Effects of exogenous bile acids (BAs) on growth, lipid profile, digestive enzymes, and immune responses of thinlip mullet, Liza ramada.

An eight-week trial was designed to explore the dietary effects of commercially purchased exogenous bile acids (BAs) on growth, whole-body composition, lipid profile, intestinal digestive enzymes, liver function enzymes, oxidative stress biomarkers, and serum immunity of thinlip mullet, Liza ramada. Four triplicate groups (10.50 ± 0.05 g) were fed four soybean meal (SBM)-based diets supplied with several BAs levels at 0 (control), 50, 130, or 350 mg/kg feed. Results indicated that the growth was significantly increased in groups fed BAs-based diets, especially at 130 mg/kg feed. The body composition analysis showed that feeding fish on diets supplied with BAs up to 130 mg/kg decreased moisture (%) alongside increased crude protein (%). However, the body composition of fish fed a diet with 350 mg BAs/kg had the lowest moisture (%) and the highest crude protein (%). Moreover, there were significant increases in the intestinal (protease, α-amylase, and lipase) enzyme activities in the groups supplied with BAs up to 130 mg BAs/kg. Liver function enzymes (aspartate aminotransferase and alanine aminotransferase enzyme activities) were significantly decreased in BAs-supplemented groups compared to those fed the BAs-free group. On the other hand, the control group had higher total cholesterol, triglycerides, and low-density lipoprotein alongside the lower high-density lipoprotein than BAs-supplemented groups, especially at 350 mg BAs/kg feed. BAs significantly decreased hepatic malondialdehyde concentrations and increased the activity of hepatic catalase, superoxide dismutase, and total antioxidant capacity compared with those reared on the control diet. Serum lysozyme, respiratory burst, and alternative complement activities were significantly increased in BAs-supplied groups, particularly in the group supplied with 130 mg BAs/kg compared to those fed on the control diet. Accordingly, our findings recommend that including 130 mg BAs/kg in an SBM-based diet enhanced the growth, digestive enzyme activities, and liver functions, alleviated oxidative stress, boosted serum immunity, and lowered lipid metabolites in thinlip mullet. These findings will be beneficial for improving the quality of feed prepared for feeding mullets and an effective alternative strategy to support mullet farming.

Selenium in the liver facilitates the biodilution of mercury in the muscle of Planiliza haematocheilus in the Jiaozhou Bay, China.

There are increasing evidences that the biodilution effect can significantly reduce the biomagnification of mercury (Hg) in fish. The significant antagonism of selenium (Se) -Hg may have a potential diluting effect on Hg in fish; however, there is still lack of knowledge on such effect. To reveal the Se-Hg interaction and its role in controlling the biodilution effect of Hg, we investigated levels of Hg and Se in the muscle and liver of redlip mullet from Jiaozhou Bay, China, an urbanized semi-enclosed bay highly impacted by human activities. In general, Hg levels in fish muscle were significantly negatively correlated to the levels of Se in the liver and fish size for fish with a size of < 200 mm, indicating that the antagonistic effect of Se on Hg increased with fish growth. This relationship was not significant for fish with a size of > 200 mm, possibly because the normal metabolism of Hg in muscle was hindered by homeostatic regulation or physiological activities such as gonadal development in vivo. Furthermore, the molar ratio of Se in the liver/Hg in the muscle was significantly increasing with Se/Hg in the liver, suggesting that the liver may be the key organ involved in Se-Hg antagonism. Moreover, both ratios continued to decrease with increasing fish size, implying that the antagonistic effect weakens with fish growth. These results indicate that Hg sequestration by liver may be a key mechanism of Se-Hg antagonism in fish and function as a driver for the biodilution effect of Hg, especially at a size of < 200 mm. These findings are further supported by the established linear model of Se-Hg antagonism at different developmental stages.

A Study on How Methionine Restriction Decreases the Body's Hepatic and Lipid Deposition in Rice Field Eel (Monopterus albus).

