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.
Highlights
Petroleum or crude oil is one of the most common pollutants released into the marine environment [1]
Survival of adult stages of the ctenophore Mnemiopsis leidyi was not affected by crude oil at concentrations #5 mL L21, but decreased to 79% at 25 mL L21 after 6 days of exposure (Table 3)
According to our results and considering the median lethal concentrations of crude oil or water soluble fraction commonly observed in zooplankton, adult Aurelia aurita and M. leidyi showed much higher tolerance to crude oil or petroleum hydrocarbons than other zooplankton, such as copepods [8,16,31,75,76,77,78], fish larvae [79,80], and other invertebrates [81,82,83]
Summary
Petroleum or crude oil is one of the most common pollutants released into the marine environment [1]. Among the biological components of marine ecosystems, planktonic organisms are susceptible to crude oil pollution [6,7,8]. Small crude oil droplets (1–100 mm in diameter) generated by wind and waves and or by treatment with chemical dispersants are effectively suspended in the water column [9,10,11]. These crude oil droplets, which are frequently in the food size spectra of many zooplankters, can interact with planktonic organisms. Given the key role of zooplankton in marine food web dynamics, biogeochemical cycling and fish recruitment [22,23,24], knowledge of the interactions between crude oil and zooplankton is crucial for our understanding of the fate of crude oil in the pelagic zone and the impact of oil spills in marine environments
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