Is Zooplankton an Entry Point of Microplastics into the Marine Food Web?

First Evidence of Microplastics Burden in Surface Waters of Budhabalanga Estuary, Chandipur, Eastern India: Potential Threat to Aquatic Ecosystem

Microplastic pollution has emerged as a new global concern because of its ubiquitous and persistent nature. Due to the rising use of plastics and discharge of plastic waste into coastal water bodies from point and non-point sources, the occurrence of microplastics along coastal ecosystems has become very prevalent. The current study is the first of its kind to evaluate the presence of microplastics in the surface water of river estuary along the coast of Odisha. Six GPS-fixed locations were used to collect the surface water samples from the Budhabalanga river estuary in Chandipur, Odisha, India. The samples were then subjected to further investigation to determine the types of microplastics present. The average microplastic abundance, according to our findings, ranged from 9.33 ± 2.11 items L-1 to 28.50 ± 2.77 items L-1. Microplastics come in a variety of colours and shapes, but the most prevalent kind is fibre-shaped and black in colour. The pollution load index of the sampling area was calculated to be 4.25 which is categorized under ecological risk level I. FE-SEM images clearly showed the topology of microplastics and ATR-FTIR analysis confirmed the presence of polyethylene, polypropylene, polyvinyl chloride (PVC), nylon, polycarbonate (PC), ethylene vinyl acetate (EVA) and polystyrene (PS) at sampling stations. Our investigation provides useful information that helps to reduce the ecological risk in habitats connected with contaminated sites, including both aquatic and terrestrial habitats.

Microplastic footprints in sharks and rays: First assessment of microplastic pollution in two cartilaginous fishes, hardnose shark and whitespotted whipray

Microplastic (MP) pollution is an emerging environmental problem worldwide and has caused widespread concern both in terrestrial and aquatic ecosystems due to their potential impacts on the human health, and health of aquatic organisms and the environment. Little is known about the exposure of top marine predators to MP contamination (debris 0.1μm - <5mm, also called MPs). For the first time, MPs have been characterized in carnivore demersal elasmobranch specimens of hardnose shark Carcharhinus macloti, and the whitespotted whipray Maculabatis gerrardi. The specimens were from the Persian Gulf and Sea of Oman, and MPs were extracted from their intestines, gills, and skin. MPs were found in every sampled tissue examined: this is higher pollution than previously reported for elasmobranch. The total MPs for these organs were 12.6 MPs/g body mass of sharks, and 17.8 MPs/g in the whiprays on average. The most common MPs found were fibres (59%), and filaments (35%); pointing towards fishing gears and limited wastewater treatment. Fragments, films, and foams were <2.1 %; a less abundant problem. The most abundant MPs sampled were ∼0.5 mm ≤ L< 1 mm (when the limit of detection was 0.1 mm), and blue was the most common MP color hinting intake due to visual confusion. Polycarbonate and nylon were the most abundant polymers in the MPs recovered. The overall findings show that C. macloti and M. gerrardi are vulnerable to plastic and it reflects the critical state of their habitat.

The nexus of microplastics, food and antimicrobial resistance in the context of aquatic environment: Interdisciplinary linkages of pathways

The exponential rise in plastic production since the mid-20th century has led to the widespread existence of microplastics in various ecosystems, posing significant environmental and health concerns. Microplastics, defined as plastic particles smaller than 5 mm, have infiltrated diverse environments, including oceans, freshwater bodies, and even remote Arctic ice. Their ability to absorb toxic chemicals and serve as vectors for microbial colonization raises concerns about their impacts on aquatic organisms and human health. This review examines the pathways by which microplastics infiltrate the food chain, highlighting their presence in various food items consumed by humans. Furthermore, it explores the nexus between microplastics and antimicrobial resistance (AMR), elucidating how microorganisms inhabiting plastic surfaces facilitate the transmission of antibiotic resistance genes (ARGs). The review underscores the urgent need for interdisciplinary research integrating environmental science, microbiology, public health, and policy to address the multifaceted challenges posed by microplastics. Standardized protocols for sampling and analysis are essential to enable meaningful comparisons across research and regions. By collectively addressing these challenges, we can strive towards a more sustainable and resilient future for ecosystems and human societies.

