The application of histo-cytopathological biomarkers in marine pollution monitoring: a review

Ecological risk assessment of heavy metals in varied matrices of coastal environment of Maharashtra, India, and their effects on forked venus clam, Gafrarium divaricatum (Gmelin, 1791)

The spatial and seasonal variation of heavy metal contamination was assessed in the seawater, sediments, and clam samples collected from Ratnagiri, Bandra, and Aksa Beach, along Maharashtra Coast, India, during the different seasons. The concentrations of eleven heavy metals were analyzed using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and the metal concentrations were found in the order sediment > clam > seawater. Various pollution indices indicated that Cd and As mainly contributed to ecological risks, and Bandra was the most contaminated site. Bioaccumulation studies in intertidal clam, Gafrarium divaricatum (Gmelin, 1791), showed that most heavy metals exceeded permissible limits except Cu and Zn. Histopathological examination of the clam tissues revealed hemocyte infiltration, damage in cilia and lamellae of the gills, tubular atrophy, and necrosis in the digestive glands. The findings of this research highlight the potential of G. divaricatum as a reliable bioindicator species for biomonitoring and sustainable management of coastal ecosystems.

Using digital pathology to standardize and automate histological evaluations of environmental samples

Histological evaluations of tissues are commonly used in environmental monitoring studies to assess the health and fitness status of populations or even whole ecosystems. Although traditional histology can be cost-effective, there is a shortage of proficient histopathologists and results can often be subjective between operators, leading to variance. Digital pathology is a powerful diagnostic tool that has already significantly transformed research in human health but has rarely been applied to environmental studies. Digital analyses of whole slide images introduce possibilities of highly standardized histopathological evaluations, as well as the use of artificial intelligence for novel analyses. Furthermore, incorporation of digital pathology into environmental monitoring studies using standardized bioindicator species or groups such as bivalves and fish can greatly improve the accuracy, reproducibility, and efficiency of the studies. This review aims to introduce readers to digital pathology and how it can be applied to environmental studies. This includes guidelines for sample preparation, potential sources of error, and comparisons to traditional histopathological analyses.

Spatial and temporal variation of microplastic in mussels from intertidal and subtidal banks in the Southwestern Atlantic Ocean

The objective of this study was to identify the presence of MPs in M. platensis tissues and evaluate the spatial and temporal variation of MPs in this species between different zones (Intertidal and Subtidal) and years (2012 and 2019) in Buenos Aires province Villa Gesell, Southwestern Atlantic Ocean. Our hypothesis is that the Intertidal zone will have a greater number of MPs than the Subtidal zone, and this trend will also be observed in 2019 compared to 2012. Specimens of M. platensis from the intertidal zone were hand-collected during low tide on the pier pilings in August 2012 and 2019, and the subtidal specimens were obtained by bottom trawling from a campaign with the Oceanographic ship ARA Puerto Deseado in August 2012. In general, the number of MPs varied between zones, indicating a greater number of this contaminant in the intertidal zone, whereas the same was not observed for the years. Furthermore, among the analyzed specimens, 90 % contained MPs, all of which were in the form of fibers, with blue fibers being the predominant type, and polystyrene being the most prevalent polymer. This group of organisms has significant ecological roles and commercial value. Assessing their contamination status and MPs characteristics is important to understand the potential risks to marine ecosystems and human health.

Effects of the Interaction of Salinity and Rare Earth Elements on the Health of Mytilus galloprovincialis: The Case of Praseodymium and Europium

The growing use of products containing rare earth elements (REEs) may lead to higher environmental emissions of these elements, which can potentially enter aquatic systems. Praseodymium (Pr) and europium (Eu) are widely used REEs with various applications. However, their ecotoxicological impacts remain largely unexplored, with poorly understood risks to wildlife. Moreover, organisms also face environmental stressors like salinity fluctuations, and the nature of the interaction between salinity variations and contaminants is not yet clear. Therefore, this study aimed to evaluate the influence of salinity shifts on the impacts of Pr and Eu on adult mussels and the sperm of the species Mytilus galloprovincialis after 28 days and 30 min of exposure, respectively. To do so, biochemical and histopathological alterations were evaluated in adults, while biochemical and physiological changes were analysed in sperm. Additionally, the Integrated Biological Index (IBR) was calculated to understand the overall impact of each treatment. The results showed that adult mussels were most affected when exposed to the combination of high salinity and each element, which altered the behaviour of defence mechanisms causing redox imbalance and cellular damage. On the other hand, sperm demonstrated sensitivity to specific REE-salinity combinations, particularly Pr at lower salinity and Eu at higher salinity. These specific treatments elicited changes in sperm motility and velocity: Pr 20 led to a higher production of O2- and a decrease in velocity, while Eu 40 resulted in reduced motility and an increase in irregular movement. At both lower and higher salinity levels, exposure to Eu caused similar sensitivities in adults and sperm, reflected by comparable IBR scores. In contrast, Pr exposure induced greater alterations in sperm than in adult mussels at lower salinity, whereas the reverse was observed at higher salinity. These findings suggest that reproductive success and population dynamics could be modulated by interactions between salinity levels and REE pollution, highlighting the need for further investigation into how REEs and environmental factors interact. This study offers valuable insights to inform policymakers about the potential risks of REE contamination, emphasising the importance of implementing environmental regulations and developing strategies to mitigate the impact of these pollutants.

Ocean acidification aggravates the toxicity of deltamethrin in Haliotis discus hannai: Insights from immune response, histopathology and physiological responses

Ocean acidification (OA) and other environmental factors can collectively affect marine organisms. Deltamethrin (DM), a type II pyrethroid insecticide, has been widely detected in coastal and estuarine areas, while little attention has been given to the combined effects of DM and OA. In this study, Haliotis discus hannai was exposed to three pH levels (8.1, 7.7 and 7.4) and three DM nominal concentrations (0 μg/L, 0.6 μg/L and 6 μg/L) for 14 and 28 days. The results indicated that experimental acidification and/or DM exposure led to impaired immune function and pathological damage. Additionally, acidified conditions and DM exposure induced oxidative stress, and gills are more sensitive than digestive glands. With increasing pCO2 and DM nominal concentrations, superoxide dismutase (SOD) activity decreased, whereas catalase (CAT) and glutathione S-transferase (GST) activities increased in the gills. Moreover, the expression levels of Toll-like receptor (TLR) pathway-related genes were upregulated after exposure. Integrated biomarker response (IBR) analysis proved that acidified conditions and/or DM detrimentally affected the overall fitness of H. discus hannai, and co-exposure to experimental acidification and DM was the most stressful condition. This study emphasizes the necessity of incorporating OA in future pollutant environmental assessments to better elucidate the risks of environmental disturbance.

Pathological and oxidative stress responses of Mytilus galloprovincialis to Vibrio mediterranei infection: An in vivo challenge

Since the identification of Vibrio mediterranei as a causative agent in mass mortalities of pen shells across the Mediterranean, elucidating its pathogenicity, virulence, and interactions with other bivalves has gained importance. While the cellular and immune responses of bivalves to various Vibrio species have been extensively studied, the infectious characteristics of this Vibrio species, particularly in the context of pen shell outbreaks, remain unclear for other bivalves. Therefore, to evaluate its pathogenicity, we investigated the histological and oxidative effects on the Mediterranean mussel (Mytilus galloprovincialis), a key species in aquaculture. Two distinct infection setups were established: one involving the inoculation of seawater with the bacterial isolate and another involving direct injection of the bacteria into the mussels. After a 24-h exposure period, histological evaluations were conducted on the mantle, gill, and digestive gland tissues of the mussels. Additionally, measurements of superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), and lipid peroxidation levels were performed in the gill and digestive gland tissues. Oxidative responses were significantly elevated in both infection setups compared to the control group, with the directly injected samples exhibiting the highest oxidative responses (p < 0.05). Histological findings indicated that tissue-specific responses to host-pathogen interactions were consistent under both infection conditions. Notable observations included intense hemocytic infiltration in tissues, epithelial hyperplasia, and vacuolization in the gills, as well as focal necrotic areas in the digestive gland. The findings of this study indicate that V. mediterranei, a relatively novel pathogen, can provoke significant acute immune responses and tissue-level reactions in M. galloprovincialis, a species that is both widely distributed and vital to the food chain. These insights into the potential susceptibility of mussels underscore the need for further comprehensive research and inform the development of effective management strategies.

