Effects of crude oil exposure on bioaccumulation of polycyclic aromatic hydrocarbons and survival of adult and larval stages of gelatinous zooplankton

Abstract

Gelatinous zooplankton play an important role in marine food webs both as major consumers of metazooplankton and as prey of apex predators (e.g., tuna, sunfish, sea turtles). However, little is known about the effects of crude oil spills on these important components of planktonic communities. We determined the effects of Louisiana light sweet crude oil exposure on survival and bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in adult stages of the scyphozoans Pelagia noctiluca and Aurelia aurita and the ctenophore Mnemiopsis leidyi, and on survival of ephyra larvae of A. aurita and cydippid larvae of M. leidyi, in the laboratory. Adult P. noctiluca showed 100% mortality at oil concentration ≥20 µL L(-1) after 16 h. In contrast, low or non-lethal effects were observed on adult stages of A. aurita and M. leidyi exposed at oil concentration ≤25 µL L(-1) after 6 days. Survival of ephyra and cydippid larva decreased with increasing crude oil concentration and exposition time. The median lethal concentration (LC50) for ephyra larvae ranged from 14.41 to 0.15 µL L(-1) after 1 and 3 days, respectively. LC50 for cydippid larvae ranged from 14.52 to 8.94 µL L(-1) after 3 and 6 days, respectively. We observed selective bioaccumulation of chrysene, phenanthrene and pyrene in A. aurita and chrysene, pyrene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo[a]anthracene in M. leidyi. Overall, our results indicate that (1) A. aurita and M. leidyi adults had a high tolerance to crude oil exposure compared to other zooplankton, whereas P. noctiluca was highly sensitive to crude oil, (2) larval stages of gelatinous zooplankton were more sensitive to crude oil than adult stages, and (3) some of the most toxic PAHs of crude oil can be bioaccumulated in gelatinous zooplankton and potentially be transferred up the food web and contaminate apex predators.

Figure 1. Temporal variation of the survival (%) of ephyra larvae of the scyphozoan Aurelia aurita (A) and cydippid larvae of the ctenophore Mnemiopsis leidyi (B) exposed to different concentrations of crude oil (µL L⁻¹).

Symbols show the average values of mortality and error bars represent the standard errors.

Figure 2. Relationships between mortality (%) of ephyra larvae of the scyphozoan Aurelia aurita and crude oil concentration after 24 (A), 48 (B) and 72 (C) hours of exposure.

Regression lines based on Equation (1).

Figure 3. Relationships between mortality (%) of cydippid larvae of the ctenophore Mnemiopsis leidyi and crude oil concentration after 3 (A), 4 (B), 5(C) and 6 (D) days of exposure.

Regression lines based on Equation (1).

Figure 4. Relationships between median lethal concentration (LC₅₀, µL L⁻¹) and incubation time (t, hours) of ephyra larvae of the scyphozoan Aurelia aurita (A) and cydippid larvae of the ctenophore Mnemiopsis leidyi (B) exposed to crude oil.

Figure 5. Total concentration of the polycyclic aromatic hydrocarbons (total PAHs) detected in adult stages of scyphozoan Aurelia aurita (A) and the ctenophore Mnemiopsis leidyi (B) after 6 days of exposure to different concentrations of crude oil.

(Control: no oil, E1: 1 µL L⁻¹, E2: 5 µL L⁻¹, E3: 25 µL L⁻¹.) Error bars represent the standard errors.

Figure 6. Concentration of the main polycyclic aromatic hydrocarbons detected in adult stages of scyphozoan Aurelia aurita after 6 days of exposure to different crude oil concentrations.

(Control: no oil, E1: 1 µL L⁻¹, E2: 5 µL L⁻¹, E3: 25 µL L⁻¹.) Error bars represent the standard errors.

Figure 7. Concentration of the main polycyclic aromatic hydrocarbons (PAHs) detected in adult stages of ctenophore Mnemiopsis leidyi after 6 days of exposure to different crude oil concentrations.

(Control: no oil, E1: 1 µL L⁻¹, E2: 5 µL L⁻¹, E3: 25 µL L⁻¹.)