Occurrence of microplastics in Russell's snapper (Lutjanus russellii) and associated prey species in the Central Gulf of Thailand

Microplastic (MP) contamination in fish may occur via their feeding behavior and ingestion of contaminated prey. This study investigated the presence of MPs in the predator Lutjanus russellii (Russell's snapper) and its prey along the Chumphon coast of the Central Gulf of Thailand. Stomach contents of L. russellii were analyzed to identify its prey species. Prey species were then sampled from the same geographical area as the predator specimens for subsequent MP analysis. The dietary habits of L. russellii classify it as a generalist carnivore, consuming a diverse range of food items, including zooplankton, crustaceans, and small fish. No significant correlation was observed between MP abundance and the weight or length of the predator fish (general linear model, p > 0.05). Black and red fibers were the predominant MP types in both predator and prey, though MP sizes varied among the sampled species. In predator stomachs, the most common polymers were acrylonitrile butadiene styrene (ABS; 26.32%), polyethylene terephthalate (PET; 21.05%), and polyester (PES; 10.53%). Conversely, prey samples were dominated by PES (17.58%), PET (15.38%), and ABS (13.19%). Notably, similarities in MP characteristics (shape, color, average size, and certain polymer types) were observed between L. russellii and Portunus sp. The detection of smaller PET fibers in L. russellii compared to Portunus sp. (Mann-Whitney U-test, p ≤ 0.05) suggests the transfer of MPs to L. russellii through the ingestion of hard-shelled crustacean prey. This study underscores the importance of examining predator-prey interactions to better understand MP contamination pathways in marine ecosystems, particularly in regions like the Gulf of Thailand, where plastic pollution is prevalent. Further research is required to assess the long-term ecological implications of MP transfer within marine food chains.

Zooplankton distribution and its associated hydrology across Indian Sundarbans over the last decade: Insights from current trends and future directions

Zooplankton play a crucial role in estuarine ecosystems by aiding nutrient cycling through trophic chains and contributing to large-scale water filtration. The present review highlights the zooplankton research conducted over the last decade (2014-2024) in the Indian Sundarbans, with a focus on research trends, species distribution, hydrological associations, and long-term monitoring and conservation strategies. The study reveals a surge in zooplankton research after 2019, with an emphasis on both small- and large-scale studies. However, tidal creek/canals remain less explored compared to rivers. A lack of methodological standardization in zooplankton research is evident across the Indian Sundarbans. The Saptamukhi-Thakuran-Matla river stretch exhibited the highest species diversity, with 70 species recorded. Similarly, the tidal creeks and canals of Sagar Island were identified as species-rich habitats, with 63 species reported. Oithona brevicornis was found in seven riverine stretches, while Paracalanus parvus and Labidocera euchaeta were each recorded from six rivers, but Bestiolina similis was mostly reported as the numerically predominant zooplankton species. Salinity emerged as the most influential hydrological factor for zooplankton distribution, followed by dissolved oxygen and water temperature. However, increasing pollution, climate change-induced cyclones, salinization, and human activities are threatening zooplankton communities of the Indian Sundarbans. Furthermore, the review underscores the need for long-term monitoring strategies in the Sundarbans, by addressing the integration of remote sensing method, automated devices, data repositories, and ecological modeling approaches. Additionally, the present review recommends future policies for zooplankton conservation, emphasizing habitat protection, water quality assessment, stakeholder engagement, and securing funding to implement long-term monitoring initiatives.

