Juvenile fish caging as a tool for assessing microplastics contamination in estuarine fish nursery grounds

Abstract

Estuaries serve as nursery grounds for many marine fish species. However, increasing human activities within estuaries and surrounding areas lead to significant habitat quality degradation for the juveniles. In recent years, plastic pollution has become a global environmental issue as plastic debris are found in all aquatic environments with potential adverse impacts on marine biota. Given the important ecological role of estuaries and implications of microplastics (MP) in ecosystems, here we assess the occurrence, number, size and polymer types of MP ingested by wild and caged juveniles European flounder (Platichthys flesus). We deployed caged fish for one month at five sites in three estuaries in the Eastern English Channel. The Seine estuary, heavily impacted by manmade modifications and one of the most contaminated estuaries in Europe, was compared to two smaller estuaries (Canche and Liane) less impacted by industrial activities. We found that juvenile flounders (7-9 cm) were vulnerable to plastic ingestion. 75% of caged fish and 58% of wild caught fish had the presence of MP items in their digestive tract. Fibers (69%) dominated in the fish's digestive tract at all sites. An average of 2.04 ± 1.93 MP items were ingested by feral juveniles flounder and 1.67 ± 1.43 by caged juveniles flounder. For the caged fish, the three sites impacted by wastewater treatment plant (Liane, Le Havre Harbor and Rouen) were those with the highest percentage of individuals that have ingested MP items. Most of the isolated items were fibers and blue in color. Polymers identified by micro Raman spectroscopy were Polycaprolactam, Polyethylene Terephtalate and Polyurethane. Although other environmental factors may have affected caged fish condition and mortality, we found no significant correlation with the number of ingested MP. However, the high occurrence of MP ingested by juvenile fish on nursery grounds raises concerns on their potential negative effects for fish recruitment success and population renewal. Finally, this study describes, for the first time, the feasibility of using caged juvenile fish as an assessing tool of MP contamination in estuarine nursery grounds.

Microplastics in freshwater fishes: Occurrence, impacts and future perspectives

“…Alternative experimental approaches, such as exposure studies translocating organisms within mesh cages, also provide opportunities to identify how different species respond to different MP levels in the environment, as well as whether previous exposure to MPs may impact susceptibility to future exposure. Similar studies have already been completed in marine systems for blue mussel ( Mytilus edulis , Mytilidae) (Kazour & Amara, 2020) and European flounder ( Platicthys flesus , Pleuronectidae) (Kazour et al, 2018) and are another promising experimental framework for future MP research in freshwater fishes.…”

Microplastic Characterization by Infrared Spectroscopy

“…The global scientific community intensified its focus into MP pollution after early reports in 2004 on detecting MP in sea water and sediments. Researchers have since reported evidence of microplastic contamination seemingly everywhere, e.g., lakes and rivers, beverages, and food supplies (Kazour et al 2018). Although the number of publications on microplastics has increased rapidly in recent years, a standardized procedure for identification/quantification of MP is still lacking, and methodologies used by different research groups vary widely, resulting in largely incomparable data between studies (Renner et al 2018).…”

Not as Bad as It Seems? A Literature Review on the Case of Microplastic Uptake in Fish

“…In their study of seven different North Sea fish species, Foekema et al (2013) were not able to verify any fundamental effect of MP ingestion on the condition of the MP-feeding fish, originating from five of the seven species under investigation. In an assessment of MP uptake by wild and caged juvenile European flounder Platichthys flesus, Kazour et al (2018) also found no significant correlation between the condition and the number of MP particles taken up at different sampling sites in the eastern English Channel. In an Argentinian estuary, a similar observation was made by Arias et al (2019) who did not detect statistically significant differences in the condition of individuals of the whitemouth croaker Micropogonias furnieri with plastic in their GIT in comparison to individuals without MP particles.…”

“…As the focus of this literature review is entirely on in-situ studies, it will report exclusively on the MP-related impacts investigated in those studies under consideration; the analysis of potential effects of MP-ingestion was, however, performed rather infrequently (in 11 of 90 studies). The majority of these studies investigated the impact of MP in the GIT on the condition of the fish based on morphometrics (Supplementary Material): eight studies assessed the condition based on Fulton's condition factor K (Fulton, 1904;Foekema et al, 2013;Rummel et al, 2016;Mizraji et al, 2017;Cardozo et al, 2018;Compa et al, 2018;Kazour et al, 2018;McGoran et al, 2018;Arias et al, 2019), two more studies (Ramos et al, 2012;Dantas et al, 2019) made use of the formula of Richardson's condition factor CF (Richardson et al, 2011). The outcomes of these investigations are equivocal; taking into consideration only the seven reports in which Fulton's K was calculated, one found a statistical significant difference between MP-feeding and non-feeding individuals (Cardozo et al, 2018).…”