Microplastics (MPs) in aquatic ecosystems readily promote biofilm formation, creating the plastisphere, a dynamic interface that interacts with environmental pollutants and acts as a reservoir for microorganisms. Recent studies emphasize the plastisphere's contribution to the spread of pathogens, antibiotic-resistant genes (ARGs), and antimicrobial resistance (AMR) within aquatic organisms and across diverse environments, a phenomenon collectively called the ‘Plastiome’. Although the prevalence and effects of the plastisphere have been studied extensively, a systematic synthesis of updated insights into the behavior of the plastiome is urgently needed. This review explores the development and behavior of plastics, focusing on its interactions with ARGs and pathogens within aquatic ecosystems. Microplastics selectively enrich ARGs and pathogenic microorganisms, fostering unique microbial communities distinct from those in surrounding waters. The plastiome facilitates horizontal ARG propagation, increasing the quantity of antibiotic-resistant pathogens and presenting substantial risks to the hydrosphere and public health. Additionally, key research opportunities are identified and strategies are recommended to advance our understanding of plastiome-driven antibiotic resistance in aquatic environments.

Microplastics, a complex category of pollutants containing microorganisms and toxins, pose a significant threat to ecosystems, affecting both biotic and abiotic elements. The plastisphere's bacterial community differs significantly from nearby habitats, suggesting they may significantly contribute to the degradation of plastic waste in the ocean. This study evaluated the diversity of culturable bacterial populations attached to the microplastics in the coastal zones of the A&N Islands and their potential for plastic degradation. Three A&N Islands beaches were surveyed for microplastics. Low-density polyethylene (LDPE) was the most abundant polymer found, followed by Acryl fibre, polyisoprene etc. A total of 24 bacterial isolates were chosen based on their morphological traits and underwent the initial screening processes. With the highest degrading activity (10.79 %), NIOT-MP-52 produced noteworthy results. NIOT-MP-25 (5.07 %), NIOT-MP-43 (3.78 %), NIOT-MP-61 (3.51 %), and NIOT-MP-82 (3.36 %) were the next most active strains. Strain NIOT-MP-52, selected for its superior degradation efficiency, underwent further screening and analysis using FT-IR, SEM, AFM, and DSC. Variations in infrared spectra indicated the breakdown of LDPE while SEM and AFM analyses showed bacterial attachment, roughness, grooves, holes, and pits on the LDPE surface. DSC provided thermal analysis based on the biodegradation potential of the bacterial strain targeting LDPE sheets. These findings highlight the ability of marine bacteria to efficiently degrade microplastics and utilize plastics as an energy source, emphasizing their importance in future plastic waste management.

Halogenated polycyclic aromatic hydrocarbons (HPAHs) including chlorinated (ClPAHs) and brominated (BrPAHs) variants, are emerging contaminants that are considered the next-generation candidates of persistent organic pollutants. Since there was a significant gap exists in understanding of partitioning dynamics of HPAHs between the particulate phase (PP) and dissolved phase (DP) considering many congeners, this study analyzed 75 congeners of parent PAHs and HPAHs (p/HPAHs) in the samples collected from 27 sites from 20 water bodies in Sri Lanka. The results revealed that the mean of the total concentrations of PAHs, ClPAHs, and BrPAHs in the aqueous phase (PP + DP) were 55.79, 1.89, and 0.49 ng/L, respectively. Partition coefficients of HPAHs increased with molecular weight, and pyrene and its halogenated derivatives dominated both phases. A predominance of HPAHs in the DP suggested that their distribution was more influenced by source characteristics than by phase partitioning processes. Most p/HPAHs originated from mixed petroleum and combustion sources, with additional input from decaying contaminated biota. The risk quotients determined via the acute and chronic ecological risk assessment indicated many waterbodies had medium to high risks to fish and daphnids, whereas the consumption of well water for drinking purposes did not pose a risk to humans. This study provides the first comprehensive phase-specific evaluation of HPAHs in a tropical aquatic environment and calls for targeted monitoring strategies, effective management plans, and public awareness to mitigate future contamination.

