Oil spill is a major marine environmental pollution issue. Research regarding the long-term effects of oil spills on the early life stage of marine fish is still limited. In this study, the potential adverse impact of crude oil from one oil spill accident which occurred in the Bohai Sea on the early life stages of marine medaka (Oryzias melastigma, McClelland, 1839) was evaluated. A 96-h acute test (larvae) and a 21-d chronic test (embryo–larvae) of water-accommodated fractions (WAFs) from crude oil were conducted, respectively. The results of the acute test showed that only the highest concentration of WAFs (100.00%) significantly affected the mortality of larvae (p < 0.01) and that the 96 h-LC₅₀ was 68.92% (4.11 mg·L^-1 expressed as total petroleum hydrocarbons (TPHs)). Larval heart demonstrated histopathological alterations in all WAF-exposed groups. The chronic test results showed that, except for larval mortality, the total hatching success (%)/hatching time of embryos in WAF treatments was not significantly different from those of the control group (p > 0.05), and no malformation was found in surviving larvae after 21 d of exposure. Nevertheless, the exposed embryos and larvae in the highest concentration of WAFs (60.00%) demonstrated significantly reduced heart rate (p < 0.05) and increased mortality (p < 0.01), respectively. Overall, our results indicated that both acute and chronic WAF exposures had adverse impacts on the survival of marine medaka. In the early life stages, the heart of the marine medaka was the most sensitive organ which showed both structural alteration and cardiac dysfunction.

Micro and nanoplastics (MNPs) as emerging contaminants have become a global environmental issue due to their small size and high bioavailability. However, very little information is available regarding their impact on zooplankton, especially when food availability is a limiting factor. Therefore, the present study aims at evaluating the long-term effects of two different sizes (50 nm and 1 μm) of amnio-modified polystyrene (PS-NH₂) particles on brine shrimp, Artemia parthenogenetica, by providing different levels of food (microalgae) supply. Larvae were exposed to three environmentally relevant concentrations (5.5, 55, and 550 μg/L) of MNPs over a 14-days of exposure with two food levels, high (3 × 10⁵~1 × 10⁷ cells/mL), and low (1 × 10⁵ cells/mL) food conditions. When exposed to high food levels, the survival, growth, and development of A. parthenogenetica were not negatively affected at the studied exposure concentrations. By comparison, when exposed to a low food level, a U shape trend was observed for the three measured effects (survival rate, body length, and instar). Significant interactions between food level and exposure concentration were found for all three measured effects (three-way ANOVA, p < 0.05). The activities of additives extracted from 50 nm PS-NH₂ suspensions were below toxic levels, while those from 1-μm PS-NH₂ showed an impact on artemia growth and development. Our results demonstrate the long-term risks posed by MNPs when zooplankton have low levels of food intake.