Chronic ingestion of polystyrene microparticles in low doses has no effect on food consumption and growth to the intertidal amphipod Echinogammarus marinus?

Abstract

The ingestion of microplastics (plastic particles <5 mm) has been observed in a range of marine organisms, and adverse effects have been reported in several species after high concentration exposure. However, the long-term effects of low-dose ingestion remains unclear. The aim of this study was thus to assess the chronic effects of low concentrations of polystyrene microparticles to the intertidal amphipod Echinogammarus marinus, using food consumption, growth, and moulting as endpoints. Amphipods were fed a gelatinous algal feed spiked with microbeads (8 μm) in concentrations of ∼0.9, 9 and 99 microplastics/g for 35 days. E. marinus was also analysed for retention of microplastics, and egestion rate was calculated in a separate high-dose feeding experiment. No significant effects were found in the food consumption or growth assays. There was no accumulation of microplastics in the gut, with only one microbead recorded internally in three (8%) of the exposed amphipods. The low number is likely linked to gastrointestinal functions, allowing for easy egestion of indigestible items. This assumption was supported by the observation that after high-dose exposure, 60% of E. marinus egested all microbeads within 24 h. This study suggests that ingesting low concentrations of 8 μm microplastics do not impair the feeding or growth of amphipods along the exposure period. We hope that negative results such as these may further assist in assessing the impact posed by microplastics to marine organisms.

The effects of trophic transfer and environmental factors on microplastic uptake by plaice, Pleuronectes plastessa, and spider crab, Maja squinado

“…Microplastics at the lower end of the 319 size range may also translocate into the tissues (Brennecke et al, 2015;Farrell and Nelson, 2013), resulting in a 320 range of physiological effects such as reduced mobility and survivorship (Tosetto et al, 2016). However, these 321 effects may not be apparent in animals which do not contain large aggregations of microplastic or are not exposed 322 for extended periods (Hämer et al, 2014), as observed in Echinogammarus marinus (Bruck and Ford, 2018) and Uca 323 rapax (Imhof and Laforsch, 2016). 324…”

First Assessment of Plasticizers in Marine Coastal Litter-Feeder Fauna in the Mediterranean Sea

“…Consequently, it can be assumed that the gut passage of microplastics depends on diverse conditions. In lab experiments, Gammarus fossarum and Echinogammarus marinus egested microplastics after 16-48 h [29,30], while Talitrus saltator showed a complete elimination after a week [31].…”

“…Coastal amphipods could ingest plasticizers, or absorb them directly, through microplastics or the organic fraction of sediment. Previous studies have observed the ingestion of microplastics by amphipods and the successive egestion after different intervals of postfeeding time [27][28][29]. Amphipods eliminate microplastics at different rates depending on different factors: 1. the shape and the size of the ingested particles, beads or fibres; 2. the concentration of microplastics in the food, thus in the environment; 3. the rate of feeding, where the faster the feeding, the more rapid the elimination of microplastics [27][28][29].…”

Rapid fragmentation of microplastics by the freshwater amphipod Gammarus duebeni (Lillj.)

“…This is consistent with results from previous studies which observed no mortality after different amounts of microplastics had been ingested by amphipods. For example, no mortality was found after limited uptake (1–2 microplastics/amphipod) of 8 µm PS microbeads by Echinogammarus marinus 24 , 10–45 µm PE microbeads by G. duebeni 25 and 20–500 µm PS fragments by G. pulex 37 . Likewise, no mortality was found after uptake of an average of 10 microplastics/amphipod of 500 × 20 µm PA microfibers, or 32–250 µm biodegradable and acrylic fragments by Gammarus fossarum 38 , 39 .…”

“…For example, factors such as feeding strategies and developmental stage may determine the uptake of microplastics and the subsequent impact on freshwater macroinvertebrates 22 . Ecotoxicological studies have shown that model aquatic organisms such as daphnids and gammarids readily ingest microplastics, possibly mistaking them for food [23][24][25] . For example, ingestion of 2 µm polystyrene microspheres by Daphnia magna was enhanced when food was absent.…”