Studies have shown that halogenated polycyclic aromatic hydrocarbons (HPAHs), including chlorinated (ClPAHs) and brominated PAHs (BrPAHs), could be hazardous pollutants due to their pervasive occurrence in the environment. However, their accumulation properties and toxic potentials in animal feedstuffs remain unclear. This study investigated 75 congeners of parent PAHs, ClPAHs, and BrPAHs in animal-based feed ingredients and fish and swine feeds in Japan using a GC/Orbitrap MS system. The total parent PAHs ranged from below the method detection limit (<MDL) to 2700 ng/g lipid weight (l.w.), with the highest concentration found in fish oil. The total ClPAHs and BrPAHs were in the ranges of <MDL to 104.55 and 0.21–54.38 ng/g l.w., respectively, with their highest concentrations detected in fish meal. The maximum detection frequencies for parent PAHs, ClPAHs, and BrPAHs were detected for fluorene (75 %), trichloropyrene (86 %), and 2-bromonaphthalene (97 %), respectively. The highest ClPAH concentrations were dominated by dichloropyrene (61.92 ng/g l.w., fish meal). The BrPAHs were mostly contributed by 1-bromonaphthalene (33.94 ng/g l.w., animal fat) and 2-bromonaphthalene (22.37 ng/g l.w., fish meal). The toxic assessment estimated for target compounds in various feed ingredients and feed based on the toxic equivalency quotients (TEQs) revealed that HPAHs could additively contribute (up to 100 %) to PAH-like toxic effects. Despite their high detection frequencies and concentrations, several ClPAHs and BrPAHs had no relative toxic potency values. Thus, the TEQs were underestimated, indicating that urgent in-depth research is required to obtain toxicological data for predominant HPAHs.

Aquatic microplastics (MPs) act as reservoirs for microbial communities, fostering the formation of a mobile resistome encompassing diverse antibiotic (ARGs) and biocide/metal resistance genes (BMRGs), and mobile genetic elements (MGEs). This collective genetic repertoire, referred to as the “plastiome,” can potentially perpetuate environmental antimicrobial resistance (AMR). Our study examining two Japanese rivers near Tokyo revealed that waterborne MPs are primarily composed of polyethylene and polypropylene fibers and sheets of diverse origin. Clinically important genera like Exiguobacterium and Eubacterium were notably enriched on MPs. Metagenomic analysis uncovered a 3.46-fold higher enrichment of ARGs on MPs than those in water, with multidrug resistance genes (MDRGs) and BMRGs prevailing, particularly within MPs. Specific ARG and BMRG subtypes linked to resistance to vancomycin, beta-lactams, biocides, arsenic, and mercury showed selective enrichment on MPs. Network analysis revealed intense associations between host genera with ARGs, BMRGs, and MGEs on MPs, emphasizing their role in coselection. In contrast, river water exhibited weaker associations. This study underscores the complex interactions shaping the mobile plastiome in aquatic environments and emphasizes the global imperative for research to comprehend and effectively control AMR within the One Health framework.

Microplastic (MP) pollution is a global concern, yet its presence in riverine environments has received limited research attention. This study aimed to evaluate MP levels and identify their potential sources in river surface water and nearby soil samples from two rural and remote rivers near the Jaldapara National Park in the foothills of Eastern Himalaya of India. The average MP levels in water and soil samples were 0.14 ± 0.11 pieces m−3 and 633.33 ± 124.72 pieces/kg d.w. respectively. The primary types of microplastics detected were fibres, followed by fragments, and films. MP sizes in water were larger than in soil samples. Blue, black, and red MPs were most abundant. Micro-Raman analysis revealed polyethylene was the dominant polymer type, followed by nylon, and polypropylene. Comparatively, pollution levels in the study area were relatively low when compared to other rivers worldwide. Understanding the sources and characteristics of microplastics are vital in formulating effective mitigation strategies and promoting responsible waste management practices. These findings provide valuable insights for policymakers, environmentalists, and indigenous communities to implement measures that can lead to curbing of plastic use and safeguard vulnerable riverine ecosystems from adverse impacts of MP pollution.

Island bays show different physico-chemical characteristics due to their connection with open ocean water and small catchment area, and the same is expected with the biological forms. Phytoplankton size structure significantly influences the function of pelagic food webs and is controlled by the ambient nutrient concentrations. To quantify the relationship between these two in a tropical island bay and to understand the controlling factors, we analyzed the chlorophyll-a concentration by partitioning into three size classes (0.2—2.0 µm, 2.0—20.0 µm and > 20.0 µm) for two seasonal observations in the Andaman Islands. During winter, the nano-phytoplankton (2.0 – 20.0 µm) dominated, while in spring, micro-phytoplankton (> 20.0 µm) dominated. It was observed that the bay had abundant nutrients, but low chlorophyll a concentrations in winter, whereas the scenario reversed in spring. The phytoplankton community exhibited significant seasonal differences between the inner and outer bay areas. The inner bay was dominated by the nano-phytoplankton in winter and micro-phytoplankton in spring, while nano-phytoplankton and pico-phytoplankton dominated the outer bay. The micro-phytoplankton showed a significant seasonal variation, while the other two functional groups did not. During winter, the micro-phytoplankton showed a good correlation with the nutrient silicic acid, and the nanoplankton correlated with nitrite, nitrate, silicate and TN (Total Nitrogen) implying nano-phytoplankton’s reliance on most of the nutrients including organic nutrient. During spring, micro-phytoplankton correlated with the nutrient nitrate, and the nano-phytoplankton correlated with the organic nutrient total nitrogen (TN) implying its reliance on the organic nutrient.

Microplastics (MPs) are ubiquitous in the marine environment, yet information regarding their occurrence in the food web is limited. We investigated the concentration and composition of MPs in water and diverse zooplankton groups from the Arabian Sea basin. Forty-one zooplankton tows were collected with a bongo net (330 μm mesh) from the Arabian Sea in January 2019. MPs in the surface water varied between 0 and 0.055 particles/m3, with a relatively higher concentration (0.013 ± 0.002 particles/m3) in the central Arabian Sea. Though fibrous MPs were most abundant in the seawater (77.14 %), zooplankton prefers small fragments (55.3 %). The size of MPs was distinctly smaller (277.1 ± 46.74 μm) in zooplankton than that in seawater (864.32 ± 73.72 μm), and MPs bioaccumulation was observed in almost all the zooplankton functional groups. Polymer composition revealed polyamide, polyethylene, polypropylene, and PVC were abundant in water and zooplankton, suggesting that the textile, fishing, shipping, and packaging industries are significant sources. The prevailing northeasterly winds, strong West India Coastal Current, and conducive westward radiated Rossby wave during January 2019 have carried the microplastic contaminated water mass away from the coast, posing a threat to the open ocean ecosystems. These results demand further attention to investigate the state of plastic pollution in the Arabian Sea basin.

Major anthropogenic activities surround the Port Blair Bay, while Aerial Bay remains as a pristine environment. A field study was carried out during the south-west monsoon season (July – August, 2011) in the two bays to compare the physicochemical parameters and their effect on phytoplankton community structure. Among the physico-chemical parameters, water temperature (p < 0.01, n = 18), DO (p < 0.01, n = 18) and TP (p < 0.05, n = 18) showed significant variation between the Bays. Salinity and Redfield ratio (N:P) was lower in Aerial Bay as compared to Port Blair Bay; while the Si:N ratio was higher in the Aerial Bay. The average chlorophyll-a concentration as well as species richness was found to be higher in the Port Blair Bay as compared to the Aerial Bay. The highest phytoplankton density and centric diatom abundance were observed in Port Blair Bay. In Aerial Bay, the centric diatoms like Dactyliosolen fragilissimus (44.5 %) and Guinardia flaccida (7.1 %) dominated, while in the Port Blair Bay, the centric diatom Skeletonema costatum (25.0 %) and a pennate diatom Nitzschia closterium (24.3 %) dominated the phytoplankton. The phytoplankton community was influenced by the nutrients from the tidal mud flats and rain-fed rivulets in the Aerial Bay; while, in the Port Blair Bay, the phytoplankton abundance was influenced by nutrients from land runoff, inundated areas and anthropogenic sources.

One of the most significant environmental issues confronting our world is plastic trash, which is of particular concern to the marine environment. The sedimentary record of the planet may likely one day contain a horizon of plastic that can be potentially identified as an Anthropocene marker. Here we report the presence of ‘plastiglomerate’ from coastal habitats located in the Aves Island, Andaman Sea, India. This novel form of plastic pollution forms with the incineration of plastic litter in the environment and then mixing of organic/inorganic composite materials in the molten plastic matrix. The plastic pollutants were collected from the Aves Island beach during marine litter surveys. Micro-Raman (μ-Raman) spectroscopy was used to evaluate and confirm all putative plastic forms. Plastiglomerates were made of a polyethylene (PE) and polyvinyl chloride (PVC) matrix with inclusions of rock and sand. Therefore, our research offers new insight into the intricate process of plastiglomerates formation.

Present study provides first comprehensive results on the residual levels of 19 antimicrobial (AM) residues in 12 Japanese swine manure composting facilities that use open or enclosed types of treatment methods. Tilmicosin (14000 μg/kg d.w.) and tiamulin (15000 μg/kg d.w.) were present in the highest concentrations in manure composts. Morantel (MRT) had the highest detection frequency (100%) in compost, suggesting its ubiquitous usage and resistance to degradation during composting. Sulfamethoxazole had low detection frequencies and concentrations, likely due to limited partitioning to the solid phase. A positive correlation (p < 0.05) between purchasing quantities and residue levels in manure composts was detected for fluoroquinolones (FQs). The removal efficiencies of AMs in enclosed-type facilities were lower and more inconsistent than those in open-type facilities. Tetracyclines (TCs), lincomycin, and trimethoprim were easily removed from open-type facilities, whereas FQs and MRT persisted in both facilities. After discontinuing the usage of oxytetracycline (OTC), TCs concentrations reduced drastically in input materials, remained pseudo-persistent in composts for up to 4 months, suggesting a time lag for composting and were not detected (<10 µg/kg) after 4 months of OTC withdrawal. This study emphasizes on the effectiveness of manure composting methods in reducing AM residues in swine waste.