Rare earth elements and warming: Implications for adult mussel health and sperm quality

The present study aimed to investigate the effects of europium (Eu) exposure (10 μg/L), warming (a 4 °C increase), and their combination on Mytilus galloprovincialis. Biochemical and histopathological changes in adult mussels were evaluated after a 28-day exposure period. Additionally, biochemical and physiological alterations in sperm were measured following a 30-min exposure period. The overall responses to each treatment were assessed using the Integrated Biological Response index version 2 (IBRv2). In adult mussels, warming elevated metabolism and activated glutathione S-transferases (GSTs), leading to redox imbalance and cellular damage. Europium exposure alone slightly enhanced metabolism and GSTs activity, resulting in cellular damage and histopathological injuries in digestive tubules. The combined exposure to Eu and warming was the most detrimental treatment for adults, as indicated by the highest IBRv2 value. This treatment slightly increased metabolism and uniquely elevated the activity of antioxidant enzymes, as well as GSTs and carboxylesterases. Despite these responses, they were inadequate to prevent redox imbalance, cellular damage, and histopathological injuries in digestive tubules and gills. Regarding sperm, warming reduced reactive oxygen species (ROS) production but raised lipid peroxidation levels. Sperm exposed to this treatment also increased their oxygen consumption and exhibited reduced velocity. The IBRv2 indicated that Eu was the most harmful treatment for sperm, significantly increasing ROS production and notably decreasing sperm velocity. When combined with warming, Eu elevated superoxide anion (O2-) production, lowered sperm velocity, and increased oxygen consumption. This study underscores the importance of investigating the effects of rare earth elements and their interaction with climate change-related factors.

Histopathology reveals environmental stress in dusky flounder Syacium papillosum of the Yucatan Peninsula continental shelf

The histological changes in the liver, kidney, spleen, and gills of Syacium papillosum from the continental shelf of the Yucatan Peninsula, Gulf of Mexico, and their statistical associations with environmental conditions and pollutants were assessed in 2010, 2011, and 2012. We evaluated the extension and severity of the lesions through a degree of tissue change (DTC), and, with the sum of the number of lesion types within each of their DTC stages, we determined the histological alteration index (HAI). The liver and kidney were the most affected organs, with HAI values > 100. Fish with the most severe damage were observed on the Campeche Bank and the Caribbean Sea, contrasting with those collected from the northern Yucatan continental shelf. The presence of foci cellular alteration and abundant melanomacrophage centers indicated that these flatfishes were chronically exposed to environmental stress factors. Redundancy analyses showed strong associations between HAI values and hydrocarbon and heavy metal concentrations in muscle. Our results provide evidence for the first time of a differential health condition of the Yucatan shelf through the histopathology shown in S. papillosum, establishing the baseline for future monitoring programs in the region.

Persistent organic pollutants and chlorpyrifos in tissues of a histotrophic viviparous species, the Southern Eagle Ray Myliobatis goodei

Elasmobranchs are good indicators of marine pollution as they accumulate pollutants from water and food, and occupy different trophic levels. Concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and chlorpyrifos were quantified in muscle, liver, gonads, gills, and brain in both sexes and maturity stages of the Southern Eagle Ray, Myliobatis goodei, captured in Argentine coastal waters. Moreover, possible histological alterations in the liver and gonads were analyzed. Pollutant concentrations were pervasive across all tissues, with PCBs > OCPs > chlorpyrifos. Elevated pollutant levels were notably found in the liver and gills. We identified thirty-six PCB congeners in tissues, with low-chlorine congeners prevailing. Among OCPs, ∑DDT and ∑endosulfan were predominant. Females exhibited higher pollutant levels in most tissues compared to males, except in the gonads, and adults generally displayed elevated pollutant levels. Histological analysis revealed the presence of atretic follicles and melanomacrophages (MM). Continuous monitoring of pollutant levels, alongside their effects on physiological and ecological traits, is imperative for effective management and conservation efforts.

Study of the Impact of the Parasitic Microalgae Coccomyxa parasitica on the Health of Bivalve Modiolus kurilensis

The invasion of bivalves by parasitic microalgae Coccomyxa is widespread and causes pathologies and dysfunctions of the organs, especially in the most valuable products: the mantle and the muscle. The pathogenesis of the disease remains completely unknown. In this study, based on a macroscopic examination of Modiolus kurilensis and microalgae count in each infected individual, four stages of disease development with characteristic pathognomonic symptoms were described. During the progression of the disease, the concentration of alkaline phosphatase, glucose, calcium, hemolytic and agglutinating activities, number of basophils, eosinophils, phagocytes, and cells with reactive oxygen species increased in the hemolymph, while number of agranulocytes, cells with lysosomes, dead hemocytes, total protein concentration, as well as the weight of mollusks decreased. In the nephridia and digestive gland, necrosis, invasion of Nematopsis sp., hemocyte infiltration, and fibrosis increased. The ratio of changed tubules and occurrence of granulocytomas increased in the digestive gland, while the base membrane, nephrocytes and concretions changed in the nephridia. This study helps establish the variability of these parameters under normal conditions and their alteration during the disease. Moreover, these findings can be used for veterinary monitoring of the state of bivalves in natural and aquaculture populations.

The odd couple: Caffeine and microplastics. Morphological and physiological changes in Mytilus galloprovincialis

In recent years, the presence of pharmaceuticals and microplastics (MPs) in aquatic ecosystems has raised concerns about their environmental impact. This study explores the combined effects of caffeine, a common pharmaceutical pollutant, and MPs on the marine mussel Mytilus galloprovincialis. Caffeine, at concentrations of 20.0 μg L-1, and MPs (1 mg L-1, 35-50 μm size range), was used to mimic real-world exposure scenarios. Two hundred M. galloprovincialis specimens were divided into four groups: caffeine, MPs, Mix (caffeine + MPs), and Control. After a two-week acclimation period, the mollusks were subjected to these pollutants in oxygen-aerated aquariums under controlled conditions for 14 days. Histopathological assessments were performed to evaluate gill morphology. Cellular volume regulation and digestive gland cell viability were also analyzed. Exposure to caffeine and MPs induced significant morphological changes in M. galloprovincialis gills, including cilia loss, ciliary disk damage, and cellular alterations. The chitinous rod supporting filaments also suffered damage, potentially due to MP interactions, leading to hemocyte infiltration and filament integrity compromise. Hemocytic aggregation suggested an inflammatory response to caffeine. In addition, viability assessments of digestive gland cells revealed potential damage to cell membranes and function, with impaired cell volume regulation, particularly in the Mix group, raising concerns about nutrient metabolism disruption and organ function compromise. These findings underscore the vulnerability of M. galloprovincialis to environmental pollutants and emphasize the need for monitoring and mitigation efforts. RESEARCH HIGHLIGHTS: The synergy of caffeine and microplastics (MPs) in aquatic ecosystems warrants investigation. MPs and caffeine could affect gill morphology of Mytilus galloprovincialis. Caffeine-exposed cells had lower viability than the control group in the NR retention test. MPs and mix-exposed cells struggled to recover their volume.

The role of warming in modulating neodymium effects on adults and sperm of Mytilus galloprovincialis

The use of rare earth elements (REEs) has been increasing and one of the most used is neodymium (Nd). Being an emergent contaminant, its negative impacts are poorly understood. Aquatic organisms are also threatened by climate change-related factors, as is the case of warming, which can change the effects of REEs. Thus, the impacts of Nd, warming, and the combination of both stressors were studied in adult mussels and sperm of the species Mytilus galloprovincialis, after an exposure period of 28 days (adults) and 30 min (sperm). The effects were evaluated through the analysis of biochemical and histopathological alterations in adults and biochemical and physiological responses given by sperm. The results showed that mussels only activated their biotransformation capacity when exposed to the stressors acting alone, which was insufficient to avoid lipid peroxidation. Furthermore, warming (alone and combined with Nd) also produces damage to proteins. The digestive gland was the most sensitive organ to Nd, presenting several histopathological alterations. In the case of sperm, all stressors induced lipid peroxidation, a higher oxygen demand, and a decrease in velocity, even if the sperm viability was maintained. It seems that warming influenced the effects of Nd to some extent. The present findings contribute significantly to the field of REEs environmental toxicology by offering valuable insights into the impacts of Nd on various biological levels of mussels. Additionally, within the context of climate change, this study sheds light on how temperature influences the effects of Nd. The obtained results indicate that both stressors can potentially compromise the overall health of mussel populations, thereby affecting other species reliant on them for food and habitat. Moreover, this study highlights impaired sperm health, which could adversely affect their reproductive capacity and ultimately lead to population decline.

