A Benford's law-based framework to determine the threshold of occurrence sites for species distribution modelling from ecological monitoring databases.

The use of data-based species distribution models (SDMs) has increased significantly in recent years. However, studies of determining the minimum requirements of occurrence sites from ecological monitoring datasets used in species distribution modelling remain insufficient. Therefore, this study proposed a framework to determine the threshold of minimum occurrence sites for SDMs by assessing compliance with Benford's law. The compliance test verified that the national-scale freshwater fish monitoring dataset was natural and reliable. Results derived from true skill statistics (TSS) determined the minimum number of occurrence sites for reliable species distribution modelling was 20 with a TSS value of 0.793 and an overall accuracy of 0.804. The Benford compliance test has shown to be a useful tool for swift and efficient evaluation of the reliability of species occurrence datasets, or the determination of the threshold of occurrence sites before species distribution modelling. Further studies regarding the evaluation of this method's transferability to other species and validation using SDM performance are required. Overall, the framework proposed in this study demonstrates that Benford compliance test applied to species monitoring datasets can be used to derive a universal and model-independent minimum occurrence threshold for SDMs.

Elevated temperature alleviates benzophenone-3 toxicity in Daphnia magna.

Water temperature rises due to thermal discharge and global warming and the potential resulting impacts on the ecotoxicity of emerging chemicals are a growing concern. Benzophenone-3 (BP-3) is an ultraviolet filter added to personal care and plastic products, which is detected at highest concentrations during the hot summer season. This study aimed to investigate the effect of elevated temperature on acute (48 h) and chronic (21 d) BP-3 toxicity in Daphnia magna. Neonates (<24 h) acclimated at 28 °C showed much lower acute toxicity (EC50 = 3.91 and 2.69 mg L-1 at 20 and 28 °C, respectively) than those acclimated at 20 °C (EC50 = 2.96 and 2.04 mg L-1 at 20 and 28 °C, respectively). The body length, embryonic development, and the number of offspring in D. magna offspring exposed to BP-3 for 21 d were significantly decreased after exposure to 0.8 mg L-1 BP-3 at 20 °C. However, these adverse effects of BP-3 in D. magna were significantly ameliorated at 28 °C. Under these conditions, stress response genes such as Hb (hemoglobin), Hsp70 (heat shock protein), Cyp4 (cytochrome P450), and GST (glutathione-S-transferase) were significantly upregulated. These findings suggest that elevated temperature activated stress responses in D. magna, leading to enhanced protection against BP-3 toxicity. This study will contribute to a better understanding of the ecotoxicological impacts of toxic chemicals on aquatic organisms at elevated temperature.

Evaluation of the combined effect of elevated temperature and cadmium toxicity on Daphnia magna using a simplified DEBtox model.

Thermal discharge and heatwaves under climate change may increase water temperature. In this study, the individual and combined effect of elevated temperature and cadmium (Cd) toxicity on somatic growth and reproduction of Daphnia magna was evaluated using a simplified dynamic energy budget model (DEBtox). The model predicted that the maximum body length (Lm) would be shorter (3.705 mm) at an elevated temperature of 25 °C than at 20 °C (3.974 mm), whereas the maximum reproduction rate (R˙m) would be higher at 25 °C (5.735) than at 20 °C (5.591). The somatic growth and reproduction of D. magna were significantly (p < 0.05) reduced with increasing Cd concentrations, and the reduction was greater at 25 than at 20 °C. Potentiation of Cd toxicity by elevated temperature was correctly simulated by assuming four toxicological modes of action influencing assimilation, somatic maintenance and growth, and reproduction. Overall, the population growth rate of D. magna was expected to decrease linearly with increasing Cd concentrations, and the decrease was expected to be higher at 25 than at 20 °C. These findings suggest a significant ecological risk of toxic metals at elevated temperature, with a mechanistic interpretation of the potentiation effect using a DEBtox modeling approach.

Linking multiple biomarker responses in Daphnia magna under thermal stress.

Temperature is an important abiotic variable that greatly influences the performance of aquatic ectotherms, especially under current anthropogenic global warming and thermal discharges. The aim of the present study was to evaluate thermal stress (20 °C vs 28 °C) in Daphnia magna over 21 d, focusing on the linkage among molecular and biochemical biomarker responses. Thermal stress significantly increased the levels of reactive oxygen species (ROS) and lipid peroxidation, especially in the 3-d short-term exposure treatment. This change in the ROS level was also correlated with mitochondrial membrane damage. These findings suggest that oxidative stress is the major pathway for thermally-induced toxicity of D. magna. Additionally, the expression levels of genes related to hypoxia (Hb), development (Vtg1), and sex determination (Dsx1-α, Dsx1-ß, and Dsx2) were greatly increased by elevated temperature in a time-dependent manner. The cellular energy allocation was markedly decreased at the elevated temperature in the 3-d exposure treatment, mainly due to carbohydrates consumption for survival (oxidative stress defense). The present study showed that linking multiples biomarker responses are crucial for understanding the underlying mechanism of thermal stress on D. magna.

Role of polarity fractions of effluent organic matter in binding and toxicity of silver and copper.

This study evaluates the effect of the physicochemical properties of effluent organic matter (EfOM) from industrial and sewage wastewater treatment plants (WWTPs) on the binding and toxicity of Ag and Cu. EfOM was isolated into hydrophobic, transphilic, and hydrophilic fractions depending on its polarity, and was characterized by elemental, specific ultraviolet absorbance, and fluorescence excitation-emission matrix analyses. Our results suggest that the EfOM consists of microbially derived non-humic substances that have lower aromaticity than the Suwannee River natural organic matter (SR-NOM). The Freundlich model was better at explaining the binding of Ag and Cu onto both SR-NOM and EfOM than the Langmuir model. In particular, the hydrophilic fractions of sewage EfOM showed higher binding capacities and affinities for Ