Comparison of biomarker responses following one dose of benzo-a-pyrene administered to three native Australian fish species

The Australian native fish pink snapper (Pagrus auratus Forster) is currently used as a bioindicator species for laboratory and field studies, but is often unavailable from hatcheries, or collected in limited numbers in the field. Consequently, mulloway (Argyrosomus hololepidotus Lacepede) and barramundi (Lates calcarifer Bloch), two Australian native fish species, were tested in an exploratory study as potential bioindicator surrogates to pink snapper. Experimental fish were i.p. injected with benzo(a)pyrene (BaP), a well known biomarker inducer in fish, at a dose of 1.0f. µg/g of fish. Physiological indices i.e. condition factor (CF) and liver somatic index (LSI) and a suite of biomarkers including ethoxyresorufin-0-deethylase (EROD) activity, biliary metabolites, serum sorbitol dehydrogenase (SOH), DNA damage (Comet assay) and heat shock proteins HSP 70 were explored in the three test species. Mulloway and barramundi showed a higher response in biliary metabolite levels than pink snapper, while pink snapper showed a higher EROD induction potential relative to mulloway and barramundi. Mulloway appeared to be sensitive to hepatotoxicants, as the chemical injury sustained by the liver resulted in the release of SOH in the bloodstream of this species. All three species were significantly responsive to DNA damage. When injected with BaP, the three species showed similar response for CF, LSI and HSP 70. Initial results indicate that mulloway and barramundi are suitable surrogate bioindicator species for pink snapper in relation to exposure to BaP

Induction of fish biomarkers by synthetic-based drilling muds

The study investigated the effects of chronic exposure of pink snapper (Pagrus auratus Forster), to synthetic based drilling muds (SBMs). Fish were exposed to three mud systems comprised of three different types of synthetic based fluids (SBFs): an ester (E), an isomerized olefin (IO) and linear alpha olefin (LAO). Condition factor (CF), liver somatic index (LSI), hepatic detoxification (EROD activity), biliary metabolites, DNA damage and stress proteins (HSP-70) were determined. Exposure to E caused biologically significant effects by increasing CF and LSI, and triggered biliary metabolite accumulation. While ester-based SBFs have a rapid biodegradation rate in the environment, they caused the most pronounced effects on fish health. IO induced EROD activity and biliary metabolites and LAO induced EROD activity and stress protein levels. The results demonstrate that while acute toxicity of SBMs is generally low, chronic exposure to weathering cutting piles has the potential to affect fish health. The study illustrates the advantages of the Western Australian government case-by-case approach to drilling fluid management, and highlights the importance of considering the receiving environment in the selection of SBMs

Toxicity assessment of individual ingredients of synthetic-based drilling muds (SBMs)

Synthetic-based drilling muds (SBMs) offer excellent technical characteristics while providing improved environmental performance over other drilling muds. The low acute toxicity and high biodegradability of SBMs suggest their discharge at sea would cause minimal impacts on marine ecosystems, however, chronic toxicity testing has demonstrated adverse effects of SBMs on fish health. Sparse environmental monitoring data indicate effects of SBMs on bottom invertebrates. However, no environmental toxicity assessment has been performed on fish attracted to the cutting piles. SBM formulations are mostly composed of synthetic base oils, weighting agents, and drilling additives such as emulsifiers, fluid loss agents, wetting agents, and brine. The present study aimed to evaluate the impact of exposure to individual ingredients of SBMs on fish health. To do so, a suite of biomarkers [ethoxyresorufin-O-deethylase (EROD) activity, biliary metabolites, sorbitol dehydrogenase (SDH) activity, DNA damage, and heat shock protein] have been measured in pink snapper (Pagrus auratus) exposed for 21 days to individual ingredients of SBMs. The primary emulsifier (Emul S50) followed by the fluid loss agent (LSL 50) caused the strongest biochemical responses in fish. The synthetic base oil (Rheosyn) caused the least response in juvenile fish. The results suggest that the impact of Syndrill 80:20 on fish health might be reduced by replacement of the primary emulsifier Emul S50 with an alternative ingredient of less toxicity to aquatic biota. The research provides a basis for improving the environmental performance of SBMs by reducing the environmental risk of their discharge and providing environmental managers with information regarding the potential toxicity of individual ingredients. © 2011 Springer Science+Business Media B.V

Improvements to the Environmental Performance of Synthetic-Based Drilling Muds

Drilling muds used by the petroleum exploration and production industry have the role of lubricating and cooling the drilling bits and facilitating the transport of crushed rocks to the surface of the well. The chemical formulations of the drilling muds influence their fate when discharged into the marine environment and, along with ambient parameters, determine the biodegradability and toxicity of the muds. A case study describes the comparison of aquatic toxicity and biodegradability of two different synthetic-based drilling mud systems (SBMs), Syndrill 80:20 and Syndrill 90:10, and also individual mud ingredients. Chronic fish toxicity was measured using a suite of biomarkers of fish health. Preliminary tests led to the selection of the drilling mud Syndrill 80:20, and toxicity testing of individual ingredients of this mud showed that the primary emulsifier was the most aggressive component among all the mud ingredients tested. The present study aimed at developing an ecologically safe, green SBM by further improvements to Syndrill 80:20 through replacement of the most aggressive emulsifier with an alternative low/non-toxic alternative.The existing Syndrill 80:20 formulation was re-engineered by the incorporation of two alternative emulsifiers as replacements for the existing aggressive emulsifier. The new modified Syndrill 80:20 was then evaluated for its chronic toxicity against the existing Syndrill 80:20 using a suite of biomarkers of fish health. Following exposure to the modified mud system, pink snapper (Pagrus auratus) demonstrated weaker biological reactions as measured by ethoxyresorufin-O-deethylase (EROD) activity, biliary metabolites, and serum sorbitol dehydrogenase (SDH) activity. Closed-bottle biodegradation tests also indicated that the new formulation is actively biodegrading under marine anaerobic conditions. Therefore, the information on the toxicity of the re-engineered SBM provides an initial basis for evaluating its environmental performance in marine ecosystems, and may assist regulatory authorities in gaining a better understanding of the fate of SBMs in the marine environment

Stress proteins HSP-70 (pixels/mg pr, mean ± SEM) measured in pink snapper exposed to E: ester; IO: isomerised olefin; and LAO: linear alpha olefin SBMs.

<p>* indicates statistically different from negative control fish.</p

EROD activity (pmol resorufin/mg pro/min, mean ± SEM) in pink snapper exposed to 5% v/v synthetic-based drilling muds for 28 days.

<p>* indicates statistically different from negative control fish.</p

Physiological parameters for juvenile pink snapper exposed to ester, internal olefins, and linear alpha olefins-based drilling muds for 28 days.

<p>N = 8 per treatment.</p>*<p>indicates a significant difference (p<0.05) relative to negative control group.</p

Physicochemical parameters of the seawater during the acclimation (n = 14 days) and experimental (n = 28 days) periods.

<p>Physicochemical parameters of the seawater during the acclimation (n = 14 days) and experimental (n = 28 days) periods.</p

DNA damage (F-value, mean ± SEM) measured in pink snapper exposed to E: ester; IO: isomerised olefin; and LAO: linear alpha olefin SBMs.

<p>* indicates statistically different from negative control fish.</p

Analysis of water samples of Ester, Internal Olefins and Linear Alpha Olefins based SBMs and Negative Control treatments in which juvenile pink snappers were exposed.

<p>Analysis of water samples of Ester, Internal Olefins and Linear Alpha Olefins based SBMs and Negative Control treatments in which juvenile pink snappers were exposed.</p