The interactions between organisms and MP are deeply investigated in marine habitats rather than in freshwaters 14. MP enter freshwater systems through diffuse (wind deposition and run-off) or point (wastewater treatment plants and improper disposal of litter) sources 8. rivers) are among the main pathways of plastic release to the oceans 12, 13. Despite this, it has been highlighted that freshwaters ( i.e. In aquatic ecosystems, most of the studies have focused on marine environment rather than freshwaters 9, 10, 11. MP are widespread worldwide in all systems: from aquatic to terrestrial, including atmospheric one 8. The most common shapes are fragments (three-dimensional shape), films (thin and flat foil), fibres (linear), beads and foams 7.
MP are a highly variable class of contaminants, which are characterised by different shapes and colours 6. physical, chemical or biological degradation) of litter in water 5. Primary MP are industrially manufactured, such as microbeads used in cosmetic products (scrubs, toothpaste, etc.), while secondary MP originate from the fragmentation of larger plastic items, for example due to the environmental exposure ( i.e. Moreover, MP can be classified into primary and secondary depending on their origin. In particular, microplastics (MP) range from 1 µm to 5 mm and can be subdivided into large MP (lMP, 1–5 mm) and small MP (sMP, 1 µm–1 mm) 3, 4. Plastics are synthetic organic polymers whose production is steadily increasing throughout recent years 1, becoming an issue of growing concern in the Anthropocene, with fly ash, radionuclides, metals, pesticides and greenhouse gases 2. Also, further investigations are needed to understand the potentialities of using plastics by benthic macroinvertebrates. Further studies ought to be conducted to understand the chronic perturbation on larvae fitness and for example, on drift behaviour. Indeed, larvae appear to not necessarily perceive microplastics as a direct stressor. Our research highlights that macroinvertebrate larvae would use naturally occurring microplastics and this could be of particular concern in freshwaters with high contamination by plastics. Moreover, we provide the first evidence that mayflies burrow mainly in microplastic substrates rather than in natural ones. Particularly, all caddisflies rebuilt cases using the microplastic polymers provided instead of natural items only. Our findings highlighted how microplastics affected both caddisflies in rebuilding its own case (after having removed the natural one) and mayflies burrowing. Three different experimental designs were performed on caddisflies and mayflies by exposing their larvae to natural and microplastic substrates. In this context, we propose timely indoor observations on the exposure of caddisfly Odontocerum albicorne and mayfly Ephemera danica to various microplastic polymers (ABS, PET, PP, PS, PVDF). Regarding the latter habitat, it seems surprising how the plastic effects on benthic invertebrates are neglected since macroinvertebrates have a long tradition in the water quality assessment activities.
Plastics are to date considered one of the main detrimental drivers for the health of aquatic ecosystems, both in marine and inland waters.