Effects of the sea lice bath treatment pharmaceuticals hydrogen peroxide, azamethiphos and deltamethrin on egg-carrying shrimp (Pandalus borealis)

Without a pinch of salt: effect of low salinity on eggs and nauplii of the salmon louse (Lepeophtheirus salmonis)

The salmon louse is an economically important parasite on Atlantic salmon and poses a major threat to aquaculture. Several treatment methods have lost their effect due to resistance development in the lice. A rather new method for combatting sea lice is freshwater treatment where the various life stages of lice are differently affected by this treatment. In this study, we analyzed the effect of freshwater on the egg strings. A 3-h treatment with freshwater had a detrimental effect on the egg strings. First, the water penetrated the string, widening it, then entering the eggs and enlarging them. Finally, the ordered structure of the egg strings collapsed, and no alive animals hatched. Shorter treatments had a lower effectivity, and treatments with brackish water also showed milder effects. The egg strings were found to have a protective effect against low salinities, as hatched nauplii died rapidly under conditions that embryos survived. We also found that embryos react to low salinity on a molecular level by changing gene expression of several genes, when incubated in brackish water. Additionally, the hatching of embryos treated with brackish water was delayed in comparison to seawater controls.

Acute and Sublethal Effects of Deltamethrin Discharges from the Aquaculture Industry on Northern Shrimp (Pandalus borealis Krøyer, 1838): Dispersal Modeling and Field Investigations

Pharmaceutical deltamethrin (Alpha Max), used as delousing treatments in aquaculture, has raised concerns due to possible negative impacts on the marine environment. A novel approach combining different scientific disciplines has addressed this topic. Acute (mortality) and sublethal effects (i.e., fitness, neurological, immunological, and oxidative responses) of exposure of northern shrimp (Pandalus borealis) were studied in laboratory experiments. Passive water sampling combined with sediment analyses revealed environmental concentrations. Finally, dispersal modeling was performed to predict environmental concentrations. Ecotoxicological analyses showed mortality in shrimp after 1 h of exposure to 2 ng L^-1 (1000-fold dilution of treatment dose), revealing a high sensitivity to deltamethrin. Sublethal effects included induction of acetylcholinesterase and acyl CoA oxidase activities and oxidative impairment, which may be linked to neurotoxic responses. Field concentrations of 10-200 ng L^-1 in water (100 m from the pens) and <LOD-0.19 ng g^-1 dw in sediment (0-400 m from pens) were measured. Ecotoxicological values were compared with measured and modeled concentrations. They showed that concentrations higher than those causing mortality could be expected up to 4-5 km from point of release, in an area of 6.4 km², with lethal concentrations remaining up to 35 h in some areas. Hence, the study demonstrates that there is a considerable risk for negative effects on the ecologically and commercially important shrimp.

Interspecific differences in oxidative DNA damage after hydrogen peroxide exposure of sea urchin coelomocytes

Interspecific comparison of DNA damage can provide information on the relative vulnerability of marine organisms to toxicants that induce oxidative genotoxicity. Hydrogen peroxide (H2O2) is an oxidative toxicant that causes DNA strand breaks and nucleotide oxidation and is used in multiple industries including Atlantic salmon aquaculture to treat infestations of ectoparasitic sea lice. H2O2 (up to 100 mM) can be released into the water after sea lice treatment, with potential consequences of exposure in nontarget marine organisms. The objective of the current study was to measure and compare differences in levels of H2O2-induced oxidative DNA damage in coelomocytes from Scottish sea urchins Echinus esculentus, Paracentrotus lividus, and Psammechinus miliaris. Coelomocytes were exposed to H2O2 (0-50 mM) for 10 min, cell concentration and viability were quantified, and DNA damage was measured by the fast micromethod, an alkaline unwinding DNA method, and the modified fast micromethod with nucleotide-specific enzymes. Cell viability was >92% in all exposures and did not differ from controls. Psammechinus miliaris coelomocytes had the highest oxidative DNA damage with 0.07 ± 0.01, 0.08 ± 0.01, and 0.07 ± 0.01 strand scission factors (mean ± SD) after incubation with phosphate-buffered saline, formamidopyrimidine-DNA glycosylase, and endonuclease-III, respectively, at 50 mM H2O2. Exposures to 0.5 mM H2O2 (100-fold dilution from recommended lice treatment concentration) induced oxidative DNA damage in all three species of sea urchins, suggesting interspecific differences in vulnerabilities to DNA damage and/or DNA repair mechanisms. Understanding impacts of environmental genotoxicants requires understanding species-specific susceptibilities to DNA damage, which can impact long-term stability in sea urchin populations in proximity to aquaculture farms.