Coping with current impacts: The case of Scyliorhinus canicula in the NW Mediterranean Sea and implications for human consumption

The small-spotted catshark (Scyliorhinus canicula) is a bottom-dwelling elasmobranch that represents the most discarded catch in terms of biomass in the Catalan coast (NW Mediterranean). Potential impacts affecting its population and food safety implications have been assessed in three localities along the Catalan coast. Distinct indicators were integrated, such as biological data, ingested anthropogenic items (plastic and cellulose-like items), parasitological indices, trace metal concentrations and histopathology using liver as target organ. Although high ingestion rates of fibres and levels of some heavy metals, they do not seem negatively affected by any major pathology nor by the current levels of pollutants. Small-scale differences among localities and depths were found and discussed. No zoonotic parasites were found. Encysted larvae of Grillotia adenoplusia and, above all, the levels of Hg found in the musculature, that are well over the European Commission limits, rise concerns regarding human consumption of S. canicula in this region.

Exploring the pathology of liver, kidney, muscle, and stomach of fledgling seabirds associated with plastic ingestion

There remain significant gaps in knowledge about 'sub-lethal' impacts of plastic ingestion, particularly chronic impacts on cells, tissues, or organs. Few studies have applied traditional animal health tools, such as histopathology, to assess physiological damage to wildlife, with fewer still providing information on the dosage or exposure to plastics needed to elicit negative effects. Our study seeks to investigate a common hypothesis in plastic pollution research; that an increasing plastics burden will have an impact on an animal's health, examining two wild species with high levels of environmental exposure to plastic through their diet. Here we assess the histopathology of the muscle, upper digestive tract, liver and kidney of two seabird species that are known to be commonly exposed to plastic, comparing exposed and non-exposed individuals. Fledgling seabirds showed histopathological evidence of cumulative pressures such as starvation, disease, and endoparasite burden. However, we observed no evidence of chronic harm that could be explicitly linked to the plastics. We found one case of haemorrhage, reaffirming that large/sharp plastic foreign bodies may cause acute physical damage. Given the numerous interacting pressures on the health of fledging seabirds, including exposure to plastic, this study highlights the need to scrutinise plastic-animal interactions and research though a One Health lens.

The EU Interreg Project "GEREMIA" on waste management for the improvement of port waters: results on monitoring the health status of fish as bioindicator

Highly anthropized areas as ports represent complex scenarios that require accurate monitoring plans aimed to address the environmental status. In this context, the activities of the EU Interreg Project "GEstione dei REflui per il MIglioramento delle Acque portuali (GEREMIA)" were focused on comparing sites differently affected by human presence, as the Port of Genoa and the natural area of the S'Ena Arrubia fishpond: a panel of analyses was carried out on Mugilidae fish sampled in these two areas, aimed to address trace metal accumulation in the liver, gills, and muscle, as well as cytochrome P450 (CYP450) induction in liver and biliary polycyclic aromatic hydrocarbon (PAH) metabolites, and histopathological alterations in the liver and gills. Chemical analyses in the liver, gills, and muscle of specimens collected in the port area showed an overall higher degree of trace metal contamination compared to the natural fishpond, and similar results were obtained in terms of CYP450 induction and biliary PAH metabolites, suggesting a higher exposure to organic compounds. In addition, histopathological analyses revealed a significant alteration and then a loss of functionality of liver and gill tissue in individuals from the port. Overall, this study describes the complex environmental pollution scenario in the Port of Genoa, confirming the importance of using multidisciplinary approaches and different types of analyses to address both the presence and the effects of contaminants in marine environments.

Multipathogen infections and multifactorial pathogenesis involved in noble pen shell (Pinna nobilis) mass mortality events: Background and current pathologic approaches

Disease outbreaks in several ecologically or commercially important invertebrate marine species have been reported in recent years all over the world. Mass mortality events (MMEs) have affected the noble pen shell (Pinna nobilis), causing its near extinction. Our knowledge of the dynamics of diseases affecting this species is still unclear. Early studies investigating the causative etiological agent focused on a novel protozoan parasite, Haplosporidium pinnae, although further investigations suggested that concurrent polymicrobial infections could have been pivotal in some MMEs, even in the absence of H. pinnae. Indeed, moribund specimens collected during MMEs in Italy, Greece, and Spain demonstrated the presence of a bacteria from within the Mycobacterium simiae complex and, in some cases, species similar to Vibrio mediterranei. The diagnostic processes used for investigation of MMEs are still not standardized and require the expertise of veterinary and para-veterinary pathologists, who could simultaneously evaluate a variety of factors, from clinical signs to environmental conditions. Here, we review the available literature on mortality events in P. nobilis and discuss approaches to define MMEs in P. nobilis. The proposed consensus approach should form the basis for establishing a foundation for future studies aimed at preserving populations in the wild.

Use of the gonadal tissue of the sea urchin Paracentrotus lividus as a target for environmental contamination by trace metals

Many environmental monitoring works have been carried out using biomarkers as a tool to identify the effects of oil contamination on marine organisms; however, only a few studies have used sea urchin gonadal tissue for this purpose. Within this context, the present work aimed to understand the impact of an oil spill, proposing the use of sea urchin gonadal tissue as a biomarker for environmental contamination by trace metals in the species Paracentrotus lividus. Biometric analysis, quantification analyses of the elements Cd, Pb, Ni, Fe, Mn, Zn, and Cu, as well as histopathological evaluations were performed in gonads of P. lividus collected from an area affected by hydrocarbons, named as impacted shore (IS) and an area not affected, named reference shore (RS). The results showed that carapace diameter (DC), total wet weight (WW), and Cd concentrations in the gonads were significantly influenced by the interaction between the rocky shores of origin, the months of sampling, and by the sex of the individuals. Moreover, from July until September, the levels of Zn and Cd were significantly lower in male than in female gonads. In July (the month of the oil spill), the indexes of histopathological alterations (IHPA) of membrane dilation were significantly higher in individuals from the IS, compared to the individuals from the RS. In addition, there were significant correlations between biometric variables (wet weight, diameter of carapace, gonadal weight, and gonadosomatic index) and the elements Cd, Cu, Ni, and Mn concentrations. Lastly, a delay in the gametogenic cycle of the sea urchins from IS was also observed. Taken together, these findings suggest that direct exposure to trace metals induces histopathological lesions in P. lividus' gonads and affects its reproductive cycle.

Ability of Lactobacillus brevis 47f to Alleviate the Toxic Effects of Imidacloprid Low Concentration on the Histological Parameters and Cytokine Profile of Zebrafish (Danio rerio)

In the present article, the possible mitigation of the toxic effect of imidacloprid low-concentration chronic exposure on Danio rerio by the probiotic strain Lactobacillus brevis 47f (1 × 108 CFU/g) was examined. It was found that even sublethal concentration (2500 µg/L) could lead to the death of some fish during the 60-day chronic experiment. However, the use of Lactobacillus brevis 47f partially reduced the toxic effects, resulting in an increased survival rate and a significant reduction of morphohistological lesions in the intestines and kidneys of Danio rerio. The kidneys were found to be the most susceptible organ to toxic exposure, showing significant disturbances. Calculation of the histopathological index, measurement of morphometric parameters, and analysis of principal components revealed the most significant parameters affected by the combined action of imidacloprid and Lactobacillus brevis 47f. This effect of imidacloprid and the probiotic strain had a multidirectional influence on various pro/anti-inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-8). Therefore, the results suggest the possibility of further studying the probiotic strain Lactobacillus brevis 47f as a strain that reduces the toxic effects of xenobiotics. Additionally, the study established the possibility of using imidacloprid as a model toxicant to assess the detoxification ability of probiotics on the kidney and gastrointestinal tract of fish.

