Ingestion of micro- and nanoplastics in Daphnia magna – Quantification of body burdens and assessment of feeding rates and reproduction

Abstract

Evidence is increasing that micro- and nanoplastic particles can have adverse effects on aquatic organisms. Exposure studies have so far mainly been qualitative since quantitative measurements of particle ingestion are analytically challenging. The aim of this study was therefore to use a quantitative approach for determining ingestion and egestion of micro- and nanoplastics in Daphnia magna and to analyze the influence of particle size, exposure duration and the presence of food. One week old animals were exposed to 2 μm and 100 nm fluorescent polystyrene beads (1 mg/l) for 24 h, followed by a 24 h egestion period in clean medium. During both phases body burdens of particles were determined by measuring the fluorescence intensity in dissolved tissues. Ingestion and egestion were investigated in the absence and presence of food (6.7·10 cells of Raphidocelis subcapitata per ml). Furthermore, feeding rates of daphnids in response to particle exposure were measured as well as effects on reproduction during a 21 days exposure (at 1 mg/l, 0.5 mg/l and 0.1 mg/l) to investigate potential impairments of physiology. Both particle sizes were readily ingested, but the ingested mass of particles was five times higher for the 2 μm particles than for the 100 nm particles. Complete egestion did not occur within 24 h but generally higher amounts of the 2 μm particles were egested. Animal body burdens of particles were strongly reduced in the presence of food. Daphnid feeding rates decreased by 21% in the presence of 100 nm particles, but no effect on reproduction was found despite high body burdens of particles at the end of 21 days exposure. The lower egestion and decreased feeding rates, caused by the 100 nm particles, could indicate that particles in the nanometer size range are potentially more hazardous to D. magna compared to larger particle sizes.

Brood pouch-mediated polystyrene nanoparticle uptake during Daphnia magna embryogenesis

“…growth) for the offspring or whether the PSNPs are excreted without further harm thus remains unknown in this study. D. magna exposed from the neonatal stage for 21 days to PSNPs (100 nm, 1 mg L À1 ) responded with a decreased feeding rate while reproduction was not affected (Rist, Baun, and Hartmann 2017). In contrast, smaller PSNPs (70 nm) caused lower numbers of neonates and reduced body size (0.22 mg L À1 ) and with malformations (30 mg L À1 ) in D. magna (Besseling et al 2014).…”

Commentary: Tissue accumulation of microplastics in mice and biomarker responses suggest widespread health risks of exposure

“…The lack of any behavioral tests also precludes such a claim. The effect of ingested microplastics on longer term changes in feeding behavior and fecundity as previously observed for invertebrates (Wright et al, 2013;Sussarellu et al, 2016;Rist et al, 2017) were not investigated. These are more important parameters to assess pertaining to chronic exposure to any xenobiotic.…”

Toxicological Evaluation and Quantification of Ingested Metal‐Core Nanoplastic by Daphnia magna Through Fluorescence and Inductively Coupled Plasma‐Mass Spectrometric Methods

“…There are divergences regarding the definition of particle size applied to classify microplastics and nanoplastics (Alimi et al ; Hartmann et al ). However, a broad classification defines particles <5 mm as microplastics and <1 μm as nanoplastics (da Costa et al ; Rist et al ; Alimi et al ; Hartmann et al ). An alternative definition for nanoplastics as particles with at least one dimension between 1 and 100 nm is also frequently cited (Alimi et al ; Mattsson et al ; Pinto da Costa et al ).…”

“…A complete assessment of the toxicological effects of nanoplastics on organisms therefore requires methods for the quantification of the nanoplastics ingested by the organism. In addition, few studies have been conducted to determine the relation between acute and chronic effects on daphnids and the quantification of the ingested plastic particles (Rist et al ; Horton et al ; Liu et al ). In the present study, we propose the quantification of nanoplastics ingested by organisms through 2 methods: 1) a fluorescence method, where a fluorescent monomer was added directly in the styrene polymerization reaction (daphnids were then exposed to the PSNPs, and the nanoparticles ingested by the organisms were quantified through fluorescence light microscopic [green filter] images using ImageJ analysis software), and 2) a total aluminum quantification, where aluminum oxide (Al 2 O 3 ) nanoparticles were used as nucleation seeds in the polystyrene polymerization reaction because of their low toxicity (Brown et al ).…”

“…This method allows the detection and determination of the area of accumulation, and the concentration of fluorescent particles can be calculated by linear regression of a standard curve prepared using a suspension of the particles (Rosenkranz et al 2009). However, this quantification technique is limited by the number of particles and their sizes in relation to the resolution and magnification limits of the microscope used (Rist et al 2017). Some examples of the fluorescent tracers that can be used to quantify plastic particles ingested by D. magna are Nile red (Besseling et al 2014;Lui et al 2016), fluorescein isothiocyanate (Rosenkranz et al 2009), and monomer 7-[4-(trifluoromethyl) coumarin]acrylamide (Booth et al 2016).…”