Oil droplet fouling and differential toxicokinetics of polycyclic aromatic hydrocarbons in embryos of Atlantic haddock and cod

Abstract

The impact of crude oil pollution on early life stages (ELS) of fish, including larvae and embryos, has received considerable attention in recent years. Of the organic components present in crude oil, polycyclic aromatic hydrocarbons (PAHs) are considered the main class of compounds responsible for toxic effects in marine organisms. Although evidence suggests that they are more toxic, alkylated PAHs remain much less studied than their unsubstituted congeners. Recently, it was established that embryos of Atlantic haddock (Melanogrammus aeglefinus) are particularly sensitive to dispersed crude oil, and it was hypothesized that this was caused by direct interaction with crude oil droplets, which adhered to the chorion of exposed embryos. Such a phenomenon would increase the potential for uptake of less water-soluble compounds, including alkylated PAHs. In the current study, we compared the uptake of parent and alkylated PAHs in Atlantic cod (Gadus morhua) and haddock embryos exposed to dispersed crude oil at a range of environmentally relevant concentrations (10–600 μg oil/liter seawater). Although the species are biologically very similar, the cod chorion does not become fouled with oil droplets, even when the two species are exposed to dispersions of crude oil droplets under similar conditions. A close correlation between the degree of fouling and toxicological response (heart defects, craniofacial malformation) was observed. Oil droplet fouling in haddock led to both quantitative and qualitative differences in PAH uptake. Finally, kinetic data on a large suite of PAHs showed differential elimination, suggesting differential metabolism of unsubstituted versus alkylated compounds.

Toxicities of Polycyclic Aromatic Hydrocarbons for Aquatic Animals

“…The mean diameters of retinal layers and optomotor response were significantly reduced in oil-exposed larvae [60]. Embryos particularly sensitive to dispersed crude oil have been reported [61]. The embryos of Atlantic haddock (Melanogrammus aeglefinus) were fouled by crude oil droplets adhering to the chorion when exposed to concentrations of more than 0.7 µg/L tPAH [61].…”

“…Embryos particularly sensitive to dispersed crude oil have been reported [61]. The embryos of Atlantic haddock (Melanogrammus aeglefinus) were fouled by crude oil droplets adhering to the chorion when exposed to concentrations of more than 0.7 µg/L tPAH [61]. This correlated with an increase in toxicological responses (malformations and cardiotoxicity).…”

Oil toxicity test methods must be improved

“…Chemical analyses are not without error. Only dissolved hydrocarbons appear to be bioavailable and toxic to some species (Carls et al ; Redman et al ), although oil droplets adhering to eggs of Atlantic haddock ( Melanogrammus aeglefinus ) coincided with a greater uptake of PAC, and a higher sensitivity to oil exposure than eggs of Atlantic cod ( Gadus morhua ; Sørhus et al ; Sørensen et al ). Oil droplets in test solutions will be combined with dissolved oil in total oil when water samples are extracted with solvents for TPH and PAC analyses, or when samples for TPH‐F analyses are preserved with ethanol.…”

Ecological Effects and Ecosystem Shifts Caused by Mass Mortality Events on Early Life Stages of Fish

“…Previous studies have limited their scope to a single species, i.e., cod, which seems to be more resilient to oil than its sibling species haddock (Sørensen et al, 2017). Adding to this the different life histories and recruitment patterns (Olsen et al, 2010) for cod, herring and haddock leads to overlooking speciesspecific and ecological responses that become apparent when investigating the effects of MMEs using end-to-end ecosystem models.…”