Methionine restriction reduces animal lipid deposition. However, the molecular mechanism underlying how the body reacts to the condition and regulates lipid metabolism remains unknown. In this study, a feeding trial was performed on rice field eel Monopterus albus with six isonitrogenous and isoenergetic feeds that included different levels of methionine (0, 2, 4, 6, 8, and 10 g/kg). Compared with M0 (0 g/kg), the crude lipid and crude protein of M. albus increased markedly in M8 (8 g/kg) (p < 0.05), serum (total cholesterol, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and non-esterified free fatty acids), and hepatic contents (hepatic lipase, apolipoprotein-A, fatty acid synthetase, total cholesterol, triglyceride, and lipoprteinlipase). However, in the serum, very-low-density lipoprotein and hepatic contents (hormone-sensitive triglyceride lipase, Acetyl CoA carboxylase, carnitine palmitoyltransterase, and mirosomal triglygeride transfer protein) decreased markedly in M8 (p < 0.05). The contents of hepatic C18:2n-6, C22:6n-3, and n-3PUFA in the M8 group were significantly higher than those in M0 (p < 0.05), and the contents of lipid droplets in M8 were higher than those in M0. Compared with M0, the hepatic gcn2, eif2α, hsl, mttp, ldlrap, pparα, cpt1, and cpt2 were remarkably downregulated in M8, while srebf2, lpl, moat2, dgat2, hdlbp, srebf1, fas, fads2, me1, pfae, and icdh were markedly upregulated in M8. Moreover, hepatic SREBP1 and FAS protein expression were upregulated significantly in M8 (p < 0.01). In short, methionine restriction decreased the lipid deposition of M. albus, especially for hepatic lipid deposition, and mainly downregulated hepatic fatty acid metabolism. Besides, gcn2 could be activated under methionine restriction.

Metabolite profiling, histological and oxidative stress responses in the grey mullet, Mugil cephalus exposed to the environmentally relevant concentrations of the heavy metal, Pb (NO3)2.

In this study, a metabolomics approach was applied to investigate the metabolic responses of grey mullet, Mugil cephalus to toxicity induced by heavy metal, Pb (NO3)2. In addition, the study was followed by assessing the peroxidation index and histology of liver as supplementary data. Pb (NO3)2 exposure affected the plasma metabolome, especially four group metabolites including amino acids, methylated metabolites, energetic metabolites and citric acid intermediates. Pb (NO3)2 in medium and high concentrations (15 and 25 µg/l) increased the levels of plasma amino acids compared to control (P < 0.01). In contrast, Pb (NO3)2 decreased the plasma levels of methylated metabolites (P < 0.01). The ketogenic metabolites and glycerol levels significantly elevated in fish exposed to 25 µg/l Pb (NO3)2 (P < 0.01). The plasma glucose levels increased in treatment, 5 µg/l Pb (NO3)2 and after a decline in treatment 15 µg/l Pb (NO3)2 elevated again in treatment 25 µg/l Pb (NO3)2 (P < 0.01).The plasma levels of lactate significantly increased in fish exposed to 5 and 15 µg/l Pb (NO3)2 and then declined to initial levels in treatment, 25 µg/l Pb (NO3)2 (P < 0.01). The plasma levels of TCA cycle intermediates significantly elevated in treatments 15 and 25 µg/l Pb (NO3)2 (P < 0.01). As a biomarker of oxidative stress, the plasma levels of malondialdehyde (MDA) showed significant increases in Pb (NO3)2 exposed fish (P < 0.01). During exposure period, wide ranges of liver tissue damages were also observed in Pb (NO3)2 exposed fish. In conclusion, exposure to Pb (NO3)2 affected the metabolome content of blood in grey mullet, mainly through inducing the biochemical pathways related to the metabolism of the amino acids, energetic metabolites and methylated metabolites. Our results may help to understand the effects of heavy metals on fish hematology from a molecular point of view.