Marine Pollution and Advances in Biomonitoring in Cartagena Bay in the Colombian Caribbean

Coastal zones sustain extensive biodiversity, support key processes for ocean dynamics, and influence the balance of the global environment. They also provide resources and services to communities, determine their culture, and are the basis for their economic growth. Cartagena Bay in the Colombian Caribbean is the place of the establishment of one of the country's main cities, which has a great historical and tourist attraction, and it is also the location of the main commercial port and a great variety of industries. Historically, it has been affected by several environmental impacts and intense pollution. This situation has gained the attention of different researchers, so herein is presented a literature review with a systematic approach using RStudio's bibliometrix on the presence of pollutants and the impact on biodiversity in recent decades, providing a critical analysis of the state of Cartagena Bay and its future needs to ensure its recovery and conservation. In addition, the socioeconomic dynamics related to the environmental state of Cartagena Bay are presented from the framework drivers, pressures, status, impacts, and responses (DPSIR). The update and critical understanding of the sources, fate, and effects of pollution are important not only for the knowledge of the status of this singular ecosystem but also to encourage future research and entrench evidence to support decision makers' actions. This review highlights that several pollutants that have been detected exceeding sediment quality guidelines, like As, Cd, Hg, and PAH, are also reported to bioaccumulate and cause damage throughout the trophic levels of the coastal environment. In addition, the potential use of sentinel species and biomarkers for their monitoring is discussed. Finally, the factors that cause pollution and threaten the state of the bay continue to exert pressure and impact; thus, there is a call for the further monitoring of this ecosystem and the strengthening of policies and regulations.

Dual oxidative stress and fatty acid profile impacts in Paracentrotus lividus exposed to lambda-cyhalothrin: biochemical and histopathological responses

Lambda-cyhalothrin (λ-cyh) is a potential pyrethroid insecticide widely used in pest control. The presence of pyrethroids in the aquatic ecosystem may induce adverse effects on non-target organisms such as the sea urchin. This study was conducted to assess the toxic effects of λ-cyh on the fatty acid profiles, redox status, and histopathological aspects of Paracentrotus lividus gonads following exposure to three concentrations of λ-cyh (100, 250 and 500 µg/L) for 72 h. The results showed a significant decrease in saturated fatty acid (SFAs) with an increase in monounsaturated fatty acid (MUFAs) and polyunsaturated fatty acid (PUFAs) levels in λ-cyh treated sea urchins. The highest levels in PUFAs were recorded in the eicosapentaenoic acids (C20:5n-3), docosahexaenoic acids (C22:6n-3) and arachidonic acids (C20:4n-6) levels. The λ-cyh intoxication promoted oxidative stress with an increase in hydrogen peroxide (H2O2), malondialdehyde (MDA) and advanced oxidation protein products (AOPP) levels. Furthermore, the enzymatic activities and non-enzymatic antioxidants levels were enhanced in all exposed sea urchins, while the vitamin C levels were decreased in 100 and 500 µg/L treated groups. Our biochemical results have been confirmed by the histopathological observations. Collectively, our findings offered valuable insights into the importance of assessing fatty acids' profiles as a relevant tool in aquatic ecotoxicological studies.

Oxidative Stress and Immunopathological Alterations of Clarias gariepinus Exposed to Monocyclic Aromatic Hydrocarbons (BTX)

This study’s goal was to assess the catfish’s response to exposure to monoaromatic petroleum hydrocarbons (benzene, toluene, and xylene) and its recovery after exposure using oxidative stress, histopathological, and immunological changes as biomarkers. Four groups: one as control and other three exposed to benzene (0.762 ng/L), toluene (26.614 ng/L), and xylene (89.403 ng/L), respectively, for 30 days and then recovery period for 30 days. The levels of the cortisol, lipid peroxidation, and cytokines (IL-1β, IL-6) increased significantly (p < 0.05) after exposure to benzene and xylene compared to control. Superoxide dismutase (SOD), total antioxidant capacity (TAC), and acetylcholinstease (Ach) decreased significantly (p < 0.05) in fishes exposed to benzene only compared to control group. While glutathione-S-transferase (GST) did not show any change in different treatment groups compared to control group. The histopathological signs of liver exposed to benzene, toluene, and xylene displayed aggregation of melanomacrophages, congestion of sinusoids, vacuolar degeneration of hepatocytes, necrotic area with inflammatory cell infiltration, and thrombus of central vein. Kidney exposed to benzene, toluene, and xylene showed dilatation of Bowman’s space with atrophy of glomerular tuft, lyses of RBCs with mononuclear cell infiltration, multifocal area of hemopoietic tissue necrosis, organized thrombus with perivascular hemorrhage, focal inflammatory cellular reaction, renal tubular necrosis, and thrombus of blood vessels. Spleen exposed to benzene, toluene, and xylene showed hyperplasia of lymphoid follicles in white pulp in a mild degree. These lesions appeared to a mild degree or disappeared completely after recovery period to BTX except spleen. In conclusion, monocyclic aromatic hydrocarbons (BTX) are hazardous to fish and the toxicity level was as benzene > xylene > toluene even though after recovery period.

Histopathological alterations in the gonads of wild white clams Dosinia ponderosa inhabiting a former copper mine locality in the Gulf of California

OBJECTIVE

Prolonged exposure to heavy metals, such as Pb, Hg, or Cu, has multiple adverse effects on marine organisms at the cellular, physiological, and population levels. Bivalves' histopathology provides a sensitive biomarker of pollutant-induced stress and environmental health. Gonad tissue deterioration is of particular concern, as it affects the reproductive success of a species. This study aimed to examine the histopathological alterations caused by metal exposure in the gonad of the white clam Dosinia ponderosa.

METHODS

Organisms were sampled from three locations in the Gulf of California: Santa Rosalia (SR), a former Cu mining town; San Lucas beach (SL), a nearby site influenced by pollution; and Escondida beach (EB), which served as a control site. Histological and histochemical stains were used, and the prevalence and intensity level of each alteration were calculated.

RESULT

The prevalence of alterations was higher in the ovaries of SR clams (92% compared to 60% in SL clams and 32.7% in EB clams), during spawning (91.4% compared to 20% in SL clams and 4.7% in EB clams), and in winter (93.5% compared to 30% in SL clams and 17.4% in EB clams).

CONCLUSION

These findings suggest a significant deterioration in the gonads of white clams from SR, probably linked to the chronic exposure to high concentrations of Cu and possibly other heavy metals; hence, the reproductive health of the clams is likely compromised.

Concentration of polycyclic aromatic hydrocarbons (PAHs) and histological changes in Anomalocardia brasiliana and Crassostrea rhizophorae from Pernambuco, Brazil after the 2019 oil spill

The present study aimed to analyze the concentrations of polycyclic aromatic hydrocarbons (PAHs) in populations of the shellfish Anomalocardia brasiliana and oysters Crassostrea rhizophorae three years after the 2019 oil spill, as well as evaluate histopathological changes on the gill tissues of the bivalves. Individuals of both species were sampled at points along the northern and southern coast of Pernambuco, Brazil. The permanence of oil residues was confirmed, evidenced by the total concentration of PAHs in the shellfish from the northern coast, which was roughly four times higher than the southern one. Among the PAHs analyzed, the low molecular weight compounds naphthalene and anthracene were the main contributors to the total concentration. Histological changes in the gills of the bivalves, were more severe in the specimens sampled on the north coast indicating alterations in the bivalve's health, mainly on the state's northern coast.

Histological evaluations of organ tissues reveal sublethal effects in a freshwater mussel (Villosa iris) exposed to chloride and potassium concentrations below benchmark estimates

Salinization of freshwater ecosystems due to anthropogenic sources will increasingly impact biodiversity. An example of point-source industrial salinization has occurred from historical activities at a U.S. Environmental Protection Agency Superfund Site near Saltville, Virginia USA and its associated chemical waste ponds adjacent to the North Fork Holston River. These point source discharges are documented contributors to mussel declines, partially due to high concentrations of chloride (Cl^-, ≤ 26,000 mg Cl^-/L) and potassium (K⁺, ≤ 97 mg K⁺/L). During a chronic 61-day laboratory study, Rainbow mussels, Villosa iris, were exposed to concentrations of Cl- (0, 416, 831, and 1,663 mg/L) and K+ (0, 4, 8, and 17 mg/L) to determine effects on survival and organ tissues. All test mussels died by day-2 in the 1,663 mg Cl^-/L exposure, and 50% of mussels died by day-13 in the 17 mg K⁺/L concentration. Significantly greater abundances of tissue abnormalities were observed in digestive glands and kidneys with exposures to the 4 and 8 mg/L concentrations of K⁺ versus the control, and significantly greater abundances of lesions in kidneys were observed in the 416 and 831 mg Cl^-/L concentrations compared to the control. The sublethal effects to digestive glands and kidneys were below reported effect (EC_{50, 20, 10} and LOEC) concentrations. Significant histological differences between control and baseline (day-0 sample) mussels were observed, suggesting the need for further study on the effects of captivity during longer-term laboratory experiments.

