Toxicity of fuels and dispersants to the Antarctic marine nemertean Antarctonemertes unilineata

Brief description

This metadata record contains the results from bioassays conducted to show the response of an Antarctic nemertean Antarctonemertes unilineata to contamination from combinations of Special Antarctic Blend (SAB) diesel, Marine Gas Oil (MGO) and Intermediate Fuel Oil (IFO 180), chemically dispersed with fuel dispersants Ardrox 6120, Slickgone LTSW and Slickgone NS. Note that the corresponding PhD thesis chapter refers to the species as Antarctonemertes sp., prior to being named Antarctonemertes unilineata in 2018.

Experiments using SAB, MGO and IFO 180 with the dispersant Ardrox 6120, including fuel only and dispersant only treatments were conducted at Casey station. Experiments involving IFO 180 and the fuel dispersants Slickgone LTSW and Slickgone NS were conducted at the Antarctic Division’s Marine Research Facility quarantine labs. All experimental procedures, including test mix preparation and bioassays were conducted at 0 plus or minus 1 degree C. Water accommodated fractions (WAF; fuel mixed in water) and chemically enhanced water accommodated fractions (CEWAF) were made according to the specifications of Singer, Aurand et al. (2000), Barron and Ka’aihue (2003) and Kotzakoulakis (unpublished at time of writing). Dispersant only mixes were also made using filtered seawater (FSW) and dispersant volumes proportional to those used for CEWAF production. WAF was made using a loading ratio of 1: 25 (v/v) fuel to FSW, CEWAF was prepared using 1:100 (v/v) fuel to FSW ratio, and 1: 20 (v/v) dispersant to fuel ratio. Following the 48 h preparation time, the seawater WAF components of the mix were drained from the bottom of aspirator bottles and serially diluted. WAF treatment concentrations were 100%, 50%, 20% and 10%, CEWAF and dispersant only concentrations were 10%, 5%, 1% and 0.1%. Treatment solutions were replenished every four days to simulate a repeated pulse exposure to contaminants and to replace hydrocarbons lost through evaporation and adsorption and to maintain water quality parameters. WAF, CEWAF and dispersant only test solutions were remade every four days using identical methods.

Tests were done in temperature-controlled cabinets set to 0 plus or minus 1 degree C following a 6 h light to 18 h dark photoperiod. Beakers were left uncovered to allow for the natural evaporation of lighter hydrocarbon components to reflect real fuel spill conditions. Experiments ran for 24 d except for the Ardrox 6120 only experiment, which ran for 16 d due to high mortality in this treatment. Sublethal and lethal endpoints were assessed at 1, 2, 4, 7, 8, 12, 14, 16, 20 and 24 d observations.

Aliquot water samples for analysis of total hydrocarbon content (THC) were taken for initial and final test concentrations, and before and after each four-day water change, to obtain accurate profiles of hydrocarbon loss over the test period. Duplicate samples were taken for every treatment concentration and extracted with dichloromethane, spiked with an internal standard of 1-bromoeicosane and cyclooctane. Samples were analysed using gas chromatography with flame ionization detection (GC-FID) and gas chromatography mass spectrometry (GC-MS). Average THC concentrations for the duration of the experiment were obtained by integrating the measured concentrations to which animals were exposed following the methods of Brown et al. (2016) and Payne et al. (2014).

This data submission includes one file detailing the TPH experiment analyses and one detailing the bioassay tests and results. The thesis that relates to this work is available from: https://epubs.scu.edu.au/theses/533/

Lineage

Progress Code: completed

Statement: Contamination of hydrocarbon samples when taken for analysis increased difficulty and decreased accuracy of total petroleum hydrocarbon content analysis of samples.

The lowest concentrations of 0.1% for chemically dispersed CEWAF contained THC levels below reliable detection limits of the equipment used, therefore 0.1% concentrations were extrapolated based on measured 1% THC concentrations.

Analyses of dispersant only treatments using GC-FID were found to be quantitatively unreliable due to imperfect extraction of large amounts of non-hydrocarbon molecules. Dispersant calculations were instead performed based on nominal loading in μL/L, based on the assumption that all dispersants are highly water soluble and therefore likely to be fully incorporated into the water column.

Notes

Purpose
Assessing the toxicity of the water accommodated fractions of three fuels, Special Antarctic Blend diesel (SAB), marine gas oil (MGO) and intermediate fuel oil (1FO 180) and three dispersants Ardrox 6120, Slickgone LTSW and Slickgone NS to an Antarctic nemertean, Antarctonemertes unilineata.