bergen, both through tube feeding a single meal with microplastic to cod larvae and a feeding study with juveniles autumn 2020. University of Wageningen have published a generic theoretical model that simulates the transfer of microplastics and hydrophobic organic chemicals in Atlantic cod food web. Results for the PlastiCod project will contribute to develop this model further.

The PlastiCod project have given the partners at Nofima and University of Bergen an opportunity to explore a new field of research that has extended our knowledge and increased our interest for the topic. University of Aarhus and Wageningen University has been key partners with its competence in toxicology and environmental ecology, while the Bellona Foundation was a key partner in the sorption study along the coast of Norway. Our main finding have been that contribution of environmental contaminants to microplastics are low in Norwegian waters, and that high-fat food sources contributes with more contaminants compared to microplastics. There are indications that microplastic can lower the contamination burden of food in the fish gut, but at the same time ingestion of microplastic take space from nutrients that can affect amount energy utilized per meal. Pollution hot spots could occur and affect local cod larvae food webs, actions to stop further pollution are of high importance.

Microplastic particles are formed from plastic litter, the most abundant pollutant of the oceans. In addition to contain harmful plastic additives, microplastics have a high surface area to volume ratio and a large potential to accumulate organic toxins. The project PlastiCod has studied the contaminant accumulation on microplastics in the sea and the subsequent effect on Atlantic cod (Gadus morhua). For the field studies, industry polyethylene (PE) was sieved to a particle size of 0.3-0.6 mm, filled in permeable bags and placed in the sea at 9 locations along the coast of Norway by the Bellona Foundation. Plastic sheets were deployed alongside the PE for comparison purposes. The samples were retrieved after about four months and analyzed for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), chlordanerelated pesticides and toxaphene by University of Aarhus. The contaminant concentrations in the PE were generally low. Amongst the PBDEs, for example, only BDE-47 and BDE-99 were widely detectable, and a generally higher concentration for PCBs. There were observed geographical differences, but also indication of local phenomena within a location. Natural contaminated microplastics from one of the locations were used in extruded feeds to farmed broodstock cod at Nofima, as ingested microplastics have shown to give physiological harm to the marine life. However, the low concentration of PBDEs and PCBs sorbed to the microplastics had a low contribution compared to content in the marine ingredients used in the feeds for adult fish. The effect of microplastics ingestion in farmed broodstock fish were studies through sexual maturation autumn 2017 to spawning spring 2018. Maternal effect to next generation are so far not obeserved. Thus, feeding study with PCB and PBDE spiked microplastics showed accumulation of microplastic pollutants in the larvae irrespectively of parental relation. The accumulation of pollutants from microplastics appears not to affect morphometric measures of the larvae, but further studies will be conducted to elicidate potential harmfull effects of these microplastic pollutants. University of Wageningen have published a generic theoretical model that simulates the transfer of microplastics and hydrophobic organic chemicals in Atlantic cod food web. Results for the Plasticod prosject will contribute to develop this model further.