Spatiotemporal patterns in the prevalence of microscopic hepatic changes in Gulf of Mexico Tilefish (Lopholatilus chamaeleonticeps) and associations with hepatic PAHs

Following the 2010 Deepwater Horizon blowout, demersal longline surveys were conducted across the Gulf of Mexico (GoM) continental shelf to evaluate polycyclic aromatic hydrocarbon (PAH) exposure, tissue accumulation, and health indices in demersal fishes. Tilefish (Lopholatilus chamaeleonticeps), a target species due to Gulf-wide distribution with documented high exposure to PAHs, were collected in the north central GoM at repeat stations 2012 to 2015, and from the northwest GoM, Bay of Campeche, and Yucatán Shelf in 2015 and 2016. Liver samples (n = 239) were analyzed for microscopic hepatic changes (MHCs) by a board-certified veterinary pathologist. Histological analyzes identified 14 MHCs. Prevalence of MHCs was generally uniform throughout the GoM, except for low prevalence on the Yucatán Shelf. Inflammatory and vacuolar changes were most prevalent, while pre-neoplasia and neoplasia were rare. Tilefish sampled annually in the north central GoM showed increases in inflammatory MHCs and glycogen-type vacuolar change over time, while lipid-type vacuolar change decreased over time. Short-term exposure to PAHs was assessed by measuring PAH metabolites in bile (n = 100) using high performance liquid chromatography with fluorescence detection. Longer-term accumulation of PAHs in tissue was assessed by analyzing liver (n = 111) for PAHs and alkylated homologs using QuEChERS extractions and gas chromatography tandem mass spectrometry. Six MHCs including glycogen-type vacuolar change, biliary fibrosis, foci of cellular alteration, parasites, hepatocellular atrophy, and necrosis were significantly associated with hepatic PAH accumulation in Tilefish from the northern central GoM; however, no MHCs were associated with biliary PAH metabolites. Combined with previous studies of PAH exposure and health indices in north central GoM Tilefish post-Deepwater Horizon, which also identified decreases in hepatic lipid storage and Fulton's condition factor that were correlated to increasing PAH exposure, these data indicate concerning temporal trends and changes in hepatic energy storage.

Evaluation of lead exposition length on the liver and intestinal histoarchitecture of eared dove (Zenaida auriculata)

Lead (Pb) is a metal that can produces irreversible damage in living organisms. Some studies had reported that Pb produces histophysiological alterations in the digestive system (mainly liver) of birds; however, the effect of this metal on small intestine has not been fully examined. Additionally, little information is available on Pb disturbances in native birds of South America. The present study aimed to evaluate the effect of different Pb exposure times on blood δ-aminolevulinic acid dehydratase (δ-ALAD) activity and on the histological and morphometric characteristics of the digestive system (liver and proximal intestine) of eared doves (Zenaida auriculata). A decrease of the blood δ-ALAD activity, dilatation of blood vessels and leukocyte infiltrates in intestinal submucosa and muscular layers, and reduction of the enterocyte nuclear diameter and Lieberkühn crypts area were observed. In liver were noted steatosis, proliferation of bile ducts, dilated sinusoids, leukocyte infiltrates, and melanomacrophage centers. The portal tract area and the thickness of the portal vein wall were increased. In conclusion, the results showed that Pb produces histological and morphometric alterations on the liver and small intestine according to the exposure time, which should be considered when the dangerousness of environmental pollutants is evaluated in wild animals.

Revealing the capability of the European hake to cope with micro-litter environmental exposure and its inferred potential health impact in the NW Mediterranean Sea

Prevalence, abundance, concentration, size and composition of anthropogenic items (AIs) (synthetic and non-synthetic) ingested by Merluccius merluccius juvenile specimens and from near-bottom water samples from different localities off the Catalan coast (NW Mediterranean), were characterized. The potential effect of AIs on fish condition was assessed through different health indicators. Virtually all AIs found in fish and near-bottom water samples were fibres. A mean of 0.85 fibres/m³ from the surrounding water was observed. Fish ingested a mean of 1.39 (SD = 1.39) items/individual. Cellulosic fibres were predominant (77.8% of samples), except for Barcelona. No differences in ingested AIs abundance and composition off Barcelona between 2007 and 2019 were found. Small AIs from the environment matched ingested AIs composition. Hakes did not ingest large fibres despite being present in the environment, probably due to their feeding behaviour. No adverse health effects or parasites aggregations were detected to be potentially related to AIs ingestion.

Mitigating the nephrotoxic impact of hexavalent chromium in Ctenopharyngodon idellus (grass carp) with Boerhavia diffusa (punarnava) leaf extract

In Ctenopharyngodon idellus, the ameliorative influence of rutin-containing leaf extract of Boerhavia diffusa was assessed against chronic exposure to hexavalent chromium. For this, alterations in chromium accumulation, oxidative stress, kidney function markers, histopathology (light and transmission electron microscopy), and transcriptional profiling (Nrf2 and MT2) were examined. RP-HPLC analysis confirmed the presence of rutin (90.45 ± 0.98 mg/g) in the ethanolic leaf extract of the plant. LD₅₀ of the extract to the fish was beyond 5000 mg/kg b.w. The fish was subjected to a sublethal concentration of hexavalent chromium (5.30 mg/L) accompanied by a dose of 250 mg/kg b.w./day of extract in the diet for the experimental duration of 45 days. The extract alone did not generate any adverse consequences in the nephric tissue. Chronic exposure to hexavalent chromium damaged tissue irreparably, demonstrated by elevated levels of kidney function markers (blood urea nitrogen and creatinine) and altered histoarchitecture (DTC value of 78.02 ± 10.5). The metal exposure increased chromium accumulation and malondialdehyde (MDA) and decreased the reduced glutathione (GSH) levels, the activity of antioxidant enzymes (superoxide dismutase, catalase and glutathione-S-transferase) and gene expression in the tissue. The co-supplementation of leaf extract with metal exposure revealed a tissue architecture with normal to slight modifications, and the level of kidney markers, antioxidants, and genes expressed in a normalized range. Principal component analysis created two components with antioxidants (GSH, SOD, CAT, and GST) revealing a negative correlation with the second component comprising MDA, DTC, and chromium concentration. It can be concluded that B. diffusa leaves are safe additives in the fish diet and possess an ameliorative capacity for renal injury incurred by hexavalent chromium.

Chronic hypoxia and Cu2+ exposure induce gill remodeling of largemouth bass through endoplasmic reticulum stress, mitochondrial damage and apoptosis

Hypoxia and Cu²⁺ pollution often occur simultaneously in aquatic ecosystems and jointly affect physiology of fish. As the respiratory and ion exchange tissue of fish, how gill responds to the stress induced by these two abiotic environmental factors is still unclear. We have conducted a study by exposing largemouth bass (Micropterus salmoides) to hypoxia (2.0 mg·L^-1) and/or Cu²⁺ (0.5 mg·L^-1) for 28 days to answer this question. We subsequently studied respiratory rate, Cu²⁺ transport, endoplasmic reticulum (ER) stress, mitochondrial damage, and morphology in gill tissue on day 7, 14, 21 and 28. We found that hypoxia exposure increased the respiratory rate of largemouth bass, reflecting the response of largemouth bass to cope with hypoxia. Of note, Cu²⁺ entered gill by specifically binding to CTR1 and its accumulation dramatically in gill disrupted the response of largemouth bass to hypoxia. Hypoxia and/or Cu²⁺ exposure led to ER stress and mitochondrial damage in gills of largemouth bass. ER stress and mitochondrial damage induced apoptosis by activating caspase-8 and caspase-9 signaling pathways, respectively. Apoptosis induced by hypoxia and Cu²⁺ exposure had a positive and synergistic effect on gill remodeling by reducing interlamellar cell masses. In addition, Cu²⁺ exposure induced hypoxia-like remodeling to gill morphology through mechanisms similar to hypoxia exposure. Most of gene expression changed mainly within 21 days and recovered to the control level on day 28, reflecting the acclimation of largemouth bass to hypoxia and/or Cu²⁺ exposure at gene expression level. Overall, our research suggests that chronic hypoxia and Cu²⁺ exposure could induce gill remodeling of largemouth bass through ER stress, mitochondrial damage and apoptosis. The outcomes could provide an insight for fish environmental adaptation and environmental toxicology.