Using ovarian and brain cell culture from the Mullet, Liza klunzingeri, to assess the inhibitory effects of benzo[a]pyrene on aromatase activity.

We assessed the toxic effects of benzo[a]pyrene (BaP) on cell viability, aromatase (Aro) activity and steroid production using ovarian and brain cell cultures obtained from Mullet, Liza klunzingeri. The brain and ovary were minced and digested, and the cells were suspended in Leibovitz's L-15 medium supplemented with 15% and 20% fetal bovine serum. The cell suspensions were seeded on 25-cm2 cell-culture flasks at 1 × 106 cells/mL and incubated at 25 °C for 2 weeks. A BaP concentration of 10-5 mol/L was accepted as the half-maximal inhibitory concentration. Ovarian and brain cells were exposed to different concentrations of BaP [0 (control), 10-6 , 2 × 10-6 , 3 × 10-6 mol/L] and incubated at 30 °C. At different sampling times (0, 12, 24 and 48 h) 40 ng/105 cells of 1,4,6-androstatriene-3,17-dione (ATD) was added to each well. Aro activity, 17ß-estradiol (E2) and ATD production were determined. The sensitivity of the cultivated ovarian and brain cells to BaP increased dose dependently. BaP was a potent inhibitor of Aro activity at 2 × 10-6 and 3 × 10-6 mol/L, both in the cultivated brain and ovarian cells at different sampling times, with 10-6 mol/L BaP found to be the least potent Aro inhibitor. E2 production decreased from cultivated ovarian and brain cells treated by different concentrations of BaP. In conclusion, BaP is able to change the activity of Aro and disrupt the biosynthesis of estrogens, and thus affects reproduction in fish.

Effects of water-accommodated fraction of diesel fuel on seahorse (Hippocampus reidi) biomarkers.

The present work aimed to investigate the effects of acute (12, 24, 48 and 96 h) and subchronic (168 and 336 h) exposure of seahorse, Hippocampus reidi to water-accommodated fraction (WAF) of diesel fuel on biotransformation parameters, antioxidant defenses and DNA integrity. In addition, a recovery experiment was performed, where the organisms remained in absence of the contaminant for 336 h, after WAF exposure for 168 h (totaling 504 h). At the end of each experimental protocol, the concentration of pyrene-, benzo(a)pyrene- and naphthalene-type metabolites in bile, hepatic activity of glutathione-S-transferase (GST), superoxide dismutase (SOD), and catalase (CAT), as well as lipid peroxidation (LPO) levels in hepatocytes, were analyzed, in addition to the DNA damage and the micronucleus (MN) test in the peripheral blood. It was observed that both acute and subchronic WAF exposure affected the investigated parameters in different ways. In general, the exposed groups presented higher mean values for the investigated parameters if compared with their respective controls. After the recovery experiment, the mean values of PAH metabolites, LPO, DNA damage and MN frequency were significantly lower than those of animals exposed for 168 h, indicating that the recovery period was appropriately long for the evaluated biomarkers return to the control levels. The results indicated that the selected H. reidi biomarkers proved to be adequate and complementary tools in determining the first impacts of acute and subchronic exposure caused by WAF of diesel fuel in fish, as well as their recovery in clean water.

Free radical scavenging activity of the peptide from the Alcalase hydrolysate of the edible aquacultural seahorse (Hippocampus abdominalis).