Mass concentrations, compositions and burial fluxes of nano- and micro-plastics in a multi-species saltmarsh

Plastic pollution poses a serious threat to marine ecosystems; yet quantifying the mass concentrations of nano- and microplastics (NMPs) in saltmarsh sediments at the ocean-land interface remains a critical research gap. Here, the study employed reliable and efficient analytical techniques, namely pressurized liquid extraction and the double-shot model of thermal desorption/pyrolysis-gas chromatography-mass spectrometry, to quantify six different types of NMPs in the sediment of a multi-species saltmarsh, providing the first comprehensive assessment of NMP mass concentration and burial in this saltmarsh environment. The results demonstrate that polyethylene, polyvinyl chloride, and polypropylene dominated the NMP composition in sediments, constituting 72.6%, 17.3%, and 4.5% of the total NMPs, respectively. The measured NMPs represent an anthropogenic intrusion, constituting 0.10%-0.23% of the carbon storage in the saltmarsh. By examining the vertical concentration profiles, this study unveiled the influence of saltmarsh vegetation on NMP deposition in sediments, establishing a connection with local sedimentation patterns and the historical zonation of plant species such as Scirpus mariqueter, Phragmites australis and Spartina alterniflora. These findings underscore the crucial role of saltmarsh vegetation in facilitating NMP settling and retention, highlighting the necessity of considering vegetation dynamics in examining the emerging NMP pollution in coastal wetlands.

Plastics counteract the ability of Antarctic krill to promote the blue carbon pathway in the deep ocean

The Antarctic krill (Euphausia superba) play a critical role in promoting the so-called "blue carbon pathway" by producing a large amount of fast-sinking faecal pellets (FPs) which facilitate the transport of CO2 through the water column. Here we assess how exposure to negatively (PS-COOH) and positively (PS-NH2) charged polystyrene nanoparticles, impacts degradation of krill FPs (i.e. change in peritrophic membrane state, Carbon concentration and Carbon/Nitrogen ratio). Our findings suggest that exposure of nanoplastics, particularly negatively charged particles, increases krill FP degradation. This can result in a potential loss of FP-sequestrated C of up to 27 %, equivalent to up 5.5 Mt. C per productive season (Spring-early Autumn). This study provides new insights into how increasing levels of plastic pollution could affect the natural capital provided by krill FPs. The effect of this emerging anthropogenic contaminant should be considered by international policies focused on climate change mitigation and adaptation.

Can microplastics variability drive the colonization dynamics of periphytic protozoan fauna in marine environments?

In recent years, microplastics have become a global environmental hot topic of concern. To explore the effects of different concentrations of microplastics on colonization dynamics of periphytic protozoan fauna, a 21-day study was conducted in temperature-controlled circulation systems. Periphytic protozoan communities were used as test organisms and exposed to five concentrations of MPs: 0, 1, 5, 25, and 125 mg l-1, identification and enumeration were conducted on days 3, 5, 7, 10, 14 and 21. The results showed that the colonization dynamics were driven by MPs and significantly shifted at concentrations over 5 mg l-1. However, a notable decline in maximum species richness and abundance was observed in the high concentrations of microplastic, along with significant deviations in colonization patterns from the control group (0 mg l-1). Therefore, it is suggested that the colonization dynamics of periphytic protozoa can serve as a bioindicator for assessing microplastic concentrations in marine environments.

Source identification of microplastics in highly urbanized river environments and its implications for watershed management

The extensive use of plastic products has resulted in a significant influx of microplastics into aquatic ecosystems, particularly in highly urbanized areas and their associated river environments. However, the specific pathways and quantities through which these microplastics enter the river environment are still unclear, which poses a challenge in developing effective measures to mitigate their sources. In this paper, the spatiotemporal variations of microplastics from different sources in highly urbanized rivers within the Shenzhen Bay watershed were investigated through field sampling, experimental and statistical analysis, and the measures of microplastic reduction were discussed. The observation results exhibited a negative logarithmic correlation between the abundance of microplastics in river water and monthly rainfall (R = 0.994, MSE = 0.051, p < 0.05). When the monthly rainfall was <6 mm, the abundance of microplastics was absolutely dependent on point sources. While the rainfall exceeded 470 mm, the abundance was absolutely predominantly influenced by nonpoint source microplastics. The annual load of microplastics from the watershed was 5.39 × 1012 items, of which 61.6 % originated from point sources. Among the microplastics from point sources, 92.1 % were derived from fibers generated by textile washing. Fragmented microplastics (41.9 %) were the most common type of microplastics from nonpoint sources, primarily originating from the disintegration and weathering of disposable plastics. In the future, there is an expectation to reduce the microplastic load in the watershed to 15.9 % of the total by improving sewage treatment processes and infrastructure. This study can provide scientific guidance for environmental planning and serve as a warning regarding the impact of microplastics on ecosystems in urbanized areas.

