The possible routes of microplastics uptake in sea cucumber Holothuria cinerascens (Brandt, 1835)

Response and adaptation mechanisms of Apostichopus japonicus to single and combined anthropogenic stresses of polystyrene microplastics or cadmium

Microplastics (MPs) have become pervasive in marine ecosystems, exerting detrimental effects on marine life. The concurrent presence and interaction of MPs and heavy metals in aquatic environments could engender more insidious toxicological impacts. This study aimed to elucidate the potential impacts and underlying mechanisms of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined stress (MPs-Cd) on sea cucumbers (Apostichopus japonicus). It focused on the growth, Cd bioaccumulation, oxidative stress responses, immunoenzymatic activities, and metabolic profiles, specifically considering PS-MPs sizes preferentially ingested by these organisms. The high-dose MPs (MH) treatment group exhibited an increase in cadmium bioavailability within the sea cucumbers. Exposure to PS-MPs or Cd triggered the activation of antioxidant defenses and immune responses. PS-MPs and Cd exhibited a synergistic effect on lysozyme (LZM) activity. A total of 149, 316, 211, 197, 215, 619, 434, and 602 differentially expressed metabolites were identified, distinguishing the low-dose MPs (ML), high-dose MPs (MH), low-dose Cd (LCd), low-dose MPs and low-dose Cd (MLLCd), high-dose MPs and low-dose Cd (MHLCd), high-dose Cd (HCd), low-dose MPs and high-dose Cd (MLHCd), high-dose MPs and high-dose Cd (MHHCd) groups, respectively. Metabolomic analyses revealed disruptions in lipid metabolism, nervous system function, signal transduction, and transport and catabolism pathways following exposure to PS-MPs, Cd, and MPs-Cd. Correlation analyses among key differentially expressed metabolites (DEMs) underscored the interregulation among these metabolic pathways. These results offer new perspectives on the distinct and synergistic toxicological impacts of microplastics and cadmium on aquatic species, highlighting the complex interplay between environmental contaminants and their effects on marine life.

Cellular effects of microplastics are influenced by their dimension: Mechanistic relationships and integrated criteria for particles definition

The definition of microplastics (MPs) is nowadays too generic from a biological perspective, since different characteristics of these particles might influence their effects. To provide experimental evidence that size is an important factor to be considered, Mediterranean mussels Mytilus galloprovincialis were exposed to five size classes of polyethylene fragments (PE-MPs, 20-50 μm, 50-100 μm, 100-250 μm, 250-500 μm, 500-1000 μm). After 10 days of exposure, MPs ingestion and mechanistic relationships between particles size and cellular effects were analysed through a wide panel of biological alterations, including immune system responses, cholinergic function, antioxidant system, lipid metabolism and peroxidation. Results were further elaborated through a Weight of Evidence approach, summarizing the overall biological significance of obtained results in a hazard index based on the number and magnitude of variations and their toxicological relevance. PE-MPs 500-1000 μm were identified as the less biologically reactive size class due to the limited ingestion of particles coupled with the lack of biological effects, followed by PE-MPs 250-500 μm, which slightly altered the cholinergic function and lysosomal membranes. Conversely, PE-MPs smaller than 250 μm provoked a more consistent onset of biological alterations in terms of immune system composition and functioning, redox homeostasis, and lipid metabolism. The overall findings of this study highlight the importance of considering the size of particles for monitoring and risk assessment of MPs, introducing a more integrated evaluation of plastic pollution that, beside particles concentration, should adequately weigh those characteristics triggering the onset of biological effects.

A broad-taxa approach as an important concept in ecotoxicological studies and pollution monitoring

Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost-effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long-term effects and ecosystem-wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies. This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad-taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad-taxa approach more feasible, enabling mechanistic studies on non-model organisms. By combining these approaches with in vitro techniques together with the broad-taxa approach, researchers can gain insights into less-explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data-reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem-focused collaboration between diverse scientific disciplines, international standardisation organisations and decision-making bodies, with a focus on transdisciplinary knowledge co-production for the One-Health approach.

