Marine ecosystems are recognized as among the most productive in the world and provide a wide range of natural services. Nearly 40% of the world’s population lives in coastal areas and depends on the benefits provided by marine ecosystems. Microplastic pollutions have become topic of great interest, they have considered an emerging environmental issue of global concern. Marine plastic waste mainly consists of discarded fishing gear such as nets, lines, traps, etc. that are lost, abandoned or deliberately dumped at sea. Their fragmentation could have potentially harmful effects on marine organisms. Therefore, an understanding of the effects of microplastic pollution is necessary for the safety of the marine environment. This work aimed to compare the acute ecotoxicological effects of polypropylene (PP) microplastic (MPs) and his leachates, derived by mussel nets, in three marine crustaceans Tigriopus fulvus, Gammarus aequicauda and Idothea baltica.
Mussel nets were fragmented in an Ultra Turrax IKAWerkeal (Staufen, Germany) and sieving through a standard series of sieves to obtain particles with a size between 20 and 38 μm. The MPs exposure solutions for individual acute tests were 5, 10, 25, 50, and 100 mg/L, while for G. aequicauda 2.5, 5, 10, 25 mg/L. For leaches preparation, mussel nets were cut (1cm ×1cm) and put in a rectangular glass jar, with 700 mL of filtered natural seawater (FNSW 0.45 μm) and 80g plastic material/L. These were maintained in agitation (100 rpm). At the end of the leaching time (20 days), the water filtered at 0.45 μm and toxicity was tested with the marine species selected.
The negative controls were carried out with FNSW and to evaluates the sensitivity of test species, the positive controls were included for each experiment, by using Cd(NO3)2 as reference toxicant at different concentrations.
Each treatment was replicated 3 times with 20 individuals per concentration placed in 700 mL of test solution for G. aequicauda and I. baltica and 10 individuals for T. fulvus in 3 mL.
The negative controls displayed values of mortality ≤15% meeting the acceptability criteria, and LC50 values for the reference toxicants confirmed the sensitivity of the selected species. The responses of all crustaceans tested, even at the highest leachate dilutions (100% dilution), showed no significant acute toxicity effect (p>0.05) of the leachates. On the contrary, PP MPs significantly affect the survival of all crustacean species with LC50 values ranging from 5.27 mg/L for G. aequicauda to 75.80 mg/L for I. baltica (Tab.1)
PP MPs showed a significant impact on all species already at the lowest tested concentrations (p<0.05) (Fig. 1). These results represent an important advance on this topic. However, further chronic studies are need to assess the potential impact of microplastics on alternative endpoints that are better suited to throughout their life cycle.