Evaluation of the Genotoxic and Histological Effects in Neotropical Fish Prochilodus Lacustris (Pisces, Prochilodontidae) in Conservation Area of the Brazilian Northeast.

Human activities significantly impact the aquatic biota in lacustrine environments, leading to negative environmental consequences. Due to this, this study was carried out to evaluate the genotoxic and histological biomarkers in the gills and kidneys of Prochilodus lacustris. The collection of fish and water was conducted in three distinct stations (S1, S2, S3) in an international protected area in northeast Brazil. The histological alterations index was used to assess changes in the gills and kidneys at a histological level. In addition, micronucleus and nuclear abnormalities tests were employed to examine damage to the genetic material. According to the frequency of Micronucleus, nuclear injuries, and the histopathology of gills and kidneys, it can be inferred that station S1 had the highest impact on the fish, causing significant harm. Based on our findings, the organisms residing in Lake Açu are adversely affected by the poor environmental conditions. This raises doubts about the effectiveness of the Protection Area by Humid Zone of International Interest in Northeast Brazil.

First assessment of Rare Earth Element organotropism in Solea solea in a coastal area: The West Gironde Mud Patch (France).

Few studies exist on concentration and internal distribution of Rare Earth Elements (REEs) in marine fishes. REEs organotropism was determined in common sole (Solea solea) from the West Gironde Mud Patch (WGMP; N-E Atlantic Coast, France). The highest ∑REEs concentrations occurred in liver (213 ± 49.9 µg kg-1 DW) and gills (119 ± 77.5 µg kg-1 DW) followed by kidneys (57.7 ± 25.5 µg kg-1 DW), whereas the lowest levels were in muscles (4.53 ± 1.36 µg kg-1 DW) of Solea solea. No significant age- or sex-related differences were observed. The organotropism varied among groups of REEs. Light and heavy REEs preferentially accumulated in liver and gills, respectively. All considered organs showed different normalized REEs patterns, suggesting differences in internal distribution processes between organs. Further work should address: (1) baseline levels worldwide, and (2) factors controlling uptake and organ-specific concentration of REEs.

Microplastic Pollution in the Gastrointestinal Tract and Gills of Some Teleost and Sturgeon Fish from the Caspian Sea, Northern Iran.

The increasing microplastic pollution in the marine environment has raised global concern. The main risk of microplastics in aquatic ecosystem is their bioaccumulation in aquatic organisms. A few studies have reported microplastic pollution in the digestive system of Caspian Sea fish species, but there is no research on sturgeon species, nor on fish gills. We investigated the occurrence of microplastics in the gastrointestinal tract (GIT) and gills of 62 specimens belonging to four species including three teleosts (Cyprinus carpio, Rutilus kutum, and Chelon aurata) and one sturgeon (Acipenser persicus, a valuable endangered species) from the Caspian Sea between January and March 2022. Fish tissues were removed, exposed for 24 h to 10% KOH, and then dried on filter paper. Particles were observed under a stereomicroscope and analyzed by Raman microspectrometry, scanning electron microscopy, and energy-dispersive spectroscopy. A total of 91 microplastics were detected in the GIT (average of 1.46 ± 1.17 items/individual) and 63 microplastics in the gills (average of 1.01 ± 0.62 items/individual). A significant correlation was not found between the number of microplastics found in both tissues and fish body length, body weight, GIT weight, and gill weight (p > 0.05), except between microplastics isolated from gills and gill weight in C. carpio (rs = 0.707, p = 0.022). The abundance of microplastics in fish followed the order of A. persicus > C. aurata > R. kutum > C. carpio. The microplastics were in the size range of 45 to 5000 µm, with particles of 300 to 1000 µm being the most prevalent; 74.68% of the particles were shaped like fibers, 30.53% were red, and 70.6% were composed of nylon polymer. Environ Toxicol Chem 2023;42:2453-2465. © 2023 SETAC.

Microplastics and heavy metals in shrimp Litopenaeus vannamei from the SAMARE lagoon, Gulf of California: Is it a case of combined MPs-Zn pollution in gills?