The limited existing research on the accumulation of hazardous chlorinated and brominated polycyclic aromatic hydrocarbons (ClPAHs and BrPAHs) in micro-mesoplastics (mMPs) motivated this investigation. We collected mMPs from the coastal environments of Sri Lanka and Japan. Out of 75 target compounds analyzed, 61 were detected, with total parent PAH concentrations reaching 16,300 and 1770 ng/g plastic in Sri Lanka and Japan, respectively. The total parent PAH concentrations in mMPs from the southern Sri Lankan coastline were relatively higher than those from the eastern coastline. Phenanthrene and naphthalene were the dominant parent PAH congeners in most mMP samples. Chlorinated pyrenes and brominated naphthalene were predominant among halogenated PAHs. The estimated toxic equivalency quotient (TEQ) ranged from 0.67 to 1057 ng-TEQ/g plastic, with the highest levels observed in polystyrene (PS) particles from the southern Sri Lankan coast. Benzo[a]pyrene and dibenzo[a,h]anthracene exhibited elevated TEQ for parent PAHs, whereas dichloropyrene, and dibromopyrene represented the highest TEQs for ClPAHs and BrPAHs, respectively. The data evidenced that several HPAH congeners can increase the PAH-like toxicity (∼86%) in mMPs. This study provides insights into the accumulation of parent and halogenated PAHs in mMPs, highlighting their potential combined implications in marine and terrestrial ecosystems.

Plastic is a wonder product, perhaps one of humanity's best innovations, and has become an indispensable part of our daily lives. Besides the indisputable benefits of plastic materials, significant concerns arise about plastic leakage to the environment. Tiny plastic particles, so-called microplastics (MP), have been detected ubiquitously in various ecosystems around the globe. They are bioavailable for many organisms and may negatively affect ecosystems and society, and the economy. The present study was conducted at first to understand the nature, behavior, and interactions of microscopic plastic waste in the marine environment.A preliminary study was conducted in the coastal environment from the Andaman Sea to map the current plastic pollution status and establish baseline data MPs in water, sediment, and marine food web. In this work, clear evidence of MP bioaccumulation was observed in the marine food-chain organisms like zooplankton, finfishes, and shellfishes. A high amount of MP retention was observed in the zooplankton community. Maximum MP ingestion was observed in adult carangid fish Carangoides malabaricus (up to 67 micro-particles/fish). FT-IR revealed many anthropogenic polymers like polyethylene, polypropylene, nylon, acrylic, and ionomer surlyn. These results depict that plastic pollution is ubiquitous and reached almost every compartment of the coastal environments.Further, to understand the plastic pollution hotspots in the Indian marine environments, a comparative study was carried out to assess the abundances and characteristics of MPs in the bottom sediments from the continental shelf zone of the Andaman Sea and the Arabian Sea. Surface sediments were collected onboard FORV Sagar Sampada from 14 locations of the Andaman Sea and 8 locations of the Arabian Sea with a depth varied from 76 to 264 m. Microplastics were isolated using density separation methods and were enumerated using light microscopy and epi-fluorescence microscopy. MP concentration ranged from not detected (ND) to 267 particles per kilogram. Mean MP concentration at the Arabian Sea was significantly higher (p < 0.001) than in the Andaman Sea. Among different types of MPs, fiber had the highest distribution, followed by fragment and pellet. The mean MP concentration at the Arabian Sea was significantly higher than the Andaman Sea, suggesting the Arabian Sea experiences more anthropogenic pressures than the former area.The present study revealed the widespread occurrence of MPs throughout the Indian seas. Further, to understand the ecological consequences of these microscopic litters, MP ingestion by oceanic zooplankton of the Arabian Sea was analyzed. Clear evidence of higher amounts of MP ingestion was observed in carnivorous zooplankton than in the herbivorous or omnivorous species. These results suggest that feeding habits play critical roles in the pollutants' availability in the marine environment. The plastic pollution problem is magnifying due to the long-term persistence and prolonged degradation of plastics in the environment. Omnipresent accumulation, persistence, and environmental toxicity of plastic waste warrant immediate action for developing efficient, eco-friendly, and sustainable technologies for their degradation. However, some of the microbes, including bacteria, are capable of synthetic polymer degradation.To understand whether microbes can play a critical role in solving the plastic pollution, 11 marine bacteria with plastic degradation potentials were isolated from the coastal environments of Andaman Island. Further, based on the preliminary screening, a bacterial consortium was prepared with four bacterial strains from the genus Vibrio (2 strains), Paenibacillus, and Bacillus. The bacterial consortium was incubated with low-density polyethylene (LDPE) sheets as sole carbon source and incubated for 120 days. After 120 days of incubation on average, nearly 47% LDPE degradation was observed. These observations were supported with FT-IR, SEM, AFM, NMR, and TG-DSC analysis. These results suggest that the bacterial consortia used in this work may have great potential to degrade plastics and solve the problem. However, further research is required to develop innovative, cutting-edge, and eco-friendly technology to solve plastic pollution.