Seahorses, Hippocampus abdominalis, have a long history in traditional Chinese medicine as an important healthy ingredient in foods. This study evaluated the antioxidant activity of an enzymatic hydrolysate prepared from a seahorse bred in Jeju, South Korea. Experiments were performed in vitro using electron spin resonance spectrometry (ESR) to determine the free radical scavenging activity and in vivo using a zebrafish model to determine the protective effects against 2,2-azobis hydrochloride (AAPH)-induced oxidative damage. H. abdominalis protein hydrolysate (HPH) exhibited peroxyl radical scavenging activity (IC50  = 0.58 mg/ml) generated by the water-soluble AAPH (azo initiator of peroxyl radicals). HPH reduced dose-dependently both intracellular reactive oxygen species (ROS) levels in AAPH-induced cells and cell death in AAPH-induced zebrafish embryos. The antioxidant peptide purified from HPH was identified as a tripeptide (alanine-glycine-aspartic acid) using Q-TOF ESI mass spectroscopy. Thus, this study demonstrated that HPH contains antioxidant peptides that exhibit a strong antioxidant activity. PRACTICAL APPLICATIONS: Hippocampus abdominalis is one of the largest seahorse species and cultivated in many countries. Because of its large body size compared to other seahorse species, H. abdominalis has acquired considerable consumer attraction in the global market. Owing to its biologically useful properties, it recently gained attention as the natural products obtained from H. abdominalis have varied applications in the field of medicine, health care products, and functional foods. Thus, commercial products of this particular seahorse species are popular among customers, especially in China. The purpose of this study was to evaluate the antioxidant property of H. abdominalism, cultured in a commercial seahorse farm in Jeju Island. Owing to its prominent antioxidant activity, it could be used as an ingredient in medicinal preparations, nutraceuticals, and functional foods.

Copper-zinc-superoxide dismutase (CuZnSOD), an antioxidant gene from seahorse (Hippocampus abdominalis); molecular cloning, sequence characterization, antioxidant activity and potential peroxidation function of its recombinant protein.

Copper-zinc-superoxide dismutase (CuZnSOD) from Hippocampus abdominalis (HaCuZnSOD) is a metalloenzyme which belongs to the ubiquitous family of SODs. Here, we determined the characteristic structural features of HaCuZnSOD, analyzed its evolutionary relationships, and identified its potential immune responses and biological functions in relation to antioxidant defense mechanisms in the seahorse. The gene had a 5' untranslated region (UTR) of 67 bp, a coding sequence of 465 bp and a 3' UTR of 313 bp. The putative peptide consists of 154 amino acids. HaCuZnSOD had a predicted molecular mass of 15.94 kDa and a theoretical pI value of 5.73, which is favorable for copper binding activity. In silico analysis revealed that HaCuZnSOD had a prominent Cu-Zn_superoxide_dismutase domain, two Cu/Zn signature sequences, a putative N-glycosylation site, and several active sites including Cu(2+) and Zn(2+) binding sites. The three dimensional structure indicated a ß-sheet barrel with 8 ß-sheets and two short α-helical regions. Multiple alignment analyses revealed many conserved regions and active sites among its orthologs. The highest amino acid identity to HaCuZnSOD was found in Siniperca chuatsi (87.4%), while Maylandia zebra shared a close relationship in the phylogenetic analysis. Functional assays were performed to assess the antioxidant, biophysical and biochemical properties of overexpressed recombinant (r) HaCuZnSOD. A xanthine/XOD assay gave optimum results at pH 9 and 25 °C indicating these may be the best conditions for its antioxidant action in the seahorse. An MTT assay and flow cytometry confirmed that rHaCuZnSOD showed peroxidase activity in the presence of HCO3(-). In all the functional assays, the level of antioxidant activity of rHaCuZnSOD was concentration dependent; metal ion supplementation also increased its activity. The highest mRNA expressional level of HaCuZnSOD was found in blood. Temporal assessment under pathological stress showed a delay response by HaCuZnSOD. Our findings demonstrated that HaCuZnSOD is an important antioxidant, which might be involved in the host antioxidant defense mechanism against oxidative stress.

Natural Product Screening Reveals Naphthoquinone Complex I Bypass Factors.