Determination of 15 human pharmaceutical residues in fish and shrimp tissues by high-performance liquid chromatography-tandem mass spectrometry

An efficient, reliable, and sensitive multiclass analytical method has been expanded to simultaneously determine 15 human pharmaceutical residues in fish and shrimp tissue samples by ultra-high-performance liquid chromatography-tandem mass spectrometry. The investigated compounds comprise ten classes, namely, analgesic, antibacterial, anticonvulsant, cardiovascular, fluoroquinolones, macrolides, nonsteroidal anti-inflammatory, penicillins, stimulant, and sulfonamide. A simple liquid extraction procedure based on 0.1% formic acid in methanol was developed. Chromatographic conditions were optimized, and mobile phase A was 0.1% ammonium acetate, and mobile phase B was acetonitrile. The mobile phase's gradient program was as follows: 0-2 min, 15% B; 2-5 min, linear to 95% B; 5-10 min, 95% B; and 10-12 min. The limits of detection were from 0.017 to 1.371 μg/kg, while a quantification range was measured from 0.051 to 4.113 μg/kg. Finally, amoxicillin, azithromycin, caffeine, carbamazepine, ciprofloxacin, clarithromycin, diclofenac, erythromycin, furosemide, ibuprofen, ketoprofen, naproxen, sulfamethoxazole, tetracycline, and triclosan were quantifiable in fish and shrimp samples.

Highly Sensitive Detection of the Insecticide Azamethiphos by Tris(2,2'-bipyridine)ruthenium(II) Electrogenerated Chemiluminescence

Azamethiphos (AZA) is an insecticide and neurotoxic agent that causes the inhibition of acetylcholinesterase (AChE). AChE is a vital enzyme for neurotransmission because it metabolizes acetylcholine neurotransmitter at the synaptic cleft and terminates synaptic transmission. It is worth mentioning that organophosphates and carbamates inhibit AChE. These AChE inhibitors bind to the active site of the enzyme and inactivate it, leading to paralysis and death. Herein, for the first time, we develop a sensitive, low-cost, and rapid electrogenerated chemiluminescence (ECL) system for the detection of AZA. The designed ECL sensor was applied for the highly sensitive detection of AZA with a wide dynamic range (from 0.1 μM to 1000 μM) and low detection limit of 0.07 μM (S/N = 3). The practical utility of the sensor demonstrates high recoveries (96-102%) in real samples of lake water and wastewater.

Chronic exposure of hydrogen peroxide alters redox state, apoptosis and endoplasmic reticulum stress in common carp (Cyprinus carpio)

Hydrogen peroxide (H₂O₂) appears to be ubiquitous in natural water. Higher level of H₂O₂ can cause physiological stress, immunosuppression and even death in aquatic animals, but the physiological and molecular mechanisms of H₂O₂ toxicity are not well studied. Thus, the aim of the present study was to exposure potential toxic mechanisms of H₂O₂ via assessing the effects on redox state, apoptosis and endoplasmic reticulum (ER) stress in common carp. The fish were subjected to four concentrations of H₂O₂ (0, 0.25, 0.5 and 1 mM) for 14 days. And then, the tissues including blood, liver, muscle, gills, intestines, heart, kidney and spleen were collected to measure biochemical parameter and gene expression. The results showed that H₂O₂ exposure suppressed the majority antioxidative parameters in serum, liver, muscle and intestines, but enhanced T-SOD, CAT and T-AOC levels in gills. In all tested tissues, the MDA content was significantly promoted by H₂O₂ exposure. The oxidative stress-related genes including nrf2, gstα, sod, cat and/or gpx1 were upregulated in liver, gills, muscle, intestines, and/or kidney, but downregulated in heart after H₂O₂ exposure. Moreover, the ho-1 mRNA level was inhibited by H₂O₂ exposure in all tissues except intestines and spleen. After 14 days of exposure, H₂O₂ induced ER stress and initiated IRE1 and PERK pathways, which activated downstream genes, including chop, grp78 and/or xbp1s, to regulate UPR in liver, gills, muscle and/or heart. Meanwhile, H₂O₂ exposure activated MAPK pathway to regulate mitochondria-related genes including bcl-2, bax and cytc, which further triggered cas-8, cas-9 and cas-3, and accelerated apoptosis in liver, gills, muscle and heart. Importantly, in different tissues, the genes associated with oxidative stress, ER stress and apoptosis showed a different influence, and more significant influence was observed in the muscle, gills and liver. Overall results suggested that long-term H₂O₂ exposure induced oxidative stress, ER stress and apoptosis in the majority of tested tissues of common carp. The Nrf2, IRE1, PERK and MAPK pathways played important roles in H₂O₂-induced toxicity in fish. These data enriched the toxicity mechanism of H₂O₂ in fish, which might contribute to the risk assessment of H₂O₂ in aquatic environment.