Microplastic (MPs) pollution studies in the coastal environment are increasing, as observed in the growing number of documents published yearly. However, studies regarding the combined effect of MPs and heavy metal (HMs) pollution are scarce, particularly in marine biota. Microplastics and HMs were investigated in the exoskeleton (EX), gills (GI), gastrointestinal tract (GT), and muscle (MU) of the shrimp Litopenaeus vannamei from the Santa María-La Reforma (SAMARE) lagoon, Mexico. Results showed that shrimp ingest mainly MPs of the fiber type (74.7%) and fragments (22.7%). The most frequent MP colors in the four tissues were transparent (61.4%-72.2%) and blue (3.2-36.4%) fibers. Microplastic abundance in the four tissues was 5.5 ± 0.5 MPs per individual. The predominant polymers found in most tissues were cotton and synthetic polyethylene-terephthalate (PET). Heavy metals exhibited wide variability depending on the tissue and metal; the highest Cu concentration in the GI was 138 ± 16 µg/g, while the highest Cd value was 0.40 ± 0.11 µg/g, Ni was 17.0 ± 8.3 µg/g, and Zn was 120 ± 18 µg/g in the GT. The relationship between MPs and HMs was significant and positive (p < 0.05) between MPs and Zn in the GI. This reveals a possible MPs-Zn interaction due to cotton and PET reactivity or is related to polymer manufacture. This study implies that an essential part of the world fisheries is a potential route for MPs and HMs. The problem is exacerbated due to the consumption of whole shrimp tissues consumed by humans. Considering Mexican shrimp consumption, and MPs in this study, the estimated intake was 594 MPs/capita/year. Future research requires MP monitoring in coastal lagoons that support wildlife and important fisheries and assess their effects combined with HMs.

Revealing the environmental pollution of two estuaries through histopathological biomarkers in five fishes from different trophic guilds of northeastern Brazil.

Estuaries in Brazil are mostly anthropically affected due to the discharge of industrial and domestic effluents. In two of them, the Santa Cruz Channel Estuary (ITAP) and Sirinhaém River Estuary (SIR), historically affected by mercury pollution and sugarcane industry in Northeast Brazil, we assessed environmental pollution using liver and gill histopathological biomarkers in fish from different trophic levels. Liver samples exhibited serious damages such as hepatic steatosis, necrosis, and infiltration. The gills showed moderate to severe changes, such as lifting of epithelial cells, lamellar aneurysm, and rupture of lamellar epithelium. Most of the changes in the liver and gills were reported for species Centropomus undecimalis and the Gobionellus stomatus, which were considered as good sentinels of pollution. The combination of biomarker methodologies was efficient in diagnosing the serious damage to the species, reinforcing the need for monitoring the health of the ecosystems evaluated.

Multiple responses of Mytilus galloprovincialis to plastic microfibers.

Plastic microfibers (MF) represent the major source of MF found in the environment, the majority made of polyester (PES). Marine bivalves, suspension feeders widespread in coastal areas subjected to higher anthropogenic input, can accumulate MF from the water column in their tissues. This raised some concern about their possible impact on bivalve health and potential transfer along the food chain. In this work, the effects of PES-MF on the mussel Mytilus galloprovincialis were investigated, utilizing MF obtained by cryo-milling of a fleece cover. Fiber characterization indicated the polymer composition as polyethylene terephthalate (PET); the size distribution was in a length range resembling that of MF released from textile washing, and including those that can be ingested by mussels. MF were first screened for short-term in vitro immune responses in mussel hemocytes. The effects of in vivo exposure (96 h, 10 and 100 µg/L, corresponding to about 150 and 1500 MF/mussel/L, respectively), were then evaluated. Data are presented on hemolymph immune biomarkers (Reactive Oxygen Species and nitric oxide production, lysozyme activity), and on antioxidant biomarkers (catalase and glutathione S-transferase) and histopathology in gills and digestive gland. Tissue MF accumulation was also evaluated. MF exposure stimulated extracellular immune responses both in vitro and in vivo, indicating induction of immune/inflammatory processes. In both tissues, stimulation of antioxidant enzyme activities, suggesting oxidative stress conditions, and histopathological changes were observed, with stronger effects often observed at lower concentration. Although mussel retained a very small fraction of MF, their accumulation was higher in the digestive gland than in gills, and in both tissues of mussels exposed to the lowest concentration. Selective accumulation of shorter MF was also observed, particularly in gills. Overall, the results demonstrate that at environmental exposure levels, PET-MF have a significant impact on mussel physiology, affecting multiple processes in different tissues.