Deficiency of mitochondrial complex I is encountered in both rare and common diseases, but we have limited therapeutic options to treat this lesion to the oxidative phosphorylation system (OXPHOS). Idebenone and menadione are redox-active molecules capable of rescuing OXPHOS activity by engaging complex I-independent pathways of entry, often referred to as "complex I bypass." In the present study, we created a cellular model of complex I deficiency by using CRISPR genome editing to knock out Ndufa9 in mouse myoblasts, and utilized this cell line to develop a high-throughput screening platform for novel complex I bypass factors. We screened a library of ~40,000 natural product extracts and performed bioassay-guided fractionation on a subset of the top scoring hits. We isolated four plant-derived 1,4-naphthoquinone complex I bypass factors with structural similarity to menadione: chimaphilin and 3-chloro-chimaphilin from Chimaphila umbellata and dehydro-α-lapachone and dehydroiso-α-lapachone from Stereospermum euphoroides. We also tested a small number of structurally related naphthoquinones from commercial sources and identified two additional compounds with complex I bypass activity: 2-methoxy-1,4-naphthoquinone and 2-methoxy-3-methyl-1,4,-naphthoquinone. The six novel complex I bypass factors reported here expand this class of molecules and will be useful as tool compounds for investigating complex I disease biology.

Bioaccumulation of Metals in Tissues of Seahorses Collected from Coastal China.

Seahorses, which have been used in Chinese traditional medicine, are poor swimmers and easily affected by regional ecological conditions. In this study, we investigated the bioaccumulation of nine metals in different tissues of four seahorse species (Hippocampus trimaculatus, H. histrix, H. kelloggi, and H. kuda) from six locations along the Chinese coast. The present study found relatively low concentrations of metals in the seahorses compared with those in other marine fishes. There was a location-dependent variation in metal concentrations in the seahorses, especially between developed and less developed cities. Results also showed metal concentrations varied among different seahorse species and tissues, with H. kelloggi having higher bioaccumulation ability compared with H. trimaculatus and higher metal levels were found in visceral mass, muscle, and skin tissues than those in brain, lips gill, endoskeleton, and exoskeleton tissues in the seahorses. Among different metals, Mg had the highest tissue concentrations in all the seahorses, followed by Al and Mn.

GnRH mRNA levels in male three-spined sticklebacks, Gasterosteus aculeatus, under different reproductive conditions.

In vertebrates, reproduction is regulated by the brain-pituitary-gonad (BPG) axis, where the gonadotropin-releasing hormone (GnRH) is one of the key components. However, very little is known about the possible role of GnRH in the environmental and feedback control of fish reproduction. To investigate this, full-length gnrh2 (chicken GnRH II) and gnrh3 (salmon GnRH) sequences of male three-spined sticklebacks (Gasterosteus aculeatus), which are clustered with the taxa of the same GnRH type as other Euteleostei, were cloned and annotated. gnrh1 is absent in this species. The mRNA levels of gnrh2 and gnrh3 in the sticklebacks' brain were measured under breeding and post-breeding conditions as well as in castrated and sham-operated breeding fish and castrated/sham-operated fish kept under long-day (LD 16:8) and short-day (LD 8:16) conditions. Fully breeding males had considerably higher mRNA levels of gnrh2 and gnrh3 in the thalamus (Th) and in the telencephalon and preoptic area (T+POA), respectively, than post-breeding males. Sham-operated breeding males have higher gnrh3 mRNA levels than the corresponding castrated males. Moreover, higher gnrh2 mRNA levels in the Th and higher gnrh3 mRNA levels in the T+POA and hypothalamus (HypTh) were also found in long-day sham-operated males than in sham-operated fish kept under an inhibitory short day photoperiod. Nevertheless, gnrh2 and gnrh3 mRNA levels were not up-regulated in castrated males kept under long-day photoperiod, which suggests that positive feedbacks on the brain-pituitary-gonad axis are necessary for this response.

Properties and expression of Na+/K+-ATPase α-subunit isoforms in the brain of the swamp eel, Monopterus albus, which has unusually high brain ammonia tolerance.

