Salmonid smolt caudal fin and liver transcriptome responses to low sulfur marine diesel and high sulfur fuel oil water accommodated fractions for assessing oil spill effects in marine environments.

The environmental impact of oil spills is a critical concern, particularly pertaining to low sulfur marine diesel (LSMD) and high sulfur fuel oil (HSFO) that are commonly involved in coastal spills. Although transcriptomic biomonitoring of sentinel animals can be a powerful tool for assessing biological effects, conventional methods utilize lethal sampling to examine the liver. As a non-lethal alternative, we have previously shown salmonid caudal fin cyp1a1 is significantly responsive to LSMD-derived toxicants. The present study further investigated the transcriptomic biomonitoring potential of coho salmon smolt caudal fin in comparison to liver tissue in the context of LSMD and HSFO seawater accommodated fraction (seaWAF) exposure in cold-water marine environments. Assessing the toxicity of these seaWAFs involved quantifying polycyclic aromatic hydrocarbon (tPAH50) concentrations and generating gene expression profiles. Initial qPCR analyses revealed significant cyp1a1 response in both liver and caudal fin tissues of both genetic sexes to all seaWAF exposures. RNA-Seq analysis, focusing on the highest LSMD and HSFO seaWAF concentrations (28.4±1.8 and 645.08±146.3 µg/L tPAH50, respectively), revealed distinct tissue-specific and genetic sex-independent transcriptomic responses with an overall enrichment of oxidative stress, cell adhesion, and morphogenesis-related pathways. Remarkably, the caudal fin tissue exhibited transcriptomic response patterns comparable to liver tissue, particularly consistent differential expression of 33 gene transcripts in the liver (independent of sex and oil type) and 44 in the caudal fin. The present work underscores the viability of using the caudal fin as a non-lethal alternative to liver sampling for assessing and tracking oil spill exposure in marine environments.

Dynamic cyp1a1 transcript responses in the caudal fin of coho salmon (Oncorhynchus kisutch) smolts to low sulfur marine diesel water accommodated fraction exposures and depuration.

Oil spills that occur in high traffic coastal environments can have profound consequences for the health of marine ecosystems and the commercial and social interests that are dependent upon these habitats. Given that the global reliance on marine fuels is not abating, it is imperative to develop sensitive and robust tools to monitor oil contamination and remediation in a timely manner. Such tools are increasingly important for ascertaining the immediate and long-term effects of oil contamination on species of interest and local habitats as water-soluble components of oils, such as polycyclic aromatic hydrocarbons (PAHs), can persist post-remediation. We previously demonstrated that 3-methylcholanthrene responsive cytochrome P450-1a (cyp1a1) transcript abundance in the liver and caudal fin of coho salmon smolts (Onchorhynchus kisutch) was sensitive to exposure to low sulfur marine diesel (LSMD) seawater accommodated fractions (seaWAF) in cold water. We expanded upon this paradigm by assessing the utility of the cyp1a1 transcript to track both exposure to LSMD seaWAF and recovery from exposure by measuring cyp1a1 abundance in coho smolts using quantitative polymerase chain reaction (qPCR). Smolts were exposed to either 100 mg/L LSMD seaWAF or clean seawater (control) for 4 days. Fish were then transferred to clean seawater for depuration and tissues sampled at 0, 1, 2, 4, and 8 days from both treatments. Livers and caudal fins were dissected from 40 smolts per group (ntotal = 400 smolts). The LSMD seaWAF-induced cyp1a1 transcript levels significantly decreased one day after depuration in the liver and caudal fin in a sex-independent manner in genotyped females and males. After four days of depuration, cyp1a1 transcript abundance decreased to baseline control levels, regardless of tissue or sex. The present study demonstrates the value of using the caudal fin as a reliable, sensitive, and non-lethal sampling and monitoring tool.

Enhanced marine monitoring and toxicity study of oil spill dispersants including Corexit EC9500A in the presence of diluted bitumen.

