The impact of various carbon nanomaterials on the morphological, behavioural, and biochemical parameters of rainbow trout in the early life stages.

With the increasing production and the number of potential applications of carbon nanomaterials, mainly from the graphene family, their release into the natural environment, especially to aquatic ecosystems, is inevitable. The aim of the study was to determine the effects of various carbon nanomaterials (graphene nanoflakes (GNF), graphene oxide (GO), reduced graphene oxide (RGO) and silicon carbide nanofibers (NFSiC) in the concentration of 4 mg L-1 on the early life stages of the rainbow trout Oncorhynchus mykiss. The survival rates of O. mykiss were not affected after 36 days of exposure to studied materials, except for RGO, which caused significant mortality of both embryos and larvae compared to the control conditions. Larvae exposed to GO and NFSiC were characterized by a smaller standard body length at hatch, whereas at the end of the experiment, the growth of fish exposed to all materials was accelerated, especially in GO and RGO treatment, in which higher body weight and length were accompanied by lower volume of the yolk sac. Neither the markers of the oxidative damage nor the antioxidant enzymes activities were significantly affected in embryos, newly hatched larvae and larvae after 26-day exposure to studied carbon nanomaterials. Also, no neurotoxic effect expressed by the activity of the whole-body acetylcholinesterase was observed. Nevertheless, the significant increase in the velocity and the overall activity of larvae exposed to GNF (not investigated after exposure to other materials) must be highlighted. The most pronounced effect of RGO might be connected with its large particle size, sharp edges, and the presence of TiO2 nanoparticles. The results indicate for the first time that various carbon nanomaterials potentially released into aquatic ecosystems may have serious developmental implications for the early life stages of salmonid fish.

Microplastics cause neurotoxicity and decline of enzymatic activities in important bioturbator Hediste diversicolor.

Microplastics (MPs) tend to accumulate in marine sediments thus benthic fauna is particularly vulnerable to microplastic pollution. Hediste diversicolor is a widespread species in coastal marine sediments. It plays key ecological functions mostly related to bioturbation process which means sediment reworking due to the worm burrowing activity and building a network of galleries. Herein, we show that commercial plastic microspheres of two sizes (63-75 and 300-355 µm) have the potential to cause neurotoxicity in H. diversicolor. The whole-body acetylcholinesterase (AChE) activity - a common indicator of neurotoxic effect - was on average 60% lower in polychaetes exposed for 28 days to MPs served at environmentally relevant concentrations (0.08% sediment d. wt.), than in unexposed ones. Significantly reduced activities of antioxidant enzymes (SOD, CAT, GST) indicated suppression of the cellular antioxidative system in worms exposed to MPs. No changes were, however, observed in tGSH, lipid or protein oxidation measures (CBO, MDA), and in the energetic value of these polychaetes. The response was generally similar with no regard to MPs size. Only very few microspheres were found in polychaetes exposed to MPs spiked sediment. The potential role of MPs-associated pollutants as a factor responsible for observed biochemical effects, is discussed.

Do magnetic fields related to submarine power cables affect the functioning of a common bivalve?

The aim of the study was to determine the effect of static magnetic field (SMF) and electromagnetic field (EMF), of values usually recorded near submarine cables, on the bioenergetics, oxidative stress, and neurotoxicity in the cockle Cerastoderma glaucum. Bivalves maintained a positive energy balance, but the filtration rate and energy available for individual production were significantly lower in SMF-exposed animals compared to the control treatment. No changes in the respiration were noted but ammonia excretion rate was significantly lower after exposure to EMF. Changes in the activities of antioxidant enzymes and the lipid peroxidation were not observed however, exposure to both fields resulted in increased protein carbonylation. After exposure to EMF a significant inhibition of acetylcholinesterase activity was observed. As the present study for the first time revealed the oxidative damage and neurotoxicity in marine invertebrate after exposure to artificial magnetic fields, the need for further research is highlighted.

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.

Effects of different types of primary microplastics on early life stages of rainbow trout (Oncorhynchus mykiss).