The swamp eel, Monopterus albus, can survive in high concentrations of ammonia (>75 mmol l(-1)) and accumulate ammonia to high concentrations in its brain (4.5 µmol g(-1)). Na(+)/K(+)-ATPase (Nka) is an essential transporter in brain cells, and since NH4(+) can substitute for K(+) to activate Nka, we hypothesized that the brain of M. albus expressed multiple forms of Nka α-subunits, some of which might have high K(+) specificity. Thus, this study aimed to clone and sequence the nka α-subunits from the brain of M. albus, and to determine the effects of ammonia exposure on their mRNA expression and overall protein abundance. The effectiveness of NH4(+) to activate brain Nka from M. albus and Mus musculus was also examined by comparing their Na(+)/K(+)-ATPase and Na(+)/NH4(+)-ATPase activities over a range of K(+)/NH4(+) concentrations. The full length cDNA coding sequences of three nkaα (nkaα1, nkaα3a and nkaα3b) were identified in the brain of M. albus, but nkaα2 expression was undetectable. Exposure to 50 mmol l(-1) NH4Cl for 1 day or 6 days resulted in significant decreases in the mRNA expression of nkaα1, nkaα3a and nkaα3b. The overall Nka protein abundance also decreased significantly after 6 days of ammonia exposure. For M. albus, brain Na(+)/NH4(+)-ATPase activities were significantly lower than the Na(+)/K(+)-ATPase activities assayed at various NH4(+)/K(+) concentrations. Furthermore, the effectiveness of NH4(+) to activate Nka from the brain of M. albus was significantly lower than that from the brain of M. musculus, which is ammonia-sensitive. Hence, the (1) lack of nkaα2 expression, (2) high K(+) specificity of K(+) binding sites of Nkaα1, Nkaα3a and Nkaα3b, and (3) down-regulation of mRNA expression of all three nkaα isoforms and the overall Nka protein abundance in response to ammonia exposure might be some of the contributing factors to the high brain ammonia tolerance in M. albus.

Effect of dispersed crude oil exposure upon the aerobic metabolic scope in juvenile golden grey mullet (Liza aurata).

This study evaluated the toxicity of dispersant application which is, in nearshore area, a controversial response technique to oil spill. Through an experimental approach with juveniles of Liza aurata, the toxicity of five exposure conditions was evaluated: (i) a chemically dispersed oil simulating dispersant application; (ii) a single dispersant as an internal control of chemically dispersed oil; (iii) a mechanically dispersed oil simulating natural dispersion of oil; (iv) a water soluble fraction of oil simulating an undispersed and untreated oil slick and (v) uncontaminated seawater as a control exposure condition. The relative concentration of PAHs (polycyclic aromatic hydrocarbons) biliary metabolites showed that the incorporation of these toxic compounds was increased if the oil was dispersed, whether mechanically or chemically. However, toxicity was not observed at the organism level since the aerobic metabolic scope and the critical swimming speed of exposed fish were not impaired.

Seahorses - a source of traditional medicine.

Wild marine organisms have been used in the discovery and development of traditional and allopathic medical treatments for a long time. Seahorses, a syngnathidae fish, are one of the important candidate organisms which have been used in Chinese traditional medicine from time immemorial. It is believed that seahorses have the potential to cure infertility, baldness, asthma and arthritis. An authentic research work on the biomedical validation of seahorses proved that they have the ability to cure arthritis and its associated inflammation. A Cathepsin-derived peptide from the seahorse species of Hippocampus kuda proved to be effective in chondrocyte cells and its associated impaired arthritis inflammation. Apart from this, seahorses have a putative free radical scavenging effect in controlling the ageing process. More authentic research is needed in order to validate the biomedical potential. This article highlights the role of seahorses' value in traditional medicine and their biomedical properties.

Bioassay-guided isolation of a novel protein with antitumor activity from Trachyrhamphus serratus (Syngnathidae).