Observations made for the analysis of the oil spill dispersant tracer dioctyl sulfosuccinate (DOSS) during LC50 toxicity testing, highlighted a stability issue for this tracer compound in seawater. A liquid chromatography high-resolution quadrupole time-of-flight mass spectrometry (LC/QToF) was used to confirm monooctyl sulfosuccinate (MOSS) as the only significant DOSS breakdown product, and not the related isomer, 4-(2-ethylhexyl) 2-sulfobutanedioate. Combined analysis of DOSS and MOSS was shown to be applicable to monitoring of spill dispersants Corexit® EC9500A, Finasol OSR52, Slickgone NS, and Slickgone EW. The unassisted conversion of DOSS to MOSS occurred in all four oil spill dispersants solubilized in seawater, although differences were noted in the rate of MOSS formation. A marine microcosm study of Corexit EC9500A, the formulation most rapid to form MOSS, provided further evidence of the stoichiometric conversion of DOSS to MOSS under conditions relevant to real world dilbit spill. Results supported combined DOSS and MOSS analysis for the monitoring of spill dispersant in a marine environment, with a significant extension of sample collection time by 10 days or longer in cooler conditions. Implications of the unassisted formation of MOSS and combined DOSS:MOSS analysis are discussed in relation to improving dispersant LC50 toxicity studies.

Evaluation of Gene Bioindicators in the Liver and Caudal Fin of Juvenile Pacific Coho Salmon in Response to Low Sulfur Marine Diesel Seawater-Accommodated Fraction Exposure.

Low sulfur marine diesel (LSMD) is frequently involved in coastal spills and monitoring ecosystem damage, and the effectiveness of cleanup methods remains a challenge. The present study investigates the concentration and composition of polycyclic aromatic hydrocarbons (PAHs) dispersed in LSMD seawater accommodated fractions (WAFs) and assesses the effects of exposure on juvenile coho salmon ( Onchorhynchus kisutch). Three WAFs were prepared with 333, 1067, and 3333 mg/L LSMD. The sum of 50 common PAHs and alkylated PAHs (tPAH50) measured by gas chromatography/triple quadrupole mass spectrometry showed saturation at ∼90 mg/L for all WAFs. These WAFs were diluted 30% for 96 h fish exposures. qPCR was performed on liver and caudal fin from the same genotypically sexed individuals to evaluate PAH exposure, general and oxidative stress, estrogenic activity, and defense against metals. Excluding metal response, our analyses reveal significant changes in gene expression following WAF exposure on juvenile salmon with differential sensitivity between males and females. The 3-methylcholanthrene responsive cytochrome P450-1a ( cyp1a) transcript exhibited the greatest increase in transcript abundance in the caudal fin (10-18-fold) and liver (6-10-fold). This demonstrates that cyp1a is a robust, sex-independent bioindicator of oil exposure in caudal fin, a tissue that is amenable to nonlethal sampling.

Acute toxicity of Corexit EC9500A and assessment of dioctyl sulfosuccinate as an indicator for monitoring four oil dispersants applied to diluted bitumen.

The present study investigated oil dispersant toxicity to fish species typical of the cooler regions of Canada, together with less well-documented issues pertaining to oil dispersant monitoring. The oil dispersant toxicity of Corexit EC9500A was assessed for the freshwater fish species rainbow trout and the seawater species coho, chinook, and chum, with a final median lethal concentration (LC50) acute lethality range between 35.3 and 59.8 mg/L. The LC50 range was calculated using confirmed 0-h dispersant concentrations that were justified by fish mortality within the first 24 h of exposure and by variability of the dispersant indicator dioctyl sulfosuccinate (DOSS) used to monitor concentrations at later time points. To investigate DOSS as an oil dispersant indicator in the environment, microcosm systems were prepared containing Corexit EC9500A, Finasol OSR52, Slickgone NS, and Slickgone EW dispersants together with diluted bitumen. The DOSS indicator recovery was found to be stable for up to 13 d at 5 °C, 8 d at 10 °C, but significantly less than 8 d at ≥15 °C. After 3 d at temperatures ≥15 °C, the DOSS indicator recovery became less accurate and was dependent on multiple environmental factors including temperature, microbial activity, and aeration, with potential for loss of solvents and stabilizers. A final assessment determined DOSS to be a discrepant indicator for long-term monitoring of oil dispersant in seawater. Environ Toxicol Chem 2018;37:1309-1319. © 2018 SETAC.