The presence of pharmaceutically active compounds (PACs) in the environment and their associated hazards is a major global health concern; however, data on these compounds are scarce in developing nations. In the present study, the existence of 39 non-antimicrobial PACs and six of their metabolites in wastewater from hospitals and adjacent surface waters in Sri Lanka was investigated from 2016 to 2018. The highest amounts of the measured chemicals, including the highest concentrations of atorvastatin (14,620 ng/L) and two metabolites, mefenamic acid (12,120 ng/L) and o-desmethyl tramadol (8700 ng/L), were detected in wastewater from the largest facility. Mefenamic acid, gemfibrozil, losartan, cetirizine, carbamazepine, and phenytoin were detected in all the samples. The removal rates in wastewater treatment were 100% for zolpidem, norsertaline, quetiapine, chlorpromazine, and alprazolam. There was substantial variation in removal rates of PACs among facilities, and the overall data suggest that treatment processes in facilities were ineffective and that some PAC concentrations in the effluents were increased. The estimated risk quotients revealed that 14 PACs detected in water samples could pose low to high ecological risk to various aquatic organisms. Compounds such as ibuprofen, tramadol, and chlorpromazine detected in untreated and treated wastewater at these facilities pose a high risk to several aquatic organisms. Our study provides novel monitoring data for non-antimicrobial PAC abundance and the associated potential ecological risk related to hospitals and urban surface waters in Sri Lanka and further offers valuable information on pre–COVID-19 era PAC distribution in the country. Environ Toxicol Chem 2022;41:298–311. © 2021 SETAC.

The omnipresent accumulation and non-degradable nature of plastics in the environment are posing an ever-increasing ecological threat. In this study, a total of 97 bacteria were isolated from macroplastic debris collected from the coastal environments of Andaman Island. The isolates were screened for LDPE degradation potential and were identified based on phenotypic, biochemical, and molecular characterization. 16S rDNA-based identification revealed that three-three isolates of each belong to the genus Oceanimonas and Vibrio, two were closely related to the genus Paenibacillus whereas, one-one was associated with the genus Shewanella, Rheinheimera, and Bacillus, respectively. A bacterial consortium was formulated using the top four isolates based on their individual LDPE degradation potentials. A significant increase (p < 0.05) in the mean LDPE degradation (47.07 ± 6.67% weight-loss) and change in thickness was observed after 120 days of incubation. FTIR spectrum, 13C NMR, and TG-DSC analyses demonstrated changes in the LDPE sheets' functional groups, crystallinity, and in thermal properties after 120 days of incubation. The SEM and AFM images confirmed bacterial attachments, an increase in surface roughness and deformities on LDPE sheets. This study reports a bacterial consortium that can efficiently degrade the plastics and can be used in providing eco-friendly mitigation of plastic waste.

Recent reports of the presence of halogenated derivatives of polycyclic aromatic hydrocarbons (PAHs) in human foods of animal origin, such as chlorinated (ClPAHs) and brominated (BrPAHs) PAHs, suggest that their contamination in dairy products may also pose a human health risk. This study used GC/Orbitrap-MS to analyze 75 congeners of halogenated PAHs and parent PAHs in milk and creaming powder samples commonly found in grocery stores in Sri Lanka and Japan. Our investigation revealed a total of 31 halogenated PAHs (HPAHs) in the samples. The concentrations of total parent PAHs in the samples from Sri Lanka and Japan ranged from not detected (n.d.)–0.13 and <0.001–16 ng/g dry weight (d.w.). Total ClPAHs and BrPAHs in the samples ranged from 0.01–3.35 and 1.20–5.15 ng/g (d.w.) for Sri Lanka, and 0.04–2.54 and n.d.–2.03 ng/g d.w. for Japan, respectively. The ClPAHs were dominated by chlorinated-pyrene, -fluoranthene, and -benzo[a]pyrene congeners, whereas the BrPAHs were dominated by brominated-naphthalene and -pyrene congeners. The toxic assessment estimated based on the intake of toxic equivalency quotients (TEQs) for target compounds in milk powders revealed that HPAHs might contribute additively to the PAHs-associated health risk to humans, indicating that more research is needed.

