Do microplastic particles affect Daphnia magna at the morphological, life history and molecular level?

Abstract

Microplastic particles are ubiquitous not only in marine but also in freshwater ecosystems. However, the impacts of microplastics, consisting of a large variety of synthetic polymers, on freshwater organisms remains poorly understood. We examined the effects of two polymer mixtures on the morphology, life history and on the molecular level of the waterflea Daphnia magna (three different clones). Microplastic particles of ~40 μm were supplied at a low concentration (1% of the food particles) leading to an average of ~30 particles in the digestive tract which reflects a high microplastic contamination but still resembles a natural situation. Neither increased mortality nor changes on the morphological (body length, width and tail spine length) or reproductive parameters were observed for adult Daphnia. The analyses of juvenile Daphnia revealed a variety of small and rather subtle responses of morphological traits (body length, width and tail spine length). For adult Daphnia, alterations in expression of genes related to stress responses (i.e. HSP60, HSP70 & GST) as well as of other genes involved in body function and body composition (i.e. SERCA) were observed already 48h after exposure. We anticipate that the adverse effects of microplastic might be influenced by many additional factors like size, shape, type and even age of the particles and that the rather weak effects, as detected in a laboratory, may lead to reduced fitness in a natural multi-stressor environment.

Polyester-derived microfibre impacts on the soil-dwelling earthworm Lumbricus terrestris

“…Comparisons of the metal contents of the exposure soil and the MFs, despite the higher detection limits for the MFs, indicate that the presence of the MFs in the soil cause a negligible, if any, increase in the potential for exposure to metals by the earthworms. Therefore it seems likely that an increase of metal content was not the cause of the observed change in mt-2 and hsp70 expression, but perhaps supports the notion that MFs induce a general stress response (Imhof et al, 2017).…”

“…Research shows that MPs are easily ingested by aquatic and terrestrial fauna, and may affect their physiology, reproduction and mortality (e.g. Derraik, 2002;Hodson et al, 2017;Huerta Lwanga et al, 2016b;Imhof et al, 2017;Rillig et al, 2017;Wright et al, 2013). Although MPs have been shown to be sorptive for organic and inorganic pollutants, mass balance calculations indicate that ingestion of MPs is unlikely to be a significant exposure route for such pollutants (Hodson et al, 2017;Koelmans et al, 2016).…”

Significant decline of Daphnia magna population biomass due to microplastic exposure

“…For example, several studies on D. magna report adverse effects, including increased mortality (Aljaibachi and Callaghan, 2018;Jaikumar et al, 2018;Jemec et al, 2016), immobilization (Rehse et al, 2016), reduced feeding rates (Rist et al, 2017), growth (Martins and Guilhermino, 2018) and reduced reproductive capacity (Martins and Guilhermino, 2018;Ogonowski et al, 2016). In contrast, other studies on D. magna found limited or no impacts on the endpoints listed above, for example on mortality (Kokalj et al, 2018;Ogonowski et al, 2016) and reproduction (Aljaibachi and Callaghan, 2018;Imhof et al, 2017). The discrepancy between these studies calls for scientists to further investigate the potential adverse effects of microplastics to D. magna.…”

Embryotoxic and teratogenic effects of polyethylene microbeads found in facial wash products in Zebrafish (Danio rerio)using the Fish Embryo Acute Toxicity Test

“…The Fish Embryo Acute Toxicity Test (FET) is a method used to study chemical toxicity in aquatic ecosystems in vivo [59]. This test (FET) is deemed advantageous for studies that need to observe the fish under varying concentrations of the test solution.…”