Microcosm study of the effects of polyester microfibers on the indigenous marine amphipod (Cyphocaris challengeri) in the Strait of Georgia (BC, Canada)

Microplastics (MP) remain contaminants of great concern in the ocean because of their abundance, prevalence, and threat to marine organisms. Still, there is a great need for studies on the impact of MP on marine zooplankton. Here, we investigated the effects of polyethylene terephthalate (PET) microfibers (Mf) on the survival, Mf ingestion and retention, predation, and fecal pellets (FP) of the marine amphipod (Cyphocaris challengeri) at environmentally relevant concentrations (0, 10, 100, 1000, 10,000 and 50,000 Mf·L-1) and varied exposure time (24, 48 and 72 h). Our study demonstrated that exposure of C. challengeri to PET Mf did not affect their survival. The average number of ingested Mf and the Mf ingestion rate increased significantly with Mf concentrations. Nonetheless, the Mf ingestion rates by C. challengeri decreased significantly between 24 and 72 h in the two highest Mf treatments (10,000 and 50,000 Mf·L-1), suggesting careful rejection of the Mf or reduced feeding activity. Indeed, PET Mf significantly reduced the copepod feeding rate of the amphipods at Mf concentrations ≥1000 Mf·L-1 after 24 and 48 h of exposure duration. Over time, prey intake reduction in amphipods due to Mf ingestion could affect their reproductive outcome, growth, development, and cellular and ecosystem function. The encapsulation of PET Mf into the FP of C. challengeri significantly increased the FP density and sinking velocities, ultimately doubling the transfer rate of the FP from the surface waters to the sediments in SoG. Conversely, ingesting PET microfibers and their incorporation in FP will potentially enhance the role of C. challengeri in the biological C pump and sequestration in SoG. Our study showed that changes in Mf concentration had a more significant effect on C. challengeri Mf ingestion and ingestion rate, prey consumption, FP density and sinking velocity than the exposure time.

Microplastics in marine invertebrates from the Red Sea Coast of Egypt: Abundance, composition, and risks

This study marked the first exploration of microplastics in marine invertebrates in the Red Sea Coast of Egypt. 110 individuals from 11 different species, including Bivalvia, Gastropoda, Echinoidea, and Holothuroidrea, were collected near a popular tourist destination. The average concentrations of microplastics varied among species, ranging from 8.2 to 136.5 items per individual or 0.2 to 18.1 items per gram of tissue wet weight, with 100 % occurrence. Bivalves had higher concentrations per gram of tissue compared to sediment dwellers and grazers, with Brachidontes pharaonis showing the highest levels. Actinopyga crassa, a sea cucumber, displayed the highest abundance per individual due to its large size and behavior. The identified plastic polymers suggested sources associated with tourism and maritime activities. The estimated human exposure to microplastics through bivalve consumption was minimal. Further research is needed to examine microplastics contamination in the Red Sea and its potential impacts on ecosystems and human well-being.

Characteristics and Risk Assessment of Microplastics in Water and Mussels Sampled from Cape Town Harbour and Two Oceans Aquarium, South Africa

The aim of this study was to measure the characteristics and risk assessment of microplastics (MPs) in Cape Town Harbour (CTH) and the Two Oceans Aquarium (TOA) in Cape Town, South Africa from 2018 to 2020. Water and mussel MP samples were analyzed at 3 sites in CTH and TOA, respectively. Microplastics were mainly filamentous, black/grey and 1000-2000 μm in size. A total of 1778 MPs, averaging 7.50 (± 0.6 standard error of the mean, SEM) MPs/unit were recorded. Average MP concentrations were 10.3 ± 1.1 MPs/L in water and 6.27 ± 0.59 MPs/individual or, based on weight, 3.05 ± 1.09 MPs/g soft tissue wet weight in mussels. Average MPs in seawater in CTH (12.08 ± 1.3 SEM MPs/L) was significantly higher (4.61 ± 1.1 MPs/L) than inside the TOA (U = 536, p = 0.04). Various risk assessment calculations indicate that MPs in seawater poses a greater ecological risk than MPs in mussels at the sites sampled.