The marine environment is most vital and flexible with continual variations in salinity, temperature, and pressure. As a result, bacteria living in such an environment maintain the adaption mechanisms that are inherent in unstable environmental conditions. The harboring of metal-resistant genes in marine bacteria contributes to their effectiveness in metal remediation relative to their terrestrial counterparts. A total of four mercury-resistant bacteria (MRB) i.e. NIOT-EQR_J7 (Alcanivorax xenomutans); NIOT-EQR_J248 and NIOT-EQR_J251 (Halomonas sp.); and NIOT-EQR_J258 (Marinobacter hydrocarbonoclasticus) were isolated from the equatorial region of the Indian Ocean (ERIO) and identified by analyzing the 16S rDNA sequence. The MRBs can reduce up to 70% of Hg(II). The mercuric reductase (merA) gene was amplified and the mercury (Hg) volatilization was confirmed by the X-ray film method. The outcomes obtained from ICP-MS validated that the Halomonas sp. NIOT-EQR_J251 was more proficient in removing the Hg from culture media than other isolates. Fourier transform infrared (FT-IR) spectroscopy results revealed alteration in several functional groups attributing to the Hg tolerance and reduction. The Gas Chromatography-Mass Spectrometry (GC-MS) analysis confirmed that strain Halomonas sp. (NIOT-EQR_J248 and NIOT-EQR_J251) released Isooctyl thioglycolate (IOTG) compound under mercury stress. The molecular docking results suggested that IOTG can efficiently bind with the glutathione S-transferase (GST) enzyme. A pathway has been hypothesized based on the GC-MS metabolic profile and molecular docking results, suggesting that the compound IOTG may mediate mercuric reduction via merA-GST related detoxification pathway.

Microplastics (MPs) are widely-recognized contaminants and marine sediments act as a sink of MPs and therefore may cause a potential threat to benthic communities. We aim to analyze the MPs abundances and characteristics in the seafloor sediments from the continental shelves of the Arabian and Andaman seas. Twenty-two seafloor sediments were collected from 8 and 14 locations of the Arabian and Andaman seas, respectively. MPs concentrations varied from not detected (ND) to 267 particles kg−1 with mean values of 128.02 ± 33.92 and 15.36 ± 2.61 particles kg−1, respectively for the Arabian and Andaman seas. Among different shapes, fiber had the highest distribution over fragments and pellet. FT-IR analysis revealed acrylic was most dominant polymer, followed by polyethylene, and nylon. Mean MP concentration at the Arabian Sea was significantly higher (p < 0.001) than in the Andaman Sea. The present study revealed the wide-spread occurrence of MPs throughout the Indian seas.

Ten representative fresh rock samples distributed sparsely were collected in each station’s viz., Rutland Island (RT), Chidyatapu (CT), Burmanallah (BN), Carbyn’s cove (CC), Redskin Island (RS), Wandoor (WD), Guptapara (GP), Manjery (MJ), Shipighat (SG), and Junglighat (JG) in South Andaman island for identifying the background values of the trace metal(loid)s viz., V, Cr, Co, Ni, Cu, Zn, Zr, Pb, As, and Fe. Correspondingly, quadruplet samples of mangrove sediments from those ten stations were studied for the aforementioned trace metal(loid)s. Incidence of trace metal(loid)s in rock and mangrove sediments were assessed using wavelength dispersive X-ray fluorescence (WD-XRF) spectrometry. Geo-chemical indices such as enrichment factor (EF), contamination factor (CF), geo-accumulation index (Igeo), and anthropogenic factor (AF) were used to gauge the levels of trace metal(loid)s in mangrove sediments. The results suggest that the incidence of various trace metal(loid)s in the mangrove sediments are from the adjacent host rock (AHR) in all the stations except station JG. The computed values EF, CF, Igeo, and AF articulate that station JG exhibits minor enrichment, considerable contamination, moderately polluted, and anthropogenic influence respectively.

The presence of antimicrobials, antimicrobial-resistant bacteria (ARB), and the associated antimicrobial resistance genes (ARGs) in the environment is a global health concern. In this study, the concentrations of 25 antimicrobials, the resistance of Escherichia coli (E. coli) strains in response to the selection pressure imposed by 15 antimicrobials, and enrichment of 20 ARGs in E. coli isolated from hospital wastewaters and surface waters were investigated from 2016 to 2018. In hospital wastewaters, clarithromycin was detected at the highest concentration followed by sulfamethoxazole and sulfapyridine. Approximately 80% of the E. coli isolates were resistant, while 14% of the isolates exhibited intermediate resistance against the tested antimicrobial agents. Approximately 61% of the examined isolates were categorized as multidrug-resistant bacteria. The overall abundance of phenotypes that were resistant toward drugs was in the following order: β-lactams, tetracycline, quinolones, sulfamethoxazole/trimethoprim, aminoglycosides, and chloramphenicol. The data showed that the E. coli isolates frequently harbored blaTEM, blaCTX-M, tetA, qnrS, and sul2. These results indicated that personal care products were significantly associated with the presence of several resistant phenotypes and resistance genes, implying their role in co-association with multidrug resistance. Statistical analysis also indicated a disparity specific to the site, treatment, and year in the data describing the prevalence of ARB and ARGs and their release into downstream waters. This study provides novel insights into the abundance of antimicrobial, ARB and ARGs in Sri Lanka, and could further offer invaluable information that can be integrated into global antimicrobial resistance databases.