A novel protein with antitumor activity, Hailongin, was purified from the aqueous extract of the whole body of Trachyrhamphus serratus, which is commonly used in traditional Chinese medicine, by bioassay-guided fractionation. Hailongin exhibited strong inhibition of proliferation of the tested human cell lines, such as A549, HeLa, LoVo and CCRF-CEM. The IC(50) values of Hailongin ranged from 5.4 to 25.7 µ/mL. An in vivo study showed that the growth of implanted S-180 solid tumors in mice was significantly inhibited by Hailongin treatment, while the immunological function of the tumor-bearing mice was enhanced. The molecular weight and the isoelectric point of Hailongin were 57.074 kDa (by MALDI-TOF-MS) and 6.2 (by isoelectric focusing-polyacrylamide gel electrophoresis), respectively. Seventeen amino acids were identified in Hailongin. The acidic amino acids accounted for the majority of Hailongin's amino acid composition. The N-terminal amino acid sequence of Hailongin was determined to be IVPYSHNAGNKGLTQMR and showed no significant homology with known proteins.

Comparative toxicity of eight oil dispersants, Louisiana sweet crude oil (LSC), and chemically dispersed LSC to two aquatic test species.

The present study describes the acute toxicity of eight commercial oil dispersants, South Louisiana sweet crude oil (LSC), and chemically dispersed LSC. The approach used consistent test methodologies within a single laboratory in assessing the relative acute toxicity of the eight dispersants, including Corexit 9500A, the predominant dispersant applied during the DeepWater Horizon spill in the Gulf of Mexico. Static acute toxicity tests were performed using two Gulf of Mexico estuarine test species, the mysid shrimp (Americamysis bahia) and the inland silversides (Menidia beryllina). Dispersant-only test solutions were prepared with high-energy mixing, whereas water-accommodated fractions of LSC and chemically dispersed LSC were prepared with moderate energy followed by settling and testing of the aqueous phase. The median lethal concentration (LC50) values for the dispersant-only tests were calculated using nominal concentrations, whereas tests conducted with LSC alone and dispersed LSC were based on measured total petroleum hydrocarbon (TPH) concentrations. For all eight dispersants in both test species, the dispersants alone were less toxic (LC50s: 2.9 to >5,600 µl/L) than the dispersant-LSC mixtures (0.4-13 mg TPH/L). Louisiana sweet crude oil alone had generally similar toxicity to A. bahia (LC50: 2.7 mg TPH/L) and M. beryllina (LC50: 3.5 mg TPH/L) as the dispersant-LSC mixtures. The results of the present study indicate that Corexit 9500A had generally similar toxicity to other available dispersants when tested alone but was generally less toxic as a mixture with LSC.

Toxicity of dispersant application: Biomarkers responses in gills of juvenile golden grey mullet (Liza aurata).

Dispersant use in nearshore areas is likely to increase the exposure of aquatic organisms to petroleum. To measure the toxicity of this controversial response technique, golden grey mullets (Liza aurata) were exposed to mechanically dispersed oil, chemically dispersed oil, dispersant alone in seawater, water-soluble fraction of oil and to seawater as a control treatment. Several biomarkers were assessed in the gills (enzymatic antioxidant activities, glutathione content, lipid peroxidation) and in the gallbladder (polycylic aromatic hydrocarbons metabolites). The significant differences between chemically dispersed oil and water soluble fraction of oil highlight the environmental risk to disperse an oil slick when containment and recovery can be conducted. The lack of significance between chemically and mechanically dispersed oil suggests that dispersant application is no more toxic than the natural dispersion of the oil slick. The results of this study are of interest in order to establish dispersant use policies in nearshore areas.

Effects of dispersed oil exposure on the bioaccumulation of polycyclic aromatic hydrocarbons and the mortality of juvenile Liza ramada.