DNA damage and oxidative stress in gill cells of Cnesterodon decemmaculatus exposed to pesticides by runoff source in an agricultural basin.

In our country, great concern exists about diffuse pollution cause by the great use of pesticides in rural environments. A thorough analysis is needed to generate information, know the real situation and thus, be able to make decisions with the purpose of reducing environmental pollution. In situ bioassays have been carried out using Cnesterodon decemmaculatus within limnocorrals located in a surface natural water system that receives rainfall excess flowing from an agricultural basin with a typical crop rotation, including corn, wheat and soy. Specimens were taken from the limnocorrals 72 h after a probed natural runoff event toward the water body, and the gill cells were used to evaluate the DNA damage (comet assay, CA), catalase enzyme activity (CAT), and lipid peroxidation (LPO). In addition, the physicochemical analysis of the water (pH, temperature) and the presence and concentration of pesticides were carried out. The results showed significant differences on DNA damage and oxidative stress on the gill cells of the exposed fish compared to controls, being the combination of the rain regime and the mixtures of pesticides used in corn and soy more toxic than in wheat. These results highlight the necessity to understand detrimental processes caused by pesticides used in extensive systems of primary production, in order to prevent and minimize diffuse contamination, contributing to environmental recovery and sustainability.

Genomic and Environmental Factors Shape the Active Gill Bacterial Community of an Amazonian Teleost Holobiont.

Fish bacterial communities provide functions critical for their host's survival in contrasting environments. These communities are sensitive to environmental-specific factors (i.e., physicochemical parameters, bacterioplankton), and host-specific factors (i.e., host genetic background). The relative contribution of these factors shaping Amazonian fish bacterial communities is largely unknown. Here, we investigated this topic by analyzing the gill bacterial communities of 240 wild flag cichlids (Mesonauta festivus) from 4 different populations (genetic clusters) distributed across 12 sites in 2 contrasting water types (ion-poor/acidic black water and ion-rich/circumneutral white water). Transcriptionally active gill bacterial communities were characterized by a 16S rRNA metabarcoding approach carried on RNA extractions. They were analyzed using comprehensive data sets from the hosts genetic background (Genotyping-By-Sequencing), the bacterioplankton (16S rRNA) and a set of 34 environmental parameters. Results show that the taxonomic structure of 16S rRNA gene transcripts libraries were significantly different between the 4 genetic clusters and also between the 2 water types. However, results suggest that the contribution of the host's genetic background was relatively weak in comparison to the environment-related factors in structuring the relative abundance of different active gill bacteria species. This finding was also confirmed by a mixed-effects modeling analysis, which indicated that the dissimilarity between the taxonomic structure of bacterioplanktonic communities possessed the best explicative power regarding the dissimilarity between gill bacterial communities' structure, while pairwise fixation indexes (FST) from the hosts' genetic data only had a weak explicative power. We discuss these results in terms of bacterial community assembly processes and flag cichlid fish ecology. IMPORTANCE Host-associated microbial communities respond to factors specific to the host physiology, genetic backgrounds, and life history. However, these communities also show different degrees of sensitivity to environment-dependent factors, such as abiotic physico-chemical parameters and ecological interactions. The relative importance of host- versus environment-associated factors in shaping teleost bacterial communities is still understudied and is paramount for their conservation and aquaculture. Here, we studied the relative importance of host- and environment-associated factors structuring teleost bacterial communities using gill samples from a wild Amazonian teleost model (Mesonauta festivus) sampled in contrasting habitats along a 1500 km section of the Amazonian basin, thus ensuring high genetic diversity. Results showed that the contribution of the host's genetic background was weak compared to environment-related bacterioplanktonic communities in shaping gill bacterial assemblages, thereby suggesting that our understanding of teleost microbiome assembly could benefit from further studies focused on the ecological interplay between host-associated and free-living communities.