An intense heterotrophic dinoflagellate bloom caused by Protoperidinium quinquecorne was observed at Port Blair Bay during May 2017. The bloom appeared during a period of significantly higher (p< 0.05) temperatures (35.85 ±1.66°C) and seawater salinity (33.21 ± 0.27 PSU) than the pre-bloom and post-bloom phase. Subsequently, we investigated the bloom impact on water quality and plankton community structure. Dissolved oxygen (DO) was reduced significantly (p< 0.05) during the bloom phase (4.41 ± 0.71 mg l−1) as compared to the pre-bloom condition (5.80 ± 0.23 mg l−1), suggesting an increase in respiration of heterotrophic bloom-forming dinoflagellate species. Further, a significant (p< 0.05) increase and decrease in silicate (8.36 ±1.27μmol l−1) and chlorophyll-a (0.86 ± 0.7 mg m−3) concentrations, respectively were observed during the bloom phase, that coincided with an increase in P. quinquecorne grazing pressure on the diatom population. Ammonia enrichment was recorded post-bloom, which was associated with anaerobic decomposition of dead bloom biomass. P. quinquecorne population density increased from 20 cells l−1 (pre-bloom) to 3.36x106 cells l−1 (bloom) and contributed up to 99.93% of the total phytoplankton community. P. quinquecorne grazed on micro-diatom and smaller tintinnids, resulting in a significant decrease in their abundance. The cyclopoid copepod Oithona spp. responded positively to the P. quinquecorne population and caused a considerable reduction in their abundance during post-bloom. This heterotrophic bloom was the result of high temperature and salinity conditions, coupled with the availability of preferred prey species (micro-diatom). Future monitoring studies are needed to predict harmful algal blooms (HABs) occurrence and their impact on the coastal fishery.

Microplastic (MP) pollution has become a global concern. We aim to quantify the extent of MP pollution in the coastal ecosystem of the Port Blair Bay, A&N Islands. Water, sediment, zooplankton, finfish, and shellfish samples were collected from the Port Blair Bay and analyzed for the presence of MP. Average concentrations of MP in water, sediment, zooplankton, finfish, and shellfishes were found to be 0.93 ± 0.59 particles per m3, 45.17 ± 25.23 particles per kilogram, 0.12 ± 0.07 pieces per zooplankter and 10.65 ± 7.83 particles per specimen, respectively. High amount of MP retention was observed in the zooplankton community. Maximum MP ingestion was observed in adult Carangoides malabaricus. Fiber was most abundant in water, sediment, and fish samples, followed by fragment and pellet. However, fragments were predominant in zooplankton. Nylon, acrylic, and ionomer surlyn were most abundant polymer types in the bay environment. These results demand further attention to combat plastic pollution in the coastal ecosystem.

Pharmaceuticals and personal care products (PPCPs) are known as an emerging class of water contaminants due to their potential adverse effects on aquatic ecosystems. In this study, we conducted the first nationwide survey to understand the distribution and environmental risk of 72 PPCPs in surface waterways of Sri Lanka. Forty-one out of 72 targeted compounds were detected with total concentrations ranging between 5.49 and 993 ng/L in surface waterways in Sri Lanka. The highest level of PPCP contamination was detected in an ornamental fish farm. Sulfamethoxazole was found with the highest concentration (934 ng/L) followed by N,N-diethyl-meta-toluamide (202 ng/L) and clarithromycin (119 ng/L). Diclofenac, mefenamic acid, ibuprofen, trimethoprim, and erythromycin were detected ubiquitously throughout the country. Our data revealed that hospital and domestic wastewater, and aquaculture activities potentially contribute to the presence of PPCPs in Sri Lankan waterways. The calculated risk quotients indicated that several locations face medium to high ecological risk to aquatic organisms from ibuprofen, sulfamethoxazole, diclofenac, mefenamic acid, tramadol, clarithromycin, ciprofloxacin, triclocarban, and triclosan. The aforementioned compounds could affect aquatic organisms from different trophic levels like algae, crustacean and fish, and also influence the emergence of antibiotic resistant bacteria. These findings emphasize that a wide variety of pharmaceuticals have become pervasive environmental contaminants in the country. This data will serve to expand the inventory of global PPCP pollution. Further monitoring of PPCPs is needed in Sri Lanka in order to identify PPCP point sources and to implement strategies for contaminant reduction in wastewater to protect the aquatic ecosystem, wildlife, and human health.