Plastic pollution is recognized as serious threat to aquatic organisms. The aim of this research was to determine the effect of environmentally realistic concentrations of various microplastics (MPs) on survival, growth, development and induction of endocrine, geno- and cytotoxic responses in the early life stages of rainbow trout Oncorhynchus mykiss. Fish were exposed for 69-days, from embryos at eyed-stage to mobile yolk-sac larvae, to pre-production pellets (3000 µm; polystyrene - PS and polyethylene terephthalate - PET). Additionally, since salmonid larvae are particularly exposed to light polymers after swimming up from the bottom, fish were also treated with PE microspheres (150-180 µm; polyethylene - PE) for both long (69-days, from embryos at eyed-stage) and short period (29 days, from larvae 3 weeks after hatching) to test the development stage-related effect on the growth parameters and fitness. Hatching success, rate and the survival of larvae did not differ among treatments. Although some alterations were found in the length gain after the long-term exposure and in the yolk-sac exhaustion rate in all PE treatments, the final size of larvae did not differ from the respective controls. PE-treated larvae have shown elevated corticosterone concentrations being significantly higher in fish exposed from the embryo stage. It was indicated for the first time that mobile yolk-sac larvae ingested MPs (up to 24% of larvae contained microspheres). No changes were recorded in cytotoxicity endpoints in any of the treatments, but exposure to PS pellets resulted in significantly higher frequencies of genotoxicity endpoints compared to the control treatment. This effect and aforementioned alterations in PE-treated larvae might result from the exposure to toxic MPs leaches. The fact that selected PAHs' levels reached the highest values in PS pellets and PE microspheres must be underlined.

Response of sediment-dwelling bivalves to microplastics and its potential implications for benthic processes.

Sediments are considered an ultimate sink for microplastic (MPs) but knowledge on MPs impacts on the benthic organisms is still limited. A microcosm experiment was performed to assess the effect of MPs on two sediment-dwelling bivalve species that differ in terms of their life¬styles and feeding behaviors (the cockle Cerastoderma glaucum and the Baltic clam Limecola balthica). Fitness of both bivalves, their vertical distribution in the sediment and activity at the sediment-water interface were studied following addition of PE microspheres of three different size fractions (63-75, 150-180 and 250-300 µm) in two concentrations (0.1 and 0.5% sediment dwt) to the sediment surface. Bivalve survival was generally high and did not vary significantly among treatments. Both bivalve species captured MPs but no significant effect on their body conditions and energy reserves was observed. However, some behavioural alterations were found. The near-surface-dwelling C. glaucum emerged from the sediment less often and in lower numbers suggesting lower activity in sediments amended with large and medium MPs served in higher concentration. Also vertical distribution of deeper-dwelling L. balthica differed among treatments. The clam penetrated deeper sediment layers in microcosms treated with MPs than in the control (on average 62% of the total number of bivalves found in the sediment layer 2-4 cm vs. 65% in the upper 2 cm) which may suggest an avoidance behaviour or escape reaction in response to MPs addition to the topmost sediment. Total sediment community oxygen consumption was significantly higher in MPs-amended sediments than in the control, with the highest rates in treatment with the largest microspheres. However, oxygen uptake increase seemed to be unrelated to addition of MPs per se, suggesting rather an interaction between MPs and bivalves. The need for future studies on MPs effects on benthic community structure and functioning is highlighted.

Effects of chronic exposure to microplastics of different polymer types on early life stages of sea trout Salmo trutta.

The aim of the present study was to determine the effect of a long-term (113 days) exposure to microplastics on the development and induction of endocrine, geno- and cytotoxic responses in early life stages of sea trout Salmo trutta. Microplastic particles (3000 µm) of three most commonly mass-produced polymers (polystyrene - PS, polyethylene terephthalate - PET and polyethylene - PE) were applied in environmentally realistic concentrations (0.1% of sediment dry weight) in a laboratory experiment imitating the natural environment, typical for sea trout spawning grounds. The exposure of the sea trout, from fertilized eggs to mobile yolk-sac larvae, to microplastics did not affect the hatching success (the survival of embryos), hatching rate and the incubation period. Microplastics of any tested polymer type also had no adverse effect on the larvae survival, growth rate and the rate of yolk sack absorption. Similarly, no changes in frequencies of detected cytotoxicity endpoints compared to the control group were recorded. Exposure to polymer particles induced however the formation of genotoxicity endpoints (nuclear buds, micronuclei and blebbed nuclei cells). The level of total genotoxicity (ΣGentox) in fish larvae erythrocytes increased significantly in the following sequence: PS > PET > PE. No significant changes in the whole body corticosterone, dehydrocorticosterone and cortisone concentrations due to exposure to microplastics were recorded, while cortisol was detected in larvae exposed to PS. Our results show that long-term, non-ingestion related exposure to microplastics does not affect development of S. trutta early life stages but may lead to genotoxic responses. PS seems to be the most hazardous among all polymers studied. This is the first study demonstrating non-ingestion related toxicity of microplastics to the early life stages of fish.