Cadmium and zinc accumulation and depuration in tilapia (Oreochromis niloticus) tissues following sub-lethal exposure.

Oreochromis niloticus was subjected to sub-lethal Cd and Zn concentrations for 14 days in order to evaluate their accumulation in the gills, liver, and muscle. Following that, the fish were placed to uncontaminated water for 7 days to allow the metals to be removed from the tissues. The gills had the highest bio-concentration factor for Cd and Zn. The gills showed the highest Cd accumulation rate, and the muscle showed the lowest. The muscle had the highest Cd depuration rate, while the liver had the lowest. The liver exhibited the highest Zn accumulation rate, while the gills and muscle had nearly similar values. Zn depuration rates were very consistent across all tissues.

Species, tissue and gender-related metal and element accumulation in fish species in a large reservoir (Turkey) and health risks and nutritional benefits for consumers.

Concentrations of 18 metals and elements (MEs) in the gills, skin, muscle and liver of Carasobarbus luteus and Cyprinus carpio from the Atatürk Reservoir in Turkey were investigated. The results revealed that variations in the ME contents between fish species can be attributed to different diets. The highest contents of most MEs were recorded in the gills. Gender had no significant effect on the contents of most MEs in the tissues of fish species investigated. The relations between MEs in tissues and fish size were not clear and consistent. Health risk assessment methods indicated that consumption of the studied fish species is safe. It was estimated that daily consumption of 140 g of C. carpio or 170 g of C. luteus would not be expected to cause any health risks. Furthermore, it was found that fish species would provide significant benefits in terms of intake of essential MEs.

Accumulation of microplastics in fish guts and gills from a large natural lake: Selective or non-selective?

In recent years, microplastics (MPs) have become emerging contaminant causing widespread concern about their ecotoxicological effects. However, little is known regarding the accumulation of MPs in different tissues of fishes, especially for freshwater fishes in natural environments. In this study, MPs in guts and gills of 11 fish species from Lake Chao, China were examined to explore the accumulation differences and foraging preferences of MPs. In general, MPs in fish guts varied from 2.85 to 8.38 items/individual, while ranged from 3.06 to 8.90 items/individual in fish gills. In terms of characteristic composition (shape, color, size, and polymer type), our results demonstrate higher occurrence of fibrous, black, small sized (<1 mm), and polypropylene MPs. Meanwhile, MPs concentrations in fish guts differed significantly among various feeding groups, with none significant difference detected in fish gills. In addition, fish guts exhibit more distinct foraging preferences for specific featured MPs in contrast with fish gills. These results indicate selective MPs accumulation in fish guts whereas random MPs accumulation in fish gills. Fish gills, adhering MPs by non-selective water exchange, may be more related to the real-time MPs abundance in water. To some extent, fish gills may be employed as important instruments to reflect MPs contamination in aquatic environments. Influenced by diverse feeding behaviors such as visual cues and sensory systems, MPs accumulation in fish guts reflect intrinsic differences, thus making fish guts sensitive organ in monitoring MPs' ecological risk for their health.

Evaluation of DNA Damage, Biomarkers of Oxidative Stress, and Status of Antioxidant Enzymes in Freshwater Fish (Labeo rohita) Exposed to Pyriproxyfen.

Pyriproxyfen (PPF) mimics a natural hormone in insects and disrupts their growth. It is a well-known synthetic insecticide and aromatic juvenile hormone analog frequently used in agriculture and vegetable crops to control various insect species. At present, scanty information is available about the possible potential threats of PPF in aquatic organisms. Therefore, in this study, different toxico-pathologic endpoints of PPF like DNA damage, biomarkers of oxidative stress, and status of antioxidant enzymes were determined in Labeo rohita (freshwater fish). In our study, 60 active, free from any external obvious ailments, same size, age, and body mass were randomly allocated to four glass aquaria (T0-T3) separately containing 100 L water. The fish present in groups T1, T2, and T3 were administered PPF dissolved in water 300, 600, and 900 µg/L for 30 days. Different tissues including the blood and visceral organs were obtained from each fish on days 10, 20, and 30 of the experiment. Results on various morphological and nuclear changes in red blood cells of PPF-exposed Labeo rohita fish including pear-shaped erythrocytes, spherocytes, red blood cells with a blebbed nucleus, micronucleus, and nuclear remnants were significantly increased. Our results on genotoxicity (comet assay) recorded significantly (P ≤ 0.05) increased DNA damage in various tissues of insecticide-exposed fish. The results on oxidative stress profile (reactive oxygen species and thiobarbituric acid reactive substances) and antioxidant enzymes (reduced glutathione superoxide dismutase, peroxidase, and catalase) in multiple tissues of Labeo rohita fish concluded significantly (P ≤ 0.05) higher quantity of biomarkers of oxidative stress and lower concentrations of different antioxidant enzymes in treated fish. Hence, the findings of our experimental research determine that PPF could induce adverse toxic impacts on multiple tissues of Labeo rohita fish.

