Size-Dependent Effects of Micro Polystyrene Particles in the Marine Copepod <i>Tigriopus japonicus</i>

We investigated the effects of three sizes of polystyrene (PS) microbeads (0.05, 0.5, and 6-μm diameter) on the survival, development, and fecundity of the copepod <i>Tigriopus japonicus</i> using acute and chronic toxicity tests. <i>T. japonicus</i> ingested and egested all three sizes of PS beads used and exhibited no selective feeding when phytoplankton were added. The copepods (nauplius and adult females) survived all sizes of PS beads and the various concentrations tested in the acute toxicity test for 96 h. In the two-generation chronic toxicity test, 0.05-μm PS beads at a concentration greater than 12.5 μg/mL caused the mortality of nauplii and copepodites in the <i>F</i>₀ generation and even triggered mortality at a concentration of 1.25 μg/mL in the next generation. In the 0.5-μm PS bead treatment, despite there being no significant effect on the <i>F</i>₀ generation, the highest concentration (25 μg/mL) induced a significant decrease in survival compared with the control population in the <i>F</i>₁ generation. The 6-μm PS beads did not affect the survival of <i>T. japonicus</i> over two generations. The 0.5- and 6-μm PS beads caused a significant decrease in fecundity at all concentrations. These results suggest that microplastics such as micro- or nanosized PS beads may have negative impacts on marine copepods

Styrofoam Debris as a Source of Hazardous Additives for Marine Organisms

There is growing concern over plastic debris and their fragments as a carrier for hazardous substances in marine ecosystem. The present study was conducted to provide field evidence for the transfer of plastic-associated chemicals to marine organisms. Hexabromocyclododecanes (HBCDs), brominated flame retardants, were recently detected in expanded polystyrene (styrofoam) marine debris. We hypothesized that if styrofoam debris acts as a source of the additives in the marine environment, organisms inhabiting such debris might be directly influenced by them. Here we investigated the characteristics of HBCD accumulation by mussels inhabiting styrofoam. For comparison, mussels inhabiting different substrates, such as high-density polyethylene (HDPE), metal, and rock, were also studied. The high HBCD levels up to 5160 ng/g lipid weight and the γ-HBCD dominated isomeric profiles in mussels inhabiting styrofoam strongly supports the transfer of HBCDs from styrofoam substrate to mussels. Furthermore, microsized styrofoam particles were identified inside mussels, probably originating from their substrates

Prediction of Ecotoxicity of Heavy Crude Oil: Contribution of Measured Components

A prediction model for estimating the ecotoxicity of the water-accommodated fraction (WAF) and water-soluble fraction (WSF) of heavy crude oil is proposed. Iranian heavy crude oil (IHC), one of the major components of the Hebei Spirit oil spill in Korea in 2007, was used as a model crude oil for the preparation of the WAF and the WSF. Luminescence inhibition of <i>Vibrio fischeri</i> was chosen as the model ecotoxicity test for evaluating the baseline toxicity of aromatic hydrocarbons in the IHC. The measured concentration of each chemical species in WAF and WSF agreed well with the predicted soluble concentration calculated using Raoult’s law from the measured amount in the IHC. This indicates that the toxic potential of an oil mixture can be evaluated from the dissolved concentration of each species, which in turn, may be predicted from the composition of the crude or weathered oils. In addition, the contribution of each species in the mixture to the apparent luminescence inhibition by the WAF and the WSF was assessed using a concentration-addition model. The relative contributions of benzene, toluene, ethylbenzene, xylenes (BTEX), polycyclic aromatic hydrocarbons (PAHs), and alkylated PAHs in luminescence inhibition were estimated to be 76%, 2%, and 21%, respectively. It was further identified that C3- and C4-naphthalenes were the most important aromatic hydrocarbons responsible for baseline toxicity. This indicates that alkylated PAHs would be the major components of oil-spill residue. Further research is needed to evaluate the fate and ecotoxicity of alkylated PAHs

Large Accumulation of Micro-sized Synthetic Polymer Particles in the Sea Surface Microlayer

Determining the exact abundance of microplastics on the sea surface can be susceptible to the sampling method used. The sea surface microlayer (SML) can accumulate light plastic particles, but this has not yet been sampled. The abundance of microplastics in the SML was evaluated off the southern coast of Korea. The SML sampling method was then compared to bulk surface water filtering, a hand net (50 μm mesh), and a Manta trawl net (330 μm mesh). The mean abundances were in the order of SML water > hand net > bulk water > Manta trawl net. Fourier transform infrared spectroscopy (FTIR) identified that alkyds and poly­(acrylate/styrene) accounted for 81 and 11%, respectively, of the total polymer content of the SML samples. These polymers originated from paints and the fiber-reinforced plastic (FRP) matrix used on ships. Synthetic polymers from ship coatings should be considered to be a source of microplastics. Selecting a suitable sampling method is crucial for evaluating microplastic pollution