Effects of an Endocrine Disruptor Triclosan on Ruditapes decussatus: Multimarker and Histological Approaches

The aim of this work was to study the ecotoxicological effects of an endocrine disruptor triclosan on the clam Ruditapes decussatus. The bivalves were exposed to three concentrations of this biocide (C1 = 100 ng/L, C2 = 200 ng/L and C3 = 500 ng/L) for three and seven days. The impact was assessed at the gills and digestive glands, through activities of an antioxidant defense biomarker (Gluthatione S-Transferase, GST), a damage biomarker (Malondialdehyde, MDA), and a neurotoxicity biomarker (Acetylcholinesterase, AChE). Furthermore, histological traits were approached in different organs to evaluate any possible alteration induced by triclosan. It appears from this study that both gills and digestive glands responded discernibly to triclosan and effects were concentration-dependent. The stressed clams showed a significant increase in their GST and MDA activities in gills and digestive glands compared to controls for both time slots considered. In turn, the AChE activity was clearly inhibited in both organs in a time dependent way. The histological study made it possible to observe several structural pathologies caused by triclosan in the gills and the digestive gland. These alterations consisted mainly of inflammatory reactions, malformations of the lamellae and fusion of the gill filaments, degeneration of the connective tissue, and the erosion of the gill cilia with the appearance of certain severe alterations (cell necrosis and apoptosis), which can thus cause a malfunction of the gills and eventually lead to a reduction in oxygen consumption and a disruption of the osmoregulation for bivalves. Alterations in the digestive gland have also been detected, mainly by epithelial alterations, thinning of the tubules, and alteration of the basal cell membrane which can impair the ability of clams to absorb food. At germinal cells, several damages were observed in the oocytes which probably disturbed the reproductive function and the fertility of the clams. The damages observed in female gonads were caused by the cytolysis of a large number of oocytes through autophagy and necrosis at 200 ng triclosan/L. Moreover, at 500 ng triclosan/L, hemocytic infiltration was observed in acini and apoptotic bodies reflected in the fragmentation of more than 90% of oocytes.

Morphological parameters of hepatocytes in the European mole (Talpa europaea) and herb field mouse (Sylvaemus uralensis) under industrial pollution: Qualitative and quantitative assessment

Morphological alterations of cells and tissues usually occur in biological organisms exposed to environmental contaminants, there by acting as a biomarker of environmental pollution, thus, making this study highly pertinent. The effect of industrial pollution on the qualitative and quantitative morphological parameters of hepatocytes (through histological analysis and cytomorphometry) was studied in two contrasting species of small mammals (Talpa europaea and Sylvaemus uralensis), taking into account the animal age (young and adult groups) and liver concentrations of heavy metals (Cu, Zn, Cd, Pb). Studies were performed in the regions exposed to emissions from two currently operating copper smelters: Middle Ural Copper Smelter (Middle Urals, T. europaea catching area) and Karabash Copper Smelter (Southern Urals, S. uralensis catching area). Seven morphometric parameters of hepatocytes were measured, of which two key parameters were selected by the method of principal components-the cell packing density and nuclear-cytoplasmic ratio (N/C). It was found that cell packing density in T. europaea from the impact zone decreased relative to the background area in young animals. At the same time, the differences in this parameter between the age groups from the background zone were leveled in the impact area of catching. The N/C ratio in T. europaea hepatocytes showed no correlation with either animal age or site of capture (background or impact area). In S. uralensis, both parameters, even taking into account the age, were found to be insensitive to indicate an effect of industrial pollution. Dystrophic changes (tested through histological analysis) in the liver tissue were revealed in all animal groups, but their frequency did not depend on any of the factors (age, zone) as well as the level of accumulation of toxic heavy metals (Cd, Pb). Morphometric parameters of hepatocytes have proved to be more reliable indicators of pollution, compared to the frequency of liver histopathology, due to lower subjectivity in their evaluation.

Elucidating the consequences of the co-exposure of microplastics jointly to other pollutants in bivalves: A review

The marine environment has numerous impacts related to anthropogenic activities including pollution. Abundances of microplastics (MPs) and other pollutants are continuously increasing in the marine environment, resulting in a complex mixture of contaminants affecting biota. In order to understand the consequences, a review of studies analyzing combined effects of MPs and other types of pollutants in bivalves has been conducted as species in this group have been considered as sentinel and bioindicators. Regarding studies reviewed, histological analyses give evidence that MPs can be located in the haemolymph, gills and gonads, as well as in digestive glands in the intestinal lumen, epithelium and tubules, demonstrating that the entire body of bivalves is affected by MPs. Moreover, DNA strand breaks represent the most relevant form of damage caused by the enhanced production of reactive oxygen species in response to MPs exposure. The role of MPs as vectors of pollutants and the ability of polymers to adsorb different compounds have also been considered in this review highlighting a high variability of results. In this sense, toxic impacts associated to MPs exposure were found to significantly increase with the co-presence of antibiotics or petroleum hydrocarbons amongst other pollutants. In addition, bioaccumulation processes of pollutants (PAHs, metals and others) have been affected by the co-presence with MPs. Histological, genetic and physiological alterations are the most reported damages, and the degree of harm seems to be correlated with the concentration and size of MP and with the type of pollutant.

Anthropogenic pollutants in Nephrops norvegicus (Linnaeus, 1758) from the NW Mediterranean Sea: Uptake assessment and potential impact on health

Anthropogenic pollution is considered one of the main threats to the marine environment, and there is an imperious need to assess its potential impact on ecologically and economically relevant species. This study characterises plastic ingestion and tissue levels of potentially toxic metallic elements in Nephrops norvegicus and their simultaneous levels in abiotic compartments from three locations of the Catalan coast (NW Mediterranean Sea). A multidisciplinary assessment of the health condition of N. norvegicus through condition indices, enzymatic biomarkers and histological techniques is provided, and its relationship with anthropogenic pollutant levels explored. Plastic fibres were commonly found in stomachs of N. norvegicus (85% of the individuals), with higher abundances (13 ± 21 fibres · ind^-1) in specimens captured close to Barcelona. The presence of long synthetic fibres in near-bottom waters, as well as the mirroring trends in abundance among locations for water and ingested plastics, suggest that uptake from water may be occurring potentially through suspension feeding. The spatial variability in the levels of metallic elements in N. norvegicus was poorly correlated to the variability in sediments. In any case, present levels in abdominal muscle are considered safe for human consumption. Levels of ingested plastics only showed significant, yet weak, correlations with glutathione S-transferase and catalase activities. However, no other health parameter analysed showed any trend potentially associated to anthropogenic pollutant levels. Neither the condition indices nor the histopathological assessment evidenced any signs of pathologic conditions affecting N. norvegicus. Thus, it was concluded that presently there is no evidence of a negative impact of the studied pollutants on the health condition of N. norvegicus in the studied grounds.

Assessment of the health status of the European anchovy (Engraulis encrasicolus) in the NW Mediterranean Sea from an interdisciplinary approach and implications for food safety

The European anchovy (Engraulis encrasicolus) is a small pelagic fish with an outstanding commercial value supporting important fisheries and is a key component of pelagic ecosystems in the Mediterranean Sea. Progressive reductions in the population size of this species has been observed in the Mediterranean Sea during recent decades, accompanied by a decline in the body condition, as well as the size/age of maturation. Nonetheless, the health status has not been yet assessed using a holistic approach. Herein, we analyse the health status of the European anchovy, integrating distinct indicators from fish condition, enzymatic biomarkers, presence of tissue alterations, and parasite descriptors. In addition, we analyse the presence of anthropogenic items (AIs) in the digestive tract of fish and their potential impact on health status. Additionally, we assess the differences between current AIs values and those recorded over 12 years ago. None of the health indicators studied provided evidence of relevant pathologic conditions affecting this fish species in the studied area. However, changes in the pattern of liver parenchyma were found. Compared with anchovy populations from other distribution areas, no zoonotic parasites were recorded in this study, demonstrating a reduced risks associated with foodborne transmission to humans. AIs, such as fibres and plastic particles, were found in the digestive tract of half of the fish analysed. A significant increase was detected in AIs prevalence between 2007 (40 %) and 2019 (70 %), alongside differences in the abundance and typology of the AIs, though this does not seem to have impacted fish health yet. Therefore, our work underscores the importance of implementing a regular program to monitor the health status of this key species to better understand population dynamics and their drivers.