Transepithelial potential remains indicative of major ion toxicity in rainbow trout (Oncorhynchus mykiss) after 4-day pre-exposure to major salts.

The Multi-Ion Toxicity (MIT) Model uses electrochemical theory to predict the transepithelial potential (TEP) across the gills as an index of major ion toxicity in freshwater animals. The goal is to determine environmental criteria that will be protective of aquatic organisms exposed to salt pollution. In recent studies, TEP disturbances above baseline (ΔTEP) during short-term exposures to major ions have been proven as indicative of their toxicity to fish, in accord with the MIT model. However, the acute 1-h exposures used in these previous studies might not be realistic relative to the 24 h or 96 h test periods used for toxicity assessment. To address this temporal inconsistency, the current study investigated both the TEP responses to serial concentrations of 10 major salts (NaCl, Na2SO4, NaHCO3, KCl, K2SO4, KHCO3, CaCl2, CaSO4, MgCl2, MgSO4) and plasma ion levels in juvenile rainbow trout after they had been pre-exposed to 50% of the 96h-LC50 levels of these same salts for 4 days. The pre-exposures caused no mortalities. In general, plasma ions (Na+, K+, Ca2+, Mg2+, Cl-) were well-regulated; however, pre-exposure to sulfate salts resulted in the greatest number of alterations in plasma ion levels. TEP responses remained largely similar to those of naïve trout (without salt pre-exposure). All salts caused hyperbolic concentration-dependent increases in TEP that were well-described by the Michaelis-Menten equation. In the pre-exposed trout, the variation of ∆TEP at the 96h-LC50 concentrations was only 2.2-fold, compared to nearly 28-fold variation among the molar concentrations of the various salts at the 96h-LC50s, identical to the conclusion for naïve trout. Overall, the results remove the temporal inconsistency of previous tests and remain supportive of the MIT model. In addition, the recorded alterations in certain plasma ions, baseline TEP, and Michaelis-Menten constants improve our knowledge on specific physiological responses after extended major ion exposure.

Microplastic occurrence in the gastrointestinal tract and gill of bioindicator fish species in the northeastern Mediterranean.

Microplastic pollution is an extremely emerging problem and its potential threats to the aquatic organisms were investigated worldwide. In this study, four different commercial fish species (Mullus barbatus (Linnaeus, 1758), Mullus surmuletus (Linnaeus, 1758), Mugil cephalus (Linnaeus, 1758), Saurida undosquamis (Richardson, 1848)) were used as a bioindicator to assess the microplastic pollution in the northeastern Mediterranean. The frequency of occurrence in the gastrointestinal tract (GIT) and gill was varied between 66-100% and 68-90%, respectively. The highest microplastic abundance was detected at the GIT of M. cephalus sampled from Asi River estuary. The majority of extracted microplastics were fiber, black in color and less than 1 mm in size. Fourier Transform Infrared Spectroscopy (FTIR) indicated the most common polymer type as polyethylene. This study is the first study examining the microplastic existence in gill and results obtained in this study improve the knowledge about the relationship of microplastic ingestion in fish and environmental conditions in the Northeastern Mediterranean Sea.

Accumulation of 25 elements in gills, liver, gonads, and muscle of European chub (Squalius cephalus), Cactus roach (Rutilus virgo), and pikeperch (Sander lucioperca) from Zlatar reservoir (Serbia).