The concentrations of 27 major and trace elements are determined in surface water samples collected from 48 sites of diverse waterways in four states (Tamil Nadu, Kerala, Karnataka, and Telangana) of South India. The aims of this study are to identify the element distribution, comparatively assess the pollution risk, and evaluate human health risks related to diverse waterways in the study area. The results indicate that elements such as Cr, Se, As, Fe, and Mn are the major pollutants, as their concentrations exceeded the acceptable national and international water quality standards in several sites of Ennore, Adyar, Cooum, Periyar, and Vrishabhavathi rivers. Furthermore, statistical analysis reveals that the Ennore, Adyar, Cooum, Periyar, and Kaveri river basins are affected by various anthropogenic activities, leading to moderate-to-high pollution by As, Cr, Mn, Fe, and Se. Potential pollution sources are industrial waste, sewage intrusion, paint industry waste, and automobile runoff. Overall, the investigated sites are categorized into three major groups: highly, moderately, and least polluted. Risk on human health by metals is then evaluated using hazard quotients (HQs) and carcinogenic risk evaluation; the results indicated that As with HQ >1 is the most hazardous pollutant, which could lead to non-carcinogenic and carcinogenic concerns, particularly in children. This study helps in establishing pollutant loading reduction goal and the total maximum daily loads and consequently contributes to preserving public health and developing water conservation strategies.

In order to categorize the distribution, source, and effects of polycyclic aromatic hydrocarbons (PAHs) in aquatic systems of southern India, chemical and toxicological analyses were performed on surface and core sediments, collected from Adyar river, Cooum river, Ennore estuary, and Pulicat lake near Chennai city. The total PAH concentration in surface sediment ranged from 13 to 31,425 ng/g with a mean value of 4320 ng/g; the concentration was markedly higher in Cooum river compared to that at other sites. The historical PAH dissemination in core samples in the Cooum river, Ennore estuary, and Pulicat lake ranged from 30 to 31,425 ng/g, from 8.6 to 910 ng/g, and from 62 to 546 ng/g, respectively. Surface sediments were predominantly contaminated with low molecular weight (LMW) PAHs. Historical profiles suggest that PAH contamination in the area is now greater than it had been in the past. PAH accumulation in Pulicat lake was distinct from that at other locations where high molecular weight (HMW) PAHs were predominant. DNA damage in HepG2 cells treated with sediment extracts from different locations showed a good correlation with their respective total PAH levels. Statistical analysis revealed that 3-ring and 4-ring PAHs may synergistically contribute to the genotoxic potency compared to others in sediments. The study also showed that a majority of PAHs in the study area indicated a petrogenic origin. Based on the enrichment and toxicological assessment of PAHs in sediments, Cooum river was shown to suffer the highest biological impairment among the studied water bodies.

The present study documents individual and combined sub-lethal effect of one redox active (copper) and one non-redox active (cadmium) metal on green mussel (Perna viridis). The mussels were exposed to 60 μg L-1 of Cu and 150 μg L-1 of Cd (individually and in combination) for 21 days. Histopathological and ultrastructural studies revealed significant metal induced alterations such as vacuolization, fusion of gill lamellae, enhance mucous deposition, hyperplasia and necrosis in gills. Antioxidant enzyme assays revealed significant increase in superoxide dismutase (SOD), glutathione S-transferase (GST) and glutathione peroxidase (GPx) activity. Similarly, single exposure to Cd and Cu caused significant induction in Malate dehydrogenase (MDH) activity. However, combined Cu+Cd exposure modulated suppression in MDH activity. Unlike MDH, Cu and Cd individual exposure resulted in a decrease in esterase (EST) activity, but their combined exposure caused an induction. Non-enzymatic biomarkers such as lipid peroxidation (LPO) and metallothionein (MT) levels showed no significant change in response to Cu exposure, whereas, individual Cd exposure or Cd exposure in combination with Cu caused significant changes in their levels. Comet assay revealed a significant increase in DNA damage upon metal exposure. These results indicate that Cu (redox active) and Cd (non-redox active) can induce measurable physiological, biochemical as well as genotoxic perturbations in mussels even at sub-lethal concentrations. A monitoring programme based on the biomarkers discussed here would be useful to study the effect of metal pollutants reaching the coastal waters. Copyright © 2014 Taylor & Francis Group, LLC.

The present study provides preliminary in-situ data on genetic integrity of marine zooplankton. Paracalanus parvus, Oithona rigida and Euterpina acutifrons were collected during four different seasons (summer, pre-monsoon, monsoon and post-monsoon) from 2011 to 2012 in Ennore and Kovalum estuaries. DNA damage levels in different zooplankton were analyzed by comet assay and were correlated with different environmental stressors. Spatial and temporal variations in DNA damage was observed in all the species. Zooplankton from Ennore estuary showed significantly lower genetic integrity. Particulate, sediment, and zooplankton fractions of Pb, Ni, Cu, Cr and Co were associated with high DNA damage during the period of lowest pH, salinity and dissolved oxygen. Zn and Cd showed lower genotoxic impact than the other metals. Feeding modes strongly influenced the genetic integrity in the zooplankton species studied. These results support the use of comet assay as a tool in effectively monitoring genotoxicity in marine plankton communities.