Fate of Microplastic Fibers in the Coelomic Fluid of the Sea Cucumber Apostichopus japonicus

Sea cucumbers are economical and ecologically important species, playing a crucial role in nutrient recycling in the ocean and providing valuable bioactive compounds for nutrition. Previous research has demonstrated that microplastic fibers, which are widely recognized as emerging contaminants, are transferred to the perivisceral coelomic fluid during respiration in sea cucumbers; however, their fate in sea cucumbers is still not well understood. We tracked the status of sea cucumbers (Apostichopus japonicus) with polyester microplastic fibers in their coelomic fluid in clean water. The results showed that after transferring sea cucumbers to clean water, the number of microplastic fibers transferred significantly decreased in the coelomic fluid, but at least one microplastic fiber was found up to 60 days. In addition, sea cucumbers recovered from the effect of microplastic fiber transfer, as indicated by enzyme levels and histological observations. Furthermore, single microplastic fiber transfer over a 60-day farmed period did not significantly affect the growth of sea cucumbers. However, repetitive microplastic fiber transfer (i.e., twice and thrice a week over 60 days) significantly decreased the growth rate (p < 0.05). Accordingly, increasing microplastic fibers in sea cucumber habitats pose a threat to sea cucumbers because they can disrupt development. Thus, farmers are advised to select locations for farming sea cucumbers where low microplastic fiber concentrations are expected. Environ Toxicol Chem 2023;42:205-212. © 2022 SETAC.

Microplastic in freshwater ecosystem: bioaccumulation, trophic transfer, and biomagnification

Plastic wastes in the environment ultimately reach to the aquatic habitats and become available to aquatic organisms. The pathway of microplastic in aquatic ecosystem is very less investigated specially in freshwater. There have been evidences of MPs ingestion by freshwater biota but the fate of these MPs further in the food chain is unexplored. Thus, we reviewed the status of MPs in freshwater biota and tried to compare the studies to merge the available information, concepts, and perspectives in order to draw a conclusion on bioaccumulation potential, trophic transfer possibilities, biomagnification, and trends of ingesting MPs by the biota. In this review, the previously available information about MPs in aquatic biota is arranged, analyzed, and interpreted to understand all possible routes of MPs in freshwater habitats. The review further provides a better understanding about the lack of information and research gaps that are needed to be explored to develop a solution to the problem of MPs in near future.

Assessing microplastic ingestion and occurrence of bisphenols and phthalates in bivalves, fish and holothurians from a Mediterranean marine protected area

Microplastic (MP) ingestion, along with accumulated plasticizers such as bisphenol A (BPA), bisphenol F (BPF), and bisphenol S (BPS), and phthalates represented by diethyl phthalate (DEP), dibutyl phthalate (DBP) and bis (2-ethylhexyl) phthalate (DEHP), were quantified in bivalves, fish, and holothurians collected from a coastal pristine area at the western Mediterranean Sea. MP ingestion in sediment-feeders holothurians (mean value 12.67 ± 7.31 MPs/individual) was statistically higher than ingestion in bivalves and fish (mean 4.83 ± 5.35 and 3 ± 4.44 MPs/individual, respectively). The main ingested polymers were polyethylene, polypropylene, and polystyrene. The levels of BPS, BPF, and DEHP were highest in bivalves' soft tissue; BPA and DBP had the highest levels in the holothurians' muscle. In addition, the levels of all plasticizers assessed were lowest in fish muscle; only BPA levels in fish were higher than in bivalves, with intermediate values between those of bivalves and holothurians. This study provides data on exposure to MPs and plasticizers of different species inhabiting Cabrera Marine Protected Area (MPA) and highlights the differences in MP ingestion and levels of plasticizers between species with different ecological characteristics and feeding strategies.

Size-dependent transfer of microplastics across the intestinal wall of the echinoid Paracentrotus lividus

The fate and toxicity of ingested marine microplastics (MPs) have been of major concern in aquatic ecotoxicology for the last decade. Although their ingestion by a wide range of marine organisms has been proven, the uptake of MPs within organs is not yet fully understood and relies on the ability of ingested microplastics to transfer from the gut to tissues beyond the digestive wall (i.e., translocation). The present study investigates the in vitro transfer of fluorescent high-density polyethylene particles of different sizes classes (1-5 µm; 10-29 µm; 38-45 µm) across the intestinal wall of the sea urchin Paracentrotus lividus using Ussing chambers. Small microplastics (1-5 µm) were proven to be able to cross the intestinal wall of P. lividus and reach the coelomic fluid, while larger microplastics (≥ 10 µm) were not observed to cross the intestinal wall. Results demonstrate a size-dependent passage of polyethylene microparticles across the intestinal walls of P. lividus for the first time, highlighting the suitability of Ussing chamber systems to study the transfer of MPs across the intestinal wall of animals.