Accumulation of Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, and Zn was analyzed in gills, liver, gonads, and muscle of European chub (Squalius cephalus), Cactus roach (Rutilus virgo), and pikeperch (Sander lucioperca) from Zlatar reservoir (Serbia) using inductively coupled plasma optical emission spectrometry (ICP-OES). The highest concentrations of Cu in liver as well as Ba, Ca, Fe, Mn, Na, P, and Sr in gills were detected in all fish species, while the lowest concentrations of Cu, Fe, Mn, Na, and Zn were detected in muscle. Pikeperch had significantly lower concentrations of Ba in all tissues compared to the other species, as well as Fe, P, and Sr in muscle, K, Mg, Mn, Sr, and Zn in gills, and Fe in gonads. European chub had significantly higher concentrations of Ca, Cu, and Zn in muscle, Cu in liver, and Cr and Cu in gonads compared to Cactus roach and pikeperch. Cd concentration in one individual of Cactus roach exceeded the maximum allowed concentration. The muscle was exposed to the lowest pressure of metal pollution in all species, and European chub accumulated more metals compared to the other species. There is no significant health risk due to consumption of investigated species. A major hazard index (HI) contributor in all species was Hg. According to the target carcinogenic risk factor (TR), target hazard quotient (THQ), and HI, men are under lower health risk compared to the women. The TR and THQ for As, Cr, Cu, Fe, Mn, Ni, and Zn as well as HI values were higher for European chub compared to the other species. On the other hand, THQ for Hg was highest for pikeperch.

Abundance and characteristics of microplastics in gastrointestinal tracts and gills of croaker fish (Johnius dussumieri) from off Mumbai coastal waters of India.

The present study was conducted to establish the intensity of microplastic pollution in demersal fish species, Johnius dussumieri, from the north eastern coastal waters of the Arabian sea. MP recovered were analysed for size, morphology, colour, and polymer type. The study results indicated that the GI tract and gills of individual fishes had 6.6 ± 1.7 and 6.2 ± 1.7 items, respectively. The microplastics having a size of <100 µm consisting of beads were found to be most predominant. Black and blue were the most present colours of microplastic in the tissues. Among the different studied months, a higher number of MP incidence was observed in the post monsoon period. There is no significant correlation observed between the microplastic numbers in gills and guts tissue. The present study shows that there is a potential risk of microplastic bioaccumulation in the fish body and subsequent risk to the consumers and organisms sharing the food chain.

Dietary Copper Requirements for Aquatic Animals: A Review.

Copper (Cu) is a vital microelement required for the optimum growth performance and wellbeing of aquatic animals. It contributed to various biological, physiological, and metabolic function in the entire body of the aquatic animals. Further, Cu is a cofactor for several enzymes involved in the antioxidation capacity and metalloenzyme formation. Some ingredients used for aquafeed formulation include sufficient amounts of Cu that can provide aquatic animals with their requirements. Nevertheless, in some cases, external Cu sources are needed to optimize the essential needs of aquatic animals. Inorganic, organic, and nano Cu forms are included in aquafeed and result in regulated physiological and biological functions. The addition of Cu should be added at particular doses considering the species, size, duration, and environmental conditions. Water-borne Cu level should also be considered as long as aquatic animals can obtain their requirements through gills to avoid overdosing and toxicity. Several studies reported the optimum doses of Cu required for optimal growth, productivity, and health status in several aquatic animals. This review article presents the up-to-date results of Cu-related studies in aquafeed. It also helps academia design further studies to better understand the border between Cu requirements and toxicity. Besides, planning for more studies involved in the understanding of the primary mode of action of Cu in aquatic animals' entire bodies.

METALLOTHIONEIN EXPRESSION IN A PARASITIC CRUSTACEAN, LAMPROGLENA CLARIAE (CRUSTACEA: COPEPODA), ON CLARIAS GARIEPINUS (TELOESTEI: CLARIIDAE) CORRESPONDS TO WATER QUALITY.