Thyroid Hormone Disruption by Water-Accommodated Fractions of Crude Oil and Sediments Affected by the <i>Hebei Spirit</i> Oil Spill in Zebrafish and GH3 Cells

A crude oil and the coastal sediments that were affected by the <i>Hebei Spirit</i> Oil Spill (HSOS) of Taean, Korea were investigated for thyroid hormone disruption potentials. Water-accommodated fractions (WAFs) of Iranian Heavy crude oil, the major oil type of HSOS, and the porewater or leachate of sediment samples collected along the coast line of Taean were tested for thyroid disruption using developing zebrafish and/or rat pituitary GH3 cells. Major polycyclic aromatic hydrocarbons (PAHs) and their alkylated forms were also measured from the test samples. In zebrafish larvae, significant decreases in whole-body thyroxine (T₄) and triiodothyronine (T₃) levels, along with transcriptional changes of thyroid regulating genes, were observed following 5 day exposure to WAFs. In GH3 cells, transcriptions of thyroid regulating genes were influenced following the exposure to the sediment samples, but the pattern of the regulatory change was different from those observed from the WAFs. Composition of PAHs and their alkylated homologues in the WAFs could partly explain this difference. Our results clearly demonstrate that WAFs of crude oil can disrupt thyroid function of larval zebrafish. Sediment samples also showed thyroid disrupting potentials in the GH3 cell, even several years after the oil spill. Long-term ecosystem consequences of thyroid hormone disruption due to oil spill deserve further investigation

Differential Toxicokinetics Determines the Sensitivity of Two Marine Embryonic Fish Exposed to Iranian Heavy Crude Oil

Interspecific difference in the developmental toxicity of crude oil to embryonic fish allows the prediction of injury extent to a number of resident fish species in oil spill sites. This study clarifies the comparative developmental effects of Iranian heavy crude oil (IHCO) on the differences of biouptake and toxic sensitivity between embryonic spotted sea bass (Lateolabrax maculates) and olive flounder (Paralichthys olivaceus). From 24 h after exposure to IHCO, several morphological defects were observed in both species of embryonic fish, including pericardial edema, dorsal curvature of the trunk, developmental delay, and reduced finfolds. The severity of defects was greater in flounder compared to that in sea bass. While flounder embryos accumulated higher embryo PAH concentrations than sea bass, the former showed significantly lower levels of CYP1A expression. Although bioconcentration ratios were similar between the two species for some PAHs, phenanthrenes and dibenzothiophenes showed selectively higher bioconcentration ratios in flounder, suggesting that this species has a reduced metabolic capacity for these compounds. While consistent with a conserved cardiotoxic mechanism for petrogenic PAHs across diverse marine and freshwater species, these findings indicate that species-specific differences in toxicokinetics can be an important factor underlying species’ sensitivity to crude oil

Two Years after the <i>Hebei Spirit</i> Oil Spill: Residual Crude-Derived Hydrocarbons and Potential AhR-Mediated Activities in Coastal Sediments

The <i>Hebei Spirit</i> oil spill occurred in December 2007 approximately 10 km off the coast of Taean, South Korea, on the Yellow Sea. However, the exposure and potential effects remain largely unknown. A total of 50 surface and subsurface sediment samples were collected from 22 sampling locations at the spill site in order to determine the concentration, distribution, composition of residual crudes, and to evaluate the potential ecological risk after two years of oil exposure. Samples were extracted and analyzed for 16 polycyclic aromatic hydrocarbons (PAHs), 20 alkyl-PAHs, 15 aliphatic hydrocarbons, and total petroleum hydrocarbons using GC-MSD. AhR-mediated activity associated with organic sediment extracts was screened using the H4IIE-<i>luc</i> cell bioassay. The response of the benthic invertebrate community was assessed by mapping the macrobenthic fauna. Elevated concentrations of residual crudes from the oil spill were primarily found in muddy bottoms, particularly in subsurface layers. In general, the bioassay results were consistent with the chemistry data in a dose-dependent manner, although the mass-balance was incomplete. More weathered samples containing greater fractions of alkylated PAHs exhibited greater AhR activity, due to the occurrence of recalcitrant AhR agonists present in residual oils. The macrobenthic population distribution exhibits signs of species-specific tolerances and/or recolonization of certain species such as <i>Batillaria</i> during weathering periods. Although the <i>Hebei Spirit</i> oil spill was a severe oil exposure, it appears the site is recovering two years later