Morphological and Functional Alterations Induced by Two Ecologically Relevant Concentrations of Lead on Danio rerio Gills

Lead (Pb), due to its high toxicity and bioaccumulation tendency, is one of the top three pollutants of concern for both humans and wildlife and occupies second place in the Priority List of Hazardous Substances. In freshwater fish, Pb is mainly absorbed through the gills, where the greatest accumulation occurs. Despite the crucial role of gills in several physiological functions such as gas exchange, water balance, and osmoregulation, no studies evaluated the effects of environmentally relevant concentrations of Pb on this organ, and existing literature only refers to high levels of exposure. Herein we investigated for the first time the molecular and morphological effects induced by two low and environmentally relevant concentrations of Pb (2.5 and 5 μg/L) on the gills of Danio rerio, a model species with a high translational value for human toxicity. It was demonstrated that Pb administration at even low doses induces osmoregulatory dysfunctions by affecting Na⁺/K⁺-ATPase and AQP3 expression. It was also shown that Pb upregulates MTs as a protective response to prevent cell damage. Modulation of SOD confirms that the production of reactive oxygen species is an important toxicity mechanism of Pb. Histological and morphometric analysis revealed conspicuous pathological changes, both dose- and time-dependent.

Univariate or multivariate approaches for histopathological biomarkers in the context of environmental quality assessments?

Although the simplification of multivariate histopathological data into univariate indices can be useful for the assessment of environmental quality, this implies a great loss of information. The objective of the present study was to evaluate the effectiveness, in the context of environmental quality assessment, of an approach that integrates individual histopathological responses in a discriminated manner with the results of contaminants by means of multivariate analyses. This analysis was compared to the diagnosis of environmental quality provided by the use of the univariate Bernet histopathological index. Contaminant loads (sediments and fish) and the liver histopathology of Cathorops spixii were integrated through multivariate analysis. Integrated individual histopathological responses allowed classifying environmental quality from more to less impacted sites, while the univariate index showed some inconsistencies with chemical loads and allowed identifying only the most impacted site.

Metabolic, cellular and defense responses to single and co-exposure to carbamazepine and methylmercury in Dreissena polymorpha

Carbamazepine (CBZ) and Hg are widespread and persistent micropollutants in aquatic environments. Both pollutants are known to trigger similar toxicity mechanisms, e.g. reactive oxygen species (ROS) production. Here, their effects were assessed in the zebra mussel Dreissena polymorpha, frequently used as a freshwater model in ecotoxicology and biomonitoring. Single and co-exposures to CBZ (3.9 μg L^-1) and MeHg (280 ng L^-1) were performed for 1 and 7 days. Metabolomics analyses evidenced that the co-exposure was the most disturbing after 7 days, reducing the amount of 25 metabolites involved in protein synthesis, energy metabolism, antioxidant response and osmoregulation, and significantly altering cells and organelles' structure supporting a reduction of functions of gills and digestive glands. CBZ alone after 7 days decreased the amount of α-aminobutyric acid and had a moderate effect on the structure of mitochondria in digestive glands. MeHg alone had no effect on mussels' metabolome, but caused a significant alteration of cells and organelles' structure in gills and digestive glands. Single exposures and the co-exposure increased antioxidant responses vs control in gills and digestive glands, without resulting in lipid peroxidation, suggesting an increased ROS production caused by both pollutants. Data globally supported that a higher number of hyperactive cells compensated cellular alterations in the digestive gland of mussels exposed to CBZ or MeHg alone, while CBZ + MeHg co-exposure overwhelmed this compensation after 7 days. Those effects were unpredictable based on cellular responses to CBZ and MeHg alone, highlighting the need to consider molecular toxicity pathways for a better anticipation of effects of pollutants in biota in complex environmental conditions.

Impacts of tailings of Fundão dam (Brazil) rupture on marine fish: Metals bioaccumulation and physiological responses

This study evaluated the impacts of the mining tailings after the rupture of the Fundão dam on fish communities on the Atlantic Ocean southeast coast. Four sample collections were carried out over two years (2018-2020), in seasonal periods. Omnivorous/herbivorous and carnivorous fish were collected for analysis of metal bioaccumulation, multibiomarkers of environmental contamination and histopathology. Metal bioaccumulation was stronger correlated in carnivorous fish in the dry-2018 collection, besides higher activity of antioxidant enzymes, energy metabolism and higher morphological damage; however, there was less oxidative damage and less metallothioneins induction, and these variables were strongly associated with the wet-2020 collection. In a temporal view, it was possible to observe a reduction in metal levels in fish, except in the mouth of the Doce River. These events can be explained by seasonal natural events, which tend the resuspension and boost metal levels, mainly in the mouth region during the rainy season.

Impact assessment of a large river on the sediments and fish from its continental shelf: using Solea solea as sentinel in the Ebro river mouth (NW Mediterranean, Spain)

Many studies have been carried out along mighty rivers with heavily industrialized watersheds to evaluate pollutants and their effects on freshwater organisms. However, their impact on marine organisms is virtually unknown. In order to cover this gap, Solea solea, one of the most important commercial fish species, together with sediments, were sampled during 2013-2015 offshore from the Ebro Delta river mouth. Fish health indicators (condition indices, histological tissue alterations, and parasite descriptors) were used to assess the potential effect of pollutants, an issue of particular interest in the area following the dredging activities taking place in the river upstream in 2013. No major histopathological alterations were detected, but perivascular inflammatory foci (PIF) were frequently observed, especially in 2014. The most prevalent and abundant parasites were acanthocephalans and digeneans within the digestive tract and copepods on the gills. Levels of trace metals from sediments and fish muscle were below the effects range median and reference levels accepted for human consumption, respectively. However, the lower levels of the hepatosomatic index, higher numbers of PIF, and variations in the abundance of parasites in 2014 and 2015 could suggest a pollutant exposure during these years. These results warn signs of toxicity, which could be associated with sediment leaks during the dredging activities.

Elasmobranchs as bioindicators of pollution in the marine environment

Bioindicator species are increasingly valuable in environmental pollution monitoring, and elasmobranch species include many suitable candidates for that role. By measuring contaminants and employing biomarkers of effect in relevant elasmobranch species, scientists may gain important insights about the impacts of pollution in marine ecosystems. This review compiles biomarkers applied in elasmobranchs to assess the effect of pollutants (e.g., metals, persistent organic pollutants, and plastics), and the environmental changes induced by anthropogenic activities (e.g., shifts in marine temperature, pH, and oxygenation). Over 30 biomarkers measured in more than 12 species were examined, including biotransformation biomarkers (e.g., cytochrome P450 1A), oxidative stress-related biomarkers (e.g., superoxide anion, lipid peroxidation, catalase, and vitamins), stress proteins (e.g., heat shock protein 70), reproductive and endocrine biomarkers (e.g., vitellogenin), osmoregulation biomarkers (e.g., trimethylamine N-oxide, Na⁺/K⁺-ATPase, and plasma ions), energetic and neurotoxic biomarkers (e.g., lactate dehydrogenase, lactate, and cholinesterases), and histopathological and morphologic biomarkers (e.g., tissue lesions and gross indices).

Biomarkers for pollution in caged mussels from three reservoirs in Bulgaria: A pilot study

The mussel-watch concept was firstly proposed in 1975, which was later adopted by several international monitoring programs worldwide. However, for the very first time, a field experiment with caged mussels was performed in three reservoirs in Bulgaria to follow the harmful effects of sub-chronic pollution (30 days) of metals, trace, and macro-elements, as well as some organic toxicants, such as polybrominated diphenyl ethers and chlorinated paraffins. Therefore, we studied the biometric indices, histochemical lesions in the gills, biochemical changes in the digestive glands (antioxidant defense enzymes, such as catalase, glutathione reductase, and glutathione peroxidase; metabolic enzymes, such as lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase, and the neurotransmitter cholinesterase), in addition to the DNA damage in the Chinese pond mussel, Sinanodonta woodiana (Lea, 1834) in Kardzhali, Studen Kladenets and Zhrebchevo reservoirs in Bulgaria. Significant correlation trends between the pollution levels, which we reported before, and the biomarker responses were established in the current paper. Overall, we found that both tested organs were susceptible to pollution-induced oxidative stress. The different alterations in the selected biomarkers in the caged mussels compared to the reference group were linked to the different kinds and levels of water pollution in the reservoirs, and also to the simultaneously conducted bioaccumulation studies.

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The effects of water pollution in caged mussels from three large dam reservoirs in Bulgaria were assessed.

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A cocktail of different inorganic and organic toxicants was measured both in waters and mussels for the first time.

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Different biomarker responses (cellular to individual) were also followed in gills and digestive glands of the transplants.

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Correlation trends between the pollution levels and the applied biological tools were established.