Dispersing an oil slick is considered to be an effective response to offshore oil spills. However, in nearshore areas, dispersant application is a controversial countermeasure: environmental benefits are counteracted by the toxicity of dispersant use. In our study, the actual toxicity of the dispersant response technique in the nearshore areas was evaluated through an experimental approach using juvenile Liza ramada. Fish were contaminated via the water column (i) by chemically dispersed oil, simulating dispersant application, (ii) by dispersant, as an internal control of chemical dispersion, (iii) by mechanically dispersed oil, simulating only the effect of natural mixing processes, without dispersant application, and (iv) by the water soluble fraction of oil, simulating the toxicity of an oil slick before recovery. Bioconcentrations of polycyclic aromatic hydrocarbons (PAH) and mortality were evaluated, and related to both total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) concentrations in seawater. Fish exposed to chemically dispersed oil showed both a higher bioconcentration of PAH and a higher mortality than fish exposed to either the water soluble fraction of oil or the mechanically dispersed oil. These results suggest that (i) dispersion is a more toxic response technique than containment and recovery of the oil slick; (ii) in turbulent mixing areas, dispersant application increases the environmental risk for aquatic organisms living in the water column. Even if the experimental aspects of this study compel us to be cautious with our conclusions, responders could consider these results to establish a framework for dispersant use in nearshore areas.

Osmoregulation of the resident estuarine fish Atherinella brasiliensis was still affected by an oil spill (Vicuña tanker, Paranaguá Bay, Brazil), 7 months after the accident.

An oil tanker loaded with methanol and bunker oil has exploded in November 2004 in Paranaguá Bay, in front of Paranaguá Harbor, southern Brazil. In order to investigate the chronic effects of an oil spill on a resident estuarine fish, the Brazilian silverside Atherinella brasiliensis was sampled 1, 4, and 7 months after the spill, from 2 sites inside Paranaguá Bay, and also from a reference site inside nearby Guaratuba Bay, non-affected by the spill. Increases in plasma osmolality (reaching ~525 mOsm/kg H2O, or ~70% above values in reference fish) and chloride (reaching 214 mM in site C, or ~51% above values in reference fish) were detected 4 months after the spill, in parallel with branchial carbonic anhydrase inhibition (to 56% of the activity measured in reference fish) in silversides obtained from the contaminated sites. Plasma cortisol concentration increased progressively in samples from fish obtained 4 (462 ng/mL) and 7 (564-650 ng/mL) months after the spill, when compared to values in reference fish (192 ng/mL). Osmoregulation of a resident estuarine fish is still affected by an oil spill, months after the accident. It is, thus, a sensitive tool for the evaluation of the chronic effects of oil spills inside tropical estuarine systems, and A. brasiliensis is proposed as an adequate sentinel species for monitoring protocols.

Liver antioxidant and plasma immune responses in juvenile golden grey mullet (Liza aurata) exposed to dispersed crude oil.

Dispersants are often used after oil spills. To evaluate the environmental cost of this operation in nearshore habitats, the experimental approach conducted in this study exposed juvenile golden grey mullets (Liza aurata) for 48 h to chemically dispersed oil (simulating, in vivo, dispersant application), to dispersant alone in seawater (as an internal control of chemically dispersed oil), to mechanically dispersed oil (simulating, in vivo, natural dispersion), to the water-soluble fraction of oil (simulating, in vivo, an oil slick confinement response technique) and to seawater alone (control condition). Biomarkers such as fluorescence of biliary polycyclic aromatic hydrocarbon (PAH) metabolites, total glutathione liver content, EROD (7-ethoxy-resorufin-O-deethylase) activity, liver antioxidant enzyme activities, liver lipid peroxidation and an innate immune parameter (haemolytic activity of the alternative complement pathway) were measured to assess the toxicity of dispersant application. Significant responses of PAH metabolites and total glutathione content of liver to chemically dispersed oil were found, when compared to water-soluble fraction of oil. As was suggested in other studies, these results highlight that priority must be given to oil slick confinement instead of dispersant application. However, since the same patterns of biomarker responses were observed for both chemically and mechanically dispersed oil, the results also suggest that dispersant application is no more toxic than the natural dispersion occurring in nearshore areas (due to, e.g. waves). The results of this study must, nevertheless, be interpreted cautiously since other components of nearshore habitats must be considered to establish a framework for dispersant use in nearshore areas.