Abstract
Macondo source oils and artificially weathered oil residues from 150 °C+ to 300 °C+, including artificially photo oxidized oils, were prepared and used for generating low energy water accommodated fractions (LE-WAFs) in order to assess the impact of oil weathering on WAF chemistry composition and toxicity to marine organisms. Two pelagic species representing primary producers (the marine algae Skeletonema pseudocostatum) and invertebrates (the marine copepod Acartia tonsa) were tested. Obtained acute toxicity levels, expressed as EC/LC50 values, were in the same range or above the obtained maximum WAF concentrations for WAFs from most weathering degrees. Based on % WAF dilutions, reduced toxicity was determined as a function of weathering. The chemical compositions of all WAFs were compared to compositions obtained from water samples reported in the GRIIDC database using multivariate analysis, indicating that WAFs of photo oxidized and two field weathered oils resembled the field data the most.
Highlights
Assessing the environmental effects of accidental releases of crude oil to the marine environment is a complex process
We investigated the environ mental relevance of our laboratory prepared water accommodated fraction (WAF) by comparing compositional data with field collected water samples provided in the Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC) using principal component analysis (PCA)
The maximum total concentration in WAFs decreased with increased artificial weathering of the oil, ranging from 4 mg/L in WAF from fresh Source oil to 0.16 mg/L in WAF of the 300 Cþ residue
Summary
Assessing the environmental effects of accidental releases of crude oil to the marine environment is a complex process. The exposure scenarios for marine organisms become highly dynamic. Many components in crude oils are considered toxic and their environmental effects dependent on envi ronmental concentration as well as on their bioavailability. Dissolved components are considered more bioavailable and more acutely toxic than components residing in dispersed oil droplets (Hansen et al, 2009, 2018b). Oil exposure can cause a variety of adverse effects in marine copepods such as narcosis (Hansen et al, 2012, 2016), altered growth and development (Toxværd et al, 2018) and reduced fecundity (Hansen et al, 2015; Olsen et al, 2013) in marine copepods
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