Quantifying a species thermal tolerance is critical to assessing biological impacts of anticipated increases in temperature (e.g., climate change). Although many studies have documented the critical thermal maximum (CT_max) of fish, there is a paucity of research on thermal biology of sturgeon. The shortnose sturgeon (Acipenser brevirostrum LeSueur, 1818) is a threatened species that exists along the eastern coast of North America. They can be exposed to temperatures ranging from freezing to above 25 °C. Using a heating rate of 6 °C/h, CT_maxand the associated hematological responses of shortnose sturgeon acclimated to 10, 15, and 20 °C were determined. There was a significant positive relationship between CT_maxand body mass, and CT_maxincreased significantly with increases in acclimation temperature (T_a). In general, hematology of thermally stressed fish was modified relative to control (nonstressed) fish. Hematocrit, plasma lactate, and plasma Na⁺and Cl^–of fish were all significantly influenced by thermal stress and T_a. Glucose and K⁺were only significantly influenced by thermal stress. Future studies should address the importance of other stressors, such as salinity and toxicants, on thermal relationships of sturgeon.

The presence of microplastics in the environment and their potential effects on the health of organisms are a subject of great concern. However, with further weathering through UV radiation, mechanical force, and microbiological activity, most of these microplastics will degrade into nano-sized particles with exponentially higher specific surface areas compared to microplastics. Moreover, given that the hydrophobic surface of plastics adsorbs hydrophobic persistent organic pollutants (POPs), the possibility of nano-sized plastic particles potentiating POP sorption has been postulated. We developed a novel radiotracer-based method to investigate the sorption of a model POP, phenanthrene, onto the surface of two different-sized polystyrene nanoplastics (PS-NPs). Using radiotracer analysis, we compared the transport and uptake of ¹⁴C-phenanthrene in zebrafish embryos with two different plastic particle sizes. We also evaluated whether nano-sized plastics altered the toxicity of phenanthrene and the acute sub-lethal responses to phenanthrene in zebrafish embryos. Our results demonstrate that 20 nm PS-NPs have higher sorption capacity for phenanthrene due to increased total surface area per gravimetric mass. Moreover, we demonstrate increased phenanthrene across the chorion and into zebrafish embryos with nano-sized plastics when compared to sub-micron sized plastics. Co-exposure to nano-sized plastics and phenanthrene delayed hatching and induced higher EROD activity in zebrafish embryos when compared to sub-micron sized plastics. The results of our study demonstrate that nano-sized plastics facilitate the transport and uptake of hydrophobic organic pollutants and increase both their bioavailability and potential toxicity to aquatic organisms.

Massive annual production of plastics worldwide, coupled with prolonged environmental degradation and poor recycling policies has resulted in serious concerns regarding the ecological impact of these materials.

The use of nanotechnology to enhance pesticide formulations holds the promise of reduced pesticide use, reduced mobility in soils, and overall improvements in agricultural practices while simultaneously maintaining yields. However, the toxicity of nano-enabled pesticides, including azoxystrobin (Az), has not been well studied compared with their conventional form. This study investigates both lethal and sub-lethal endpoints in zebrafish embryos up to 120 h post-fertilization (hpf) under either laboratory light or simulated UV light. The median lethal concentration (LC50) value of nano-enabled Az (nAz) was significantly lower than the conventional form (Az). Interestingly, artificial UV light significantly increased toxicity (decreased LC50) of both Az and nAz. Malformations were not observed but the remaining yolk sac volume was significantly increased in both types of Az at both light conditions. This decreased yolk consumption is in agreement with reduced oxygen consumption and heart rate. Catalase enzyme activity was only reduced to UV light while superoxide dismutase activity was significantly reduced by co-exposure of UV light, and either type of Az at a nominal concentration of 100 μg L⁻¹. The co-exposure of Az at 100 μg L⁻¹ and UV light significantly upregulated sod1, sod2, and gpx1b expression and both types of Az significantly reduced gpx1a expression. Lipid peroxidation was significantly increased in nAz and Az at 100 μg L⁻¹ under laboratory light, while UV light induced even higher level of lipid peroxidation. The results will provide important information on the toxicity of nAz under ecologically realistic conditions.