Seasonal heterogeneity and a link to precipitation in the release of microplastic during COVID-19 outbreak from the Greater Jakarta area to Jakarta Bay, Indonesia

To reduce microplastic contamination in the environment, we need to better understand its sources and transit, especially from land to sea. This study examines microplastic contamination in Jakarta's nine river outlets. Microplastics were found in all sampling intervals and areas, ranging from 4.29 to 23.49 particles m^-3. The trend of microplastic contamination tends to increase as the anthropogenic activity towards Jakarta Bay from the eastern side of the bay. Our study found a link between rainfall and the abundance of microplastic particles in all river outlets studied. This investigation found polyethylene, polystyrene, and polypropylene in large proportion due to their widespread use in normal daily life and industrial applications. Our research observed an increase in microplastic fibers made of polypropylene over time. We suspect a relationship between COVID-19 PPE waste and microplastic shift in our study area. More research is needed to establish how and where microplastics enter rivers.

Quantitative and sensitive analysis of polystyrene nanoplastics down to 50 nm by surface-enhanced Raman spectroscopy in water

Despite being an emerging risk to the environment and human health, little is known about the occurrence, formation, transport, and environmental impact of nanoplastics owing to the lack of quantitative and sensitive sensing techniques. Herein, a surface-enhanced Raman spectroscopy (SERS) method was developed for quantitative sensitive nanoplastics analysis, in which KI was added to Ag nanoparticles as a coagulant and cleaner to remove surface impurities. Polystyrene (PS) nanoplastics with four sizes (50, 100, 200, and 500 nm) were used to evaluate the proposed method, which exhibited high sensitivity (detection limit of 6.25 μg/mL for 100 nm PS nanoplastics), interference resistance, good repeatability, and quantitative analysis ability (R² > 0.970). The feasibility of extending the proposed method to real-world water samples was verified using spiked lake water, and satisfactory recovery rates (87.5-110%) were obtained for nanoplastics with different sizes and concentrations. Thus, this study serves as a solid step in the quantitative analysis of nanoplastics, and the findings can be applied to other areas of research on nanoplastics.

Occurrence of microfibres in wild specimens of adult sea urchin Paracentrotus lividus (Lamarck, 1816) from a coastal area of the central Mediterranean Sea

This study investigates the occurrence of anthropogenic fibres inside wild Paracentrotus lividus at a Mediterranean coastal area in 2020. From each sea urchin, the coelomic fluid was directly analysed while digestive tracts and gonads were removed, pre-treated with trypsin (0.3%) and digested with H₂O₂ (10%) before analysis. A total of 260 fibres and 1 fragment were found in 100 specimens, with an average of 2.6 items/individual. Fibres were more abundant in the digestive system, less in gonads and in the coelomic fluid, respectively. Fourier transform infrared (FTIR) analysis of representative fibres identified 67% natural (cotton-based) and 33% synthetic polymers (polyester) suggesting their origin from textiles, possibly released from laundry sewages. Overall, these results encourage further in-depth investigations on fibres accumulation and potential transfer through the trophic chain up to humans.

Microplastics: impacts on corals and other reef organisms

Plastic pollution in a growing problem globally. In addition to the continuous flow of plastic particles to the environment from direct sources, and through the natural wear and tear of items, the plastics that are already there have the potential to breakdown further and therefore provide an immense source of plastic particles. With the continued rise in levels of plastic production, and consequently increasing levels entering our marine environments it is imperative that we understand its impacts. There is evidence microplastic and nanoplastic (MNP) pose a serious threat to all the world's marine ecosystems and biota, across all taxa and trophic levels, having individual- to ecosystem-level impacts, although these impacts are not fully understood. Microplastics (MPs; 0.1–5 mm) have been consistently found associated with the biota, water and sediments of all coral reefs studied, but due to limitations in the current techniques, a knowledge gap exists for the level of nanoplastic (NP; <1 µm). This is of particular concern as it is this size fraction that is thought to pose the greatest risk due to their ability to translocate into different organs and across cell membranes. Furthermore, few studies have examined the interactions of MNP exposure and other anthropogenic stressors such as ocean acidification and rising temperature. To support the decision-making required to protect these ecosystems, an advancement in standardised methods for the assessment of both MP and NPs is essential. This knowledge, and that of predicted levels can then be used to determine potential impacts more accurately.