Histopathological alterations induced by marine environmental pollutants on the bivalve Cerastoderma glaucum (Bruguière 1789) from Temsah Lake, Suez Canal, Egypt

Bivalves are considered a main consumed matrix for coastal communities worldwide and classified as hyperaccumulators of pollutants. The present study aims to determine some micro-organisms, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and okadaic acid (OA) levels in Cerastoderma glaucum collected from Temsah Lake, Egypt, and their induction through histopathological damage and caspase-3 protein expression. During the autumn, it was found different types of biological and chemical pollutants, especially benzo[a]pyrene (BaP) that accumulated in C. glaucum soft tissues and exceeded the safety limit for shellfish consumption. Dioxin-like PCB3 was predominant in C. glaucum soft tissues during autumn, but the total levels of PCBs in these tissues have not exceeded the permissible limit. Chlorophyll-a (Chl. a), nutrient concentrations, and Prorocentrum lima dinoflagellates in the water significantly increased during autumn. High P. lima abundance was confirmed by high OA in the soft tissues during this season compared to the other seasons. The measured contaminants may render C. glaucum more susceptible to bacterial and fungal infections. The autumn season showed a significant increase in the colony-forming units (CFU). C. glaucum showed calcification abnormalities and adhering of abnormal brown organic material to the inner surface of the shell valves, which was related to poor water conditions and Vibrio infection. Damages or injuries on gills and digestive gland tissues indicated an impact of the pollutants on C. glaucum. Also, high expressions of caspase-3 were recorded in these tissues during all the seasons. So, C. glaucum cockles, collected from Temsah Lake, may induce serious diseases to consumers, especially when eaten raw or insufficient cooking.

Assessing integrated biomarkers of triplefin fish Forsterygion capito inhabiting contaminated marine water - A multivariate approach

The presence of multiple chemicals in aquatic ecosystems makes evaluation of their real impact on the biota difficult. Integrated biomarkers are therefore needed to evaluate how these chemicals contribute to environmental degradation. The aims of the present study were to evaluate responses to and effects of marine pollution using a series of biomarkers through multivariate analyses. Transcriptional responses of cyp1a (cytochrome P450), mt (metallothionein), vtg (vitellogenin) and cyp19b (cytochrome P450 aromatase); branchial and hepatic histological alterations; and Fulton condition factors (CF) were evaluated, as well as the metals and polycyclic aromatic hydrocarbons present in Forsterygion capito in Auckland, New Zealand. Sites were selected along a contamination gradient: four highly contaminated sites and four less contaminated. Molecular responses with a higher relative expression of the mt and cyp1a genes were detected at a highly contaminated site (Panmure). Several histological lesion types were found in the livers of fish inhabiting both types of sites, but gill lesions were present primarily at highly contaminated sites. In terms of general health status, the lowest CF values were overwhelmingly found in fish from the same site (Panmure). The multivariate approach revealed that telangiectasia and hyperplasia were associated with the presence of chemicals, and these showed negative associations with the CF values, with fish from three highly contaminated sites being most affected. In conclusion, the multivariate approach helped to integrate these biological markers in this blennioid fish, thus providing a more holistic view of the complex chemical mixtures involved. Future studies should implement these analyses.

Histopathological evaluation of bivalves from the southwest coast of India as an indicator of environmental quality

Bivalve molluscs have been regarded as excellent bioindicators of environmental pollution as they persistently accumulate toxic contaminants present in their ecosystem. Histological alterations in the digestive gland and gills of three bivalve sp., Viz. edible oyster (Magallana bilineata), green mussel (Perna viridis) and black clam (Villorita cyprinoides) from ecologically sensitive regions of international significance on the southwest coast of India were evaluated using a semi-quantitative histopathological index to assess the environmental quality. The prominent tissue alterations included tubular vacuolation, haemocytic infiltration, parasitosis, lamellar disorganization, and the presence of prokaryotic inclusions.  The presence of ten trace metals was also evaluated in the digestive gland of bivalves. The histopathological indices were evaluated season-wise and region-wise. Seasonal variation in all the reaction patterns was observed in the digestive gland across sampling zones, with the highest indices observed during post-monsoon. The indices for all the reaction patterns in the digestive gland were significantly higher in bivalves from Vembanad Lake (Z4), followed by Periyar River (Z5). The indices for cellular changes and parasitosis in gills were the highest in the Ashtamudi estuary (Z1) and Z5, respectively. The global histopathological indices of the digestive gland and gills were also the highest in Z4, followed by Z5. Principal component analysis revealed that Z4 was distinct with the highest metal pollution index. A positive relation was observed with heavy metals, digestive gland histological alterations, and season and region of sampling.

Effects of sizes and concentrations of different types of microplastics on bioaccumulation and lethality rate in the green mussel, Perna viridis

Microplastics (MPs) can be defined as small pieces of plastics that are less than five millimetres in diameter. MPs can be consumed and may be accumulated by filter-feeding organisms such as mussels. Therefore, this study aimed to determine the acute effects of different types, sizes and concentrations of artificially synthesized MPs on the mortality rate and MP accumulation of the green mussel Perna viridis. The samples were exposed to 66, 333, 666, and 1333 items/L of small MPs (<30 μm), medium MPs (30-300 μm), and large MPs (300-1000 μm) polystyrene (PS), polypropylene (PP), and polybutylene succinate (PBS) for 96 h. MPs accumulation in the soft tissue of mussels and mortality effects from MPs ingestion were assessed. There was no mortality observed in the control group. Small PP particles can lead to more mortality than PS and PBS particles of the same size. However, medium- and large PS caused a higher mortality percentage than the same size particles of PP and PBS. Large PS, PP, and PBS showed higher mortality potential than other sizes. MPs largely accumulated in the soft tissues rather than in gill tissues following the 96-hour exposure period. Increased accumulation of the three types of MPs was accompanied by an increase in the percentage of mussel mortality. The study highlights how particle size and type are key factors in plastic particulate toxicity.

Chromium Exposure Causes Structural Aberrations of Erythrocytes, Gills, Liver, Kidney, and Genetic Damage in Striped Catfish Pangasianodon hypophthalmus

Heavy metal pollution due to anthropogenic activities poses a great threat to aquatic organisms. The present study was conducted to evaluate the cytotoxic and genotoxic effects of hexavalent chromium (potassium dichromate) on hemato-biochemical, histo-pathological, and genetical changes in striped catfish Pangasianodon hypophthalmus. Three sub-lethal doses (0.8, 1.6, and 3.2 mg/L) of chromium (Cr) were selected and fish were exposed in vivo contrasting with a control (0 mg/L) for 30 days. The study revealed that various hemato-biochemical parameters showed a significant decrease in hemoglobin (Hb), red blood cells (RBCs), and blood glucose content, whereas white blood cells (WBCs) significantly increased in Cr exposed fish. Frequencies of all forms of structural abnormalities of erythrocytes (erythrocytic cellular abnormalities; ECA, erythrocytic nuclear abnormalities; ENA and erythroblasts; Ebs) were significantly increased in higher two test concentrations (1.6 and 3.2 mg/L) when compared to control. Differential leucocyte count exhibited significant increase in neutrophil and decrease in lymphocytes in the highest Cr treated group. The severity of various histo-pathological changes in the gills, liver, and kidney were increased considerably with the increase of Cr concentrations. Similarly, the amount of DNA (ng/μl) decreased significantly in blood and tissues of different vital organs where the liver showed the highest decline compared to control in a concentration-dependent manner. Taken altogether, P. hypophthalmus is susceptible to Cr and can be used as a bio-indicator to assess aquatic metal pollution.

Atresia of ovarian follicles in fishes, and implications and uses in aquaculture and fisheries

Atresia of ovarian follicles, that is the degenerative process of germ cells and their associated somatic cells, is a complex process involving apoptosis, autophagy and heterophagy. Follicular atresia is a normal component of fish oogenesis and it is observed throughout the ovarian cycle, although it is more frequent in regressing ovaries during the postspawning period. An increased occurrence of follicular atresia above physiological rates reduces fish fecundity and even causes reproductive failure in both wild and captive-reared fish stocks, and hence, this phenomenon has a wide range of implications in applied sciences such as fisheries and aquaculture. The present article reviews the available literature on both basic and applied traits of oocyte loss by atresia, including its morpho-physiological aspects and factors that cause a supraphysiological increase of follicular atresia. Finally, the review presents the use of early follicular atresia identification in the selection process of induced spawning in aquaculture and the implications of follicular atresia in fisheries management.