Globally, parasites are sensitive toward environmental changes, and, in some cases, they are even more sensitive than their hosts. However, there is limited knowledge on the physiological responses of parasites and their effects on their hosts in relation to environmental degradation. In this study, metallothioneins (MTs) were isolated and compared between the ectoparasite Lamproglena clariae and its host fish Clarias gariepinus. Differences in the levels of MTs in the parasite and host were compared to physicochemical water quality variables and metals to determine if MT expression was linked with changes in water quality. Clarias gariepinus individuals were sampled from 2 sites of differing water quality along the Vaal River using gill nets and assessed for L. clariae. Gill, muscle, and liver tissue of the host and L. clariae were collected and stored in liquid nitrogen for analysis of MT. Water and sediment samples were collected for metal analysis by inductively coupled plasma-optical emission spectrometry and inductively coupled plasma-mass spectrometry. Nutrient levels and water hardness in water samples were assessed using spectrophotometry. MTs were quantified using spectrophotometry and size exclusion chromatography in the host and parasite, respectively. Infections by L. clariae differed between sites, with higher parasite intensity at the unpolluted Vaal Dam site. Concentrations of MT in host tissues and L. clariae were significantly higher at the polluted site, below the Vaal River Barrage, compared to the Vaal Dam site. Parasite MT concentrations were significantly lower compared to concentrations in the liver and gill tissue of C. gariepinus individuals. In conclusion, differences in the concentrations of MT and infection biology of L. clariae reflected the state of the environment and support the usefulness of this parasite and other Lamproglena spp. as bioindicators.

Plastic in digestive tracts and gills of cod and herring from the Baltic Sea.

Plastic litter is widespread on our planet and is recognized as a contaminant of high concern. Plastic ingestion and retention in gills were studied in two key Baltic fish species: herring (Clupea harengus L.) and cod (Gadus morhua L.). In total, 183 fish from the southern Baltic Sea were analysed. Plastic litter was found in digestive tracts of 12.7 and 14.8% of herrings and cods, respectively. In addition, gills were shown to constitute an important transfer route of plastic to cod (9.9% of cods) but not to herring thus likely reflecting species-specific differences in fish lifestyles and/or water filtering capacity. No more than one plastic item per individual was found except for three fish with two items in their stomachs. Dominant microplastics (<5 mm) (MPs) (88.6% of all items) composed of irregular fragments, fibres and foils (61.3%, 25.8% and 12.9% of all MPs, respectively) were followed by meso- (5-25 mm) and macro-plastics (>25 mm) (5.7% each of all items). Plastic ingestion and retention in gills did not affect fish body condition assessed by Fulton's K index, although herrings that ingested plastic particles beyond the microplastic size range (i.e. >5 mm) were characterized by the lowest condition indices. All plastic items recovered from fish exhibited clear signs of weathering and surface extended due to their roughness and fragmentation which may enhance both sorption properties for chemical compounds and/or their leaching. Nevertheless, chemical contaminant levels in herring muscles were not different than in a plastic-free group. The vast majority of fibres found in fish was identified as air-borne or procedural contamination and were excluded from further analyses. In addition, the vessel's paint dust found in fish stressed the need for strict quality assurance also during fish sampling.

Ecotoxicity in Hyriopsis bialatus of copper and zinc biocides used in metal-based antifouling paints.

Biofouling is a costly burden for the shipping industry. Metal-based antifouling paints are widely used to protect submerged surfaces, but the release of metals from coatings and the recoating of hulls can leach large amounts of copper and zinc into aquatic environments, posing a risk for aquatic ecosystems and biodiversity. With this study, we studied the time-course metal accumulation and oxidative stress in the digestive gland and the gills of Hyriopsis bialatus, an Asian freshwater mussel, exposed to sublethal concentrations of cuprous chloride (50 and 5 µg/L) and zinc sulfate (1000 and 100 µg/L). Time-dependent accumulation was observed after exposure to copper, but zinc uptake was negligible. Integrated biomarker response (IBRv2) and statistical analysis of individual biomarker levels showed a greater biomarker response in the digestive gland and the gills after exposure to the higher concentration of CuCl and ZnSO4. Both compounds elicited a biochemical response, especially in the digestive gland. Glutathione peroxidase activity was increased after exposure to both metals at both concentrations, suggesting a powerful defense against lipid peroxidation. The biological impact of zinc was less than that of copper, suggesting mitigated ecological pressure.