Microplastic ingestion by the sandfish Holothuria scabra in Lampung and Sumbawa, Indonesia

This study investigated the abundances and characteristics of microplastics in sediments and sandfish (Holothuria scabra) in Lampung and Sumbawa, Indonesia. Microplastics were found in 89.02% of all sandfish samples, with an average abundance of 2.01 ± 1.59 particles individual^-1. The abundance of microplastics was 58.42 ± 24.33 particles kg^-1 in surface sediments. Furthermore, there was a positive relationship between the abundance of microplastics in sandfish and sediments. Fragments and fibers with small-sized microplastics (300-1000 μm) were the most abundant types found in sandfish and sediments. Fourier-transform infrared (FTIR) analysis showed that polyethylene (30.08%), polypropylene (30.08%), polyurethane (12.20%), and polyethylene terephthalate (8.94%) were the most abundant polymers in the samples. Our results strongly indicate that microplastics in Lampung and Sumbawa originate from the fragmentation of large plastics. Better solid waste management in Indonesia is needed to reduce plastic waste leakage, which could become microplastics.

Existence of microplastics in the edible part of the sea cucumber Apostichopus japonicus

Microplastics (MPs; ≤ 5 mm) have become a potential threat to human health due to the widespread detection of MPs in foods consumed by humans. Here, we investigated the potential of MP occurrence in the main edible part of the most valuable species of sea cucumbers (Apostichopus japonicus). Laboratory experiments showed that fluorescent MPs and microfibers (MFs) could transfer into the body wall of the sea cucumber. The evidence revealed that these MPs enter the body wall via the outer surface. Although these MPs decreased after the sea cucumbers were transferred to clean water, traces of MPs (at least one MP particle) were found up to 60 d post-transfer. To validate these laboratory observations, sea cucumber samples were collected from the field. MPs were found in 86% of live and processed sea cucumber samples. The MP abundances in the field samples ranged from 0-15 MPs animal^-1 and 0-2 MP g^-1. The isolated MPs were mainly MFs, constituting 81% of MPs, followed by fragments, films, and beads. Fourier transform infrared spectroscopy revealed that the polymer composition of the isolated MPs mainly included rayon, followed by polyester and chlorinated polyethylene. The findings of this study demonstrated that the body walls of farmed and processed sea cucumbers contain MPs, thus highlighting the need to control MP pollution during the farming and processing of sea cucumbers.

Evaluation of microplastics ingested by sea cucumber Stichopus horrens in Pulau Pangkor, Perak, Malaysia

The widespread presence of microplastics has caused significant concerns on their potential effects on marine ecosystems. Microplastics are classified as plastic products of less than 5 mm in size and are known to be one of the most dangerous aquatic debris to marine species. Sea cucumbers are deposit feeders living in sediment regions and benthic zone that may collect microplastics in low-energy environments. This research aims to evaluate the types of microplastic isolated from the intestine of Stichopus horrens in Malaysia. This species is selected because it is mainly found in this island. Pulau Pangkor is one of the leading tourism destinations on the small islands is facing increasing numbers of tourists and development and it is useful for sustainable study. A total of 20 S. horrens samples collected from Pulau Pangkor, Malaysia were dissected, and their intestines were collected for digestion. Microplastics were extracted using NaOH and filtered using filter paper. Microplastic identification was conducted on the based of the physical characteristics (colour, shape, size) and chemical characterisation was evaluated using FTIR for polymer functional groups. A total of 1446 unit of microplastics were found in S. horrens. Among various types and colours, fibre (90%) and black (59%) were dominant amongst the various particles identified. The majority of microplastics sizes were 0.51 μm and 1-2 μm. Two polymer materials were identified, namely polyethylene and poly(methyl methacrylate). As a conclusion, the findings of the study will serve as primary data for pollution indicators in respective islands. The microplastics could impact the immune system and upset gut's balance of human.