Biological effects of the anti-parasitic chemotherapeutant emamectin benzoate on a non-target crustacean, the spot prawn (Pandalus platyceros Brandt, 1851) under laboratory conditions.

The potential impact of commercial salmon aquaculture along the coast of British Columbia on the health of non-target marine wildlife is of growing concern. In the current initiative, the biological effects on gene expression within spot prawn (Pandalus platyceros) exposed to the sea lice controlling agent, emamectin benzoate (EB; 0.1-4.8 mg/kg sediment), were investigated. A mean sediment/water partitioning coefficient (K(p)) was determined to be 21.81 and significant levels of EB were detected in the tail muscle tissue in all exposed animals. Animals selected for the experiment did not have eggs and were of similar weight. Significant mortality was observed within 8 days of EB treatment at concentrations between 0.1 and 0.8 mg/kg and there was no effect of EB on molting. Twelve spot prawn cDNA sequences were isolated from the tail muscle either by directed cloning or subtractive hybridization of control versus EB exposed tissues. Three of the transcripts most affected by EB exposure matched sequences encoding the 60S ribosomal protein L22, spliceosome RNA helicase WM6/UAP56, and the intracellular signal mediator histidine triad nucleotide binding protein 1 suggesting that translation, transcription regulation, and apoptosis pathways were impacted. The mRNA encoding the molting enzyme, ß-N-acetylglucosaminidase, was not affected by EB treatment. However, the expression of this transcript was extremely variable making it unsuitable for effects assessment. The results suggest that short-term exposure to EB can impact biological processes within this non-target crustacean.

Acute toxicity of emamectin benzoate and its desmethyl metabolite to Eohaustorius estuarius.

Emamectin benzoate is one of the active ingredients of the anti-sealice drug SLICE. Ten-day acute sediment lethal tests (10-d LC50) of emamectin benzoate and its desmethyl metabolite (AB1) were conducted to determine LC50 values using a sensitive representative West Coast amphipod crustacean, Eohaustorius estuarius. The 10-d LC50s of emamectin benzoate and AB1 to E. estuarius were 0.185 and 0.019 mg/kg wet weight sediment (0.146 and 0.015 mg/kg dry wt), respectively. The degradation properties of emamectin benzoate and AB1 during the 10-d period were also measured and described. No obvious decay patterns were observed for either emamectin benzoate and AB1 over the 10-d period.

Toxicity of alpha-, beta-, (alpha + beta)-endosulfan and their formulated and degradation products to Daphnia magna, Hyalella azteca, Oncorhynchus mykiss, Oncorhynchus kisutch, and biological implications in streams.

The static acute toxicities of alpha-endosulfan, beta-endosulfan, (alpha + beta)-endosulfan, endosulfan sulfate (their transformation product), and formulated materials were determined for a representative freshwater amphipod (Hyalella azteca), cladoceran (Daphnia magna), and salmonid fish (Oncorhynchus mykiss). Acute lethality tests also were conducted on these organisms and coho salmon (Oncorhynchus kisutch) by exposing them to simulated field water endosulfan concentrations, using either a single compound and/or in combinations. As well, growth/survival bioassays of H. azteca were carried out in simulated sediment endosulfan concentrations that were detected in farm ditches contiguous to fish streams in the Lower Fraser Valley (BC, Canada). All materials tested were very highly toxic to these nontarget aquatic indicator organisms. As the most potent compound, alpha-endosulfan is about 1.3, 6.6, and 58 times more toxic than the beta-isomer to Daphnia, rainbow trout, and Hyalella, respectively. Some possible biological and toxicological implications of our findings are discussed in the context of endosulfan concentrations found in farm ditches flowing to fish streams in the Lower Fraser Valley.