PVC and PET microplastics in caddisfly (Lepidostoma basale) cases reduce case stability

Abstract

Caddisfly larvae occur in streams and rivers, and many caddisfly species build protective cases using material from their habitat such as sand grains. At the same time, microplastics (MPs) are regularly deposited in aquatic sediments and are incorporated into caddisfly (Lepidostoma basale) cases in the field. However, it is unknown what the effects of MP incorporation into cases might be on the health of the caddisfly larvae. Hence, we offered two commonly used MPs (polyvinyl chloride (PVC) and polyethylene terephthalate (PET)) to L. basale larvae during a laboratory experiment. Both plastic types have a high density and co-occur with L. basale larvae in benthic habitats. In our experiment, L. basale actively used sand, PET and PVC MPs for building tube-like portable or emergency cases. The latter is a temporary shelter under which the larva can hide for immediate protection. Furthermore, case stability decreased with increasing PVC and PET particle content in the cases, suggesting that MPs may threaten caddisflies by destabilising cases. When case stability is reduced, the protective function of the cases is limited and the larvae may be more prone to predation. Additionally, larvae may be washed away by the current as plastic is lighter than sand. Both effects could limit the caddisfly's survival, which could have far-reaching consequences as caddisfly larvae are important primary consumers in aquatic ecosystems.

Preliminary indoor evidences of microplastic effects on freshwater benthic macroinvertebrates

“…In addition, two studies were conducted on MP in caddisflies: the first one assessed lethal effects of MP on Sericostoma pyrenaicum (Pictet, 1865) at high concentration, i.e. 10 3 particles ml −1 56 and the second one highlighted how polyvinyl chloride (PVC) and polyethylene terephthalate (PET) MP reduced case stability in L. basale 57 .…”

Lethal and Sublethal Responses of Hydropsyche pellucidula (Insecta, Trichoptera) to Commercial Polypropylene Microplastics after Different Preconditioning Treatments

“…Based on such an assumption, significant negative effects on organisms occur only when the microplastics dose with which organisms are challenged exceeds organism-specific toxicological thresholds [ 76 ]. Furthermore, a recent study highlighted how caddisflies and mayflies seem to use mainly microplastics over natural construction materials or substrates [ 78 ], threatening caddisflies by destabilizing their cases [ 79 ].…”

Microplastics in Water, Sediments and Macroinvertebrates in a Small River of NW Spain

“…On the other hand, in water samples, MPs were detected at all three studied points. G2 was the point with the highest abundance of MPs ( 19), followed by G1 (12) and G3 (2) to a lesser extent. All the microplastics collected in this study were bers and fragments of 4 different colors (Fig.…”

“…This process is reversible, and these pollutants can be released upon ingestion, causing substantial damage in different organisms (Rochman et al, 2014). Regarding freshwater ecosystems, recent studies by Ehlers et al (2019Ehlers et al ( , 2020 found that MPs can be used by different species of caddis ies, which incorporate these particles into their cases. The respective caddis y larvae build portable cases in which they develop during their larval stage.…”