Sophistication in a seemingly simple creature: a review of wild holothurian nutrition in marine ecosystems

Holothurians are marine invertebrates that are among the most widespread benthic megafauna communities by both biomass and abundance in shallow‐water and deep‐sea ecosystems, their functions supporting important ecological services worldwide. Despite their simple appearance as sea cucumbers, holothurians show a wide range of feeding practices. However, information on what and how these animals eat is scattered and potentially confusing. We provide a comprehensive review of holothurian nutrition in coastal and deep‐sea ecosystems. First, we describe morphological aspects of holothurian feeding and the ultrastructure of tentacles. We discuss the two processes for food capture, concluding that mucus adhesion is likely the main method; two mucous cells, type‐1 and type‐2, possibly allow the adhesion and de‐adhesion, respectively, of food particles. Secondly, this review aims to clarify behavioural aspects of holothurian suspension‐ and deposit‐feeding. We discuss the daily feeding cycle, and selective feeding strategies. We conclude that there is selectivity for fine and organically rich particles, and that feeding through the cloaca is also a route for nutrient absorption. Third, we provide a wide description of the diet of holothurians, which can be split into two categories: living and non‐living material. We suggest that Synallactida, Molpadida, Persiculida, Holothuriida and Elasipodida, ingest the same fractions, and emphasise the importance of bacteria in the diet of holothurians.

Mechanism underlying the toxicity of the microplastic fibre transfer in the sea cucumber Apostichopus japonicus

Microscopic plastic particles (0.1 µm-5 mm) are widespread hazardous pollutants, and microfibres (MFs) are their dominant shape in habitats. Previous field and laboratory studies have demonstrated that MFs enter the coelomic fluid of sea cucumbers from the water through the respiratory tree. However, the possible mechanism underlying the toxicity of this process is not well understood. Herein, RNA-Seq was used to examine the responses of the respiratory tree during the MF transfer process in the sea cucumber Apostichopus japonicus. Polyester synthetic MFs were used, and the number of transferred MFs was controlled to the amount reported from the field. The results showed that the MFs altered gene expression as the transfer process increased. The top genes regulated by MF transfer were mainly related to metabolic processes and signal transduction pathways, with upregulated genes following low MF transfer and downregulated genes following high MF transfer. Functional enrichment analysis revealed the pathways in which differentially expressed genes were enriched under different MF transfer scenarios. The transcriptomic findings were further supported by histological observations, which revealed injury and loss of cell components. This study contributes to understanding the effects of MFs in a valuable echinoderm species through transcriptomic and histological examinations.

Microplastics in African ecosystems: Current knowledge, abundance, associated contaminants, techniques, and research needs

Despite Africa ranking top in mismanaged plastic waste, there is insufficient data on the extent of microplastics and its interaction with other contaminants in its ecosystems. Microplastics pollution has been documented globally, however, specific data from the continent is crucial for accurate risk assessment and to drive policies. We critically reviewed 56 articles from 1987 to 2020 and provide an overview of the current knowledge of the abundance and distribution of microplastics and associated contaminants in African aquatic systems and organisms. Most of the studies were carried out in the marine environment and there is currently no available data on the abundance of microplastic pollution in the African terrestrial environment. We show that across all studies, 5-100% of all sampled aquatic organisms contained microplastics. Concerning high levels of microplastics were reported in fish from Egypt compared to other parts of Africa and the world. Across all persistent organic pollutants sampled in microplastics, hopanes and phthalates were present at high concentrations while sodium and zinc were high relative to other trace metals reported. The most frequently occurring plastics were polyethylene followed by polypropylene and polystyrene. We found that most of the studies relied on visual inspection (52%) > FTIR (38%) > Raman spectroscopy (5%) > Scanning electron microscopy (3%) > Differential scanning calorimetry (2%) for identifying microplastics. Major gaps in sampling and identification techniques which may have overestimated or underestimated the current levels were identified. We discuss other research priorities and recommend solutions to address these issues associated with microplastic pollution in Africa.