Microplastics in aquaculture - Potential impacts on inflammatory processes in Nile tilapia.

Aquaculture is essential for meeting the growing global demand for fish consumption. However, the widespread use of plastic and the presence of microplastics in aquaculture systems raise concerns about their impact on fish health and the safety of aquaculture products. This study focused on the Nile tilapia (Oreochromis niloticus), one of the most important aquaculture fish species globally. The aim of this study was to investigate the effects of dietary exposure to a mixture of four conventional fossil fuel-based polymers (microplastics) on the health of adult and juvenile Nile tilapia. Two experiments were conducted, with 36 juvenile tilapia (10-40 g weight) exposed for 30 days and 24 adult tilapia (600-1000 g) exposed for 7 days, the former including a natural particle (kaolin) treatment. In the adult tilapia experiment, no significant effects on intestinal health (Ussing chamber method), oxidative stress, or inflammatory pathways (enzymatic and genetic biomarkers) were observed after exposure to the microplastic mixture. However, in the juvenile tilapia experiment, significant alterations in inflammatory pathways were observed following 30 days of exposure to the microplastic mixture, indicating potential adverse effects on fish health. These results highlight the potential negative impacts of microplastics on fish health and the economics and safety of aquaculture.

Microplastic exposure in aquatic invertebrates can cause significant negative effects compared to natural particles - A meta-analysis.

Many studies have now reported adverse effects of exposure to microplastics in aquatic organisms. Still, relatively few studies have compared the effects of MPs with those of natural particle controls, which makes it difficult to separate particle effects from chemical effects. In this study, we carry out a meta-analysis of 26 studies to compare the effects of MPs and natural particles on aquatic animals using three different endpoints - growth, reproduction, and mortality. This analysis showed that MPs have the capacity to induce more adverse effects on growth, reproduction, and mortality for some taxonomic groups. However, the effects of exposure to MPs are not consistent across each endpoint or between taxonomic groups. We were not able to clearly discern differing impacts resulting from exposure to specific polymer types or shapes, though more negative effects were associated with polylactic acid and polyethylene, as well as fragments as opposed to beads or fibres. Additionally, meta-regression indicated that larger MP sizes, higher experimental temperatures, and longer exposure periods were all generally associated with more adverse effects. Future studies should continue to make use of negative particle controls to allow for better risk assessment of microplastics and nanoplastics in aquatic ecosystems.

Current environmental microplastic levels do not alter emergence behaviour in the intertidal gastropod Littorina littorea.

Microplastic ingestion by intertidal fauna is a well-documented phenomenon, with emphasis on the physiological consequences of microplastic exposure. However, the behavioural effects of microplastic ingestion have not been explored to the same degree, even in species with documented microplastic ingestion. In this study, the predator-avoidance emergence response of Littorina littorea was assessed and related to microplastic levels within the samples. This is a novel approach to microplastic behavioural experiments, whereby current environmental L. littorea microplastic levels are assessed, rather than levels vastly in excess of those recorded under field conditions. The results showed no difference in emergence likelihood or emergence latency related to microplastic abundance, sex, or treatment. However, L. littorea size did have a significant effect on emergence likelihood and emergence latency, with smaller individuals emerging faster and more frequently. This study shows that microplastics, at their current environmental levels, do not seem to affect L. littorea emergence behaviour.