Microplastic fibers transfer from the water to the internal fluid of the sea cucumber Apostichopus japonicus

Abstract

Microplastics (MPs) are small plastic particles less than 5 mm in diameter. MPs in the form of microfibers (MFs) are widely detected in aquatic habitats and are of high environmental concern. Despite many reports on the effects of MFs on marine animals, their effect on sea cucumbers is still unclear. In addition, our previous filed study has shown that MFs may transfer to the coelomic fluid of the sea cucumber Apostichopus japonicus (A. japonicus). Here, we show how MFs transfer to the coelomic fluid of the sea cucumber. We captured the MFs during their transfer from the water to the coelomic fluid through the respiratory tree. A. japonicus ingested in the MFs along with the water during respiration; the MFs got stuck in the respiratory tree or transferred to the coelomic fluid. The transferred MFs increased during 72 h of exposure and persisted for 72 h after the transfer to clean water. Among the immunity indices, lysozyme (LZM) levels increased in response to the transferred MFs, which confirms the defensive role of LZMs against strange substances. Additionally, non-significantly decreased levels of total antioxidant capacity (T-AOC), malondialdehyde (MDA), peroxidase (POD) and phenol oxidase (PPO) were observed at 24 h and 48 h post-exposure, suggesting minimal oxidative imbalance. Furthermore, there were no significant changes in the speed and the total distance moved by A. japonicus post MFs transfer. This study revealed that MFs transfer and accumulate in the coelomic fluid of A. japonicus.

Evaluation of Microplastics Ingested by Sea Cucumber Stichopus Horrens in Pulau Pangkor, Perak, Malaysia

“…The dominant type of plastic debris contained in this sample, accompanied by bre, fragments and lm. In the digestive organs of sea cucumbers, the type of microplastic that is easily transported by waves and reaches the digestive tract accumulates, resulting in digestive tract blockages from the absorption of plastic utensils known as bre (Taylor et al, 2016;Mohsen et al, 2020;Sayogo et al, 2019;Iwalaye et al, 2020). Besides, the abundance of bre was possibly attributed to the common usage of shing equipment, as plastic bres were important raw materials for shing nets and lines (Zhao et al, 2018).…”

Exposure to microplastic fibers does not change fish early life stage development of three-spined sticklebacks (Gasterosteus aculeatus)

“…However, the concentration chosen for the present study is still higher than the concentrations reported from nature that are in the range of 1-10 fibers/L [17,23,24]. Yet, microplastic fiber concentrations used for exposure studies must be a compromise between environmental observations and concentrations that can be maintained as a reproducible and homogenous dispersion of fibers in the water column under laboratory conditions [20]. Furthermore, concentrations of microplastic fibers above currently reported levels can occur in local fiber contamination events, which might become more frequent in the future with rising plastic pollution [25].…”

“…In laboratory exposure studies, microplastic fibers tend to aggregate, settle to the bottom and adhere to the exposure vessels, and very little fibers stay suspended in the water column at low concentrations [20]. These difficulties often lead to the use of high concentrations of microplastics in exposure studies.…”

“…Smaller fibers are thus often neglected in monitoring studies [18] and little is known about their potential environmental impact. We used a concentration of 1 × 10 4 fibers/L, which is in the range of previous exposure studies conducted with adult life stages and microplastic fibers in the water column [19][20][21][22]. However, the concentration chosen for the present study is still higher than the concentrations reported from nature that are in the range of 1-10 fibers/L [17,23,24].…”

Microplastics: impacts on corals and other reef organisms

“…The majority of work to date has been on sea cucumbers. Individuals collected from the wild and experimental conspecifics were shown to ingest MNPs as they fed on sediments [132][133][134], with some studies showing translocation from the gut to the coelomic fluid. Ingestion rates were also found to correlate to water temperature [133] and therefore rising sea surface temperatures may result in increased dietary exposure.…”