A hidden lethal effect of long microplastic fibres on the coastal copepod Acartia erythraea

We investigated the lethal effects of a long fibrous microplastic (the range of lengths, widths, and thicknesses were 1.5-3.6 mm, 10-16 μm, and 7-8.5 μm, respectively) made of polyethylene terephthalate textile, on the marine copepod Acartia erythraea. In laboratory, starved copepods were observed to take in a piece of fibrous microplastic sedimented on the bottom. While no individual ingested the entire fibre, the tip of the ingested fibre reached deep into the gut of the copepods. This suggests that ingestion was not accidental but purposeful behaviour to take in non-living organic matter as a supplementary food source. All copepods that had the fibre in their mouths eventually died within 24-h because the fibre penetrated deep into the gut, preventing feeding and potentially causing stress. Our finding implies that a single piece of microplastic fibre remaining at the bottom of coastal zones could continue to kill copepods owing to its non-degradability.

Comparative assessment of microplastics and microalgae as vectors of mercury and chlorpyrifos in the copepod Acartia tonsa

Microplastics (MPs) raise concerns not only as pollutants themselves, but also due to their ability to act as vectors of pollutants adsorbed from seawater, transferring them to marine organisms. However, the relevance of MPs as carriers of pollutants compared to microalgae needs further exploration. This study compared the role of MPs (2-10 μm non-oxidized and 10-15 μm oxidized high-density polyethylene) and natural organic particles (Rhodomonas lens microalgae, MA) as carriers of mercury (Hg, 2.3 μg Hg/L) and chlorpyrifos (CPF, 1.0 μg CPF/L) to adult Acartia tonsa copepods, after 24-48 h exposure. Dose-response experiments were first performed with adult female copepods exposed to oxidized MPs (0.25-4.0 mg/L), waterborne Hg (0.01-10.0 μg/L) and Ox MPs + Hg (0.25-4.0 mg oxidized MPs/L + 0.50-8.0 μg Hg/L) for 48 h, to complement previous studies that focused on the pesticide CPF. Effects were evaluated with four replicates for physiological and reproductive responses (6 females/replicate), biochemical techniques (40 individuals/replicate) and Hg/CPF bioaccumulation measurements (1000 individuals/replicate). Copepods accumulated Hg/CPF similarly from dissolved pollutants (6204 ± 2265 ng Hg/g and 1251 ± 646 ng CPF/g) and loaded MPs (3125 ± 1389 ng Hg/g and 1156 ± 266 ng CPF/g), but significantly less from loaded MA (21 ± 8 ng Hg/g and 173 ± 80 ng CPF/g). After 24-48 h, copepods exposed to MPs + Hg/CPF showed generally greater biological effects than those exposed to dissolved Hg/CPF or to MA + Hg/CPF, although differences were not statistically significant. MA + CPF had significantly lower AChE inhibition (1073.4 nmol min-1 mg-1) and MA + Hg lower GRx induction (48.8 nmol min-1 mg-1) compared to MPs + Hg/CPF and dissolved Hg/CPF (182.8-236.4 nmol min-1 mg-1 of AChE and 74.1-101.7 nmol min-1 mg-1 of GRx). Principal component analysis suggested different modes of action for Hg and CPF.

Spatial distribution of small microplastics in the Norwegian Coastal Current

High concentrations of microplastic (MP) particles have been reported in the Arctic Ocean. However, studies on the high-resolution lateral and vertical transport of MPs from the European waters to the Arctic are still scarce. Here, we provide information about the concentrations and compositions of MPs in surface, subsurface, and deeper waters (< 1 m, ∼ 4 m, and 17-1679 m) collected at 18 stations on six transects along the Norwegian Coastal Current (NCC) using an improved Neuston Catamaran, the COntinuos MicroPlastic Automatic Sampling System (COMPASS), and in situ pumps, respectively. FTIR microscopy and spectroscopy were applied to measure MP concentration, polymer composition, and size distribution. Results indicate that the concentrations of small microplastics (SMPs, <300 μm) varied considerably (0-1240 MP m-3) within the water column, with significantly higher concentrations in the surface (189 MP m-3) and subsurface (38 MP m-3) waters compared to deeper waters (16 MP m-3). Furthermore, the average concentration of SMPs in surface water samples was four orders of magnitude higher than the abundance of large microplastics (LMPs, >300 μm), and overall, SMPs <50 μm account for >80 % of all detected MPs. However, no statistically significant geographical patterns were observed in SMP concentrations in surface/subsurface seawaters between the six sampling transects, suggesting a relatively homogeneous horizontal distribution of SMPs in the upper ocean within the NCC/Norwegian Atlantic Current (NwAC) interface. The Lagrangian particle dispersal simulation model further enabled us to assess the large-scale transport of MPs from the Northern European waters to the Arctic.

Microplastic ingestion in marine mesozooplankton species associated with functional feeding traits

Microplastic (MP, <5 mm) contamination in the ocean raises concern for zooplankton, as their prey and MPs fall within the same size range. This study aimed to evaluate the ingestion capacity of MPs among a diverse array of mesozooplankton taxonomic groups and species from the central Mexican Pacific, focusing on two functional traits: trophic group and feeding strategy. A total of 20 taxa belonging to eight taxonomic groups, 13 which were identified to species level, were exposed to microspheres (Ms) ranging in size from 38 to 53 μm, at a concentration of 100 Ms/mL. All experimental treatments were placed in 620 mL bottles and rotated on a plankton wheel for 2 h. The results demonstrate that the capacity to ingest MPs is closely related to the trophic group and the feeding strategy of each species, independent of taxonomic group. Omnivores and omnivore-herbivores which generate feeding currents were the most susceptible to MPs ingestion, while highly carnivorous species with active feeding strategies were the least prone. These findings highlight the importance of evaluating MP ingestion by zooplankton at the species level, due to the variability of feeding strategies within taxonomic groups, and the need for continued trait-based research at the species level. A more detailed understanding of zooplankton feeding behavior, especially in ecologically significant species, could enhance trait-based modeling at a biogeographic scale, predicting areas with the highest risk of MP ingestion by zooplankton communities and evaluating global impacts.

Cellulose Nanofiber Films with Gold Nanoparticles Electrostatically Adsorbed for Facile Surface-Enhanced Raman Scattering Detection

Cellulose nanofiber (CNF) holds great promise in applications such as surface-enhanced Raman scattering (SERS), catalysis, esthesia, and detection. This study aimed to build novel CNF-based SERS substrates through a facile synthetic method. Citrate-reduced gold nanoparticles (AuNPs) were adsorbed on the cationized CNF surface due to electrostatic interactions, and uniform AuNPs@(2,3-epoxypropyl trimethylammonium chloride)EPTMAC@CNF flexible SERS substrates were prepared by a simple vacuum-assisted filtration method. The probe molecule methylene blue was chosen to assess the performance of the CNF-based SERS substrate with a sensitivity up to 10-9 M, superior signal reproducibility (relative standard deviation (RSD) = 4.67%), and storage stability (more than 30 days). Tensile strength tests indicated that the CNF-based films had good mechanical properties. In addition, CNF-based substrates can easily capture and visually identify microplastics in water. These results demonstrate the potential application of the flexible, self-assembled AuNPs@EPTMAC@CNF flexible SERS substrate for prompt and sensitive detection of trace substances.

Assessing Microplastics and Nanoparticles in the Surface Seawater of Venice Lagoon-Part I: Methodology of Research

Microplastics (MPs) and nanoplastics (NPs) both represent significant concerns in environmental sciences. This paper aims to develop a convenient and efficient methodology for the detection and measurement of MPs and nanoparticles from surface seawater and to apply it to the water samples collected from the UNESCO site of Venice and its lagoon, more precisely in the Venice-Lido Port Inlet, Grand Canal under Rialto Bridge, and Saint Marc basin. In this study, MPs were analyzed through optical microscopy for their relative abundance and characterized based on their color, shape, and size classes, while the concentration and the mean of nanoparticles were estimated via the Nanoparticle Tracking Analysis technique. Bulk seawater sampling, combined with filtration through a cascade of stainless-steel sieves and subsequent digestion, facilitates the detection of MPs of relatively small sizes (size classes distribution: >1 mm, 1000-250 μm, 250-125 μm, 125-90 μm, and 90-32 μm), similar to the size of MPs ingested by marine invertebrates and fishes. A protocol for minimizing interference from non-plastic nanoparticles through evaporation, digestion, and filtration processes was proposed to enrich the sample for NPs. The findings contribute to the understanding of the extent and characteristics of MPs and nanoparticle pollution in the Venice Lagoon seawater, highlighting the potential environmental risks associated with these pollutants and the need for coordinated approaches to mitigate them. This article is based on scientific research carried out within the framework of the H2020 In-No-Plastic-Innovative approaches towards prevention, removal and reuse of marine plastic litter project (G.A. ID no. 101000612).

Photochemical reactivity of water-soluble dissolved organic matter from microplastics and microfibers

Plastics in aquatic environments are a source of dissolved organic matter (DOM). However, its production pathways and environmental fate remain poorly understood. This study investigated the yields, characterization, and photochemical reactivities of water-soluble DOM from seven pristine microplastics (MPs) and three microfibers (MFs). We found yields of plastic-derived DOM per unit mass of MPs or MFs, including chromophoric DOM (CDOM) and dissolved organic carbon (DOC), were significantly influenced by polymer chemical structures. Notably, MFs exhibited consistently higher DOM yields compared to MPs. In addition, plastics containing aromatic rings, such as PETE and PS, were found to generate higher CDOM yields, although PVC also showed elevated CDOM yields. The plastic-derived DOM had a diverse molecular size-range, spanning from 60 nm (polyester-DOM) to 937 nm (LDPE-DOM), while Zeta potentials, which were predominantly negatively charged, varied from -42.5 mV (nylon-DOM) to +4.6 mV (LMW-PVC-DOM). Degradation rate constants for CDOM (0.001-0.022 h-1) were generally higher than DOC (0.0009-0.020 h-1), with a shorter half-life for PETE- and PS-derived DOM. The reactivity and degradation kinetics of plastic-derived DOM were notably manifested in changes of fluorescence spectra (excitation-emission matrixes) during photochemical weathering, showing the influence of polymeric composition/structures. This baseline study provides an improved understanding of the characterization and environmental fate of microfiber- and plastic-derived DOM in aquatic environments.

Does water column stratification influence the vertical distribution of microplastics?

Microplastic pollution has been confirmed in all marine compartments. However, information on the sub-surface microplastics (MPs) abundance is still limited. The vertical distribution of MPs can be influenced by water column stratification due to water masses of contrasting density. In this study, we investigated the vertical distribution of MPs in relation to the water column structure at nine sites in the Kattegat/Skagerrak (Denmark) in October 2020.A CTD was used to determine the stratification and pycnocline depth before sampling. Plastic-free pump-filter sampling devices were used to collect MPs from water samples (1-3 m3) at different depths. MPs concentration (MPs m-3) ranged from 18 to 87 MP m-3 (Median: 40 MP m-3; n = 9) in surface waters. In the mid waters, concentrations ranged from 16 to 157 MP m-3 (Median: 31 MP m-3; n = 6), while at deeper depths, concentrations ranged from 13 to 95 MP m-3 (Median: 34 MP m-3; n = 9). There was no significant difference in the concentration of MPs between depths. Regardless of the depth, polyester (47%), polypropylene (24%), polyethylene (10%), and polystyrene (9%) were the dominating polymers. Approximately 94% of the MPs fell within the size range of 11-300 μm across all depths. High-density polymers accounted for 68% of the MPs, while low-density polymers accounted for 32% at all depths. Overall, our results show that MPs are ubiquitous in the water column from surface to deep waters; we did not find any impact of water density on the depth distribution of MPs despite the strong water stratification in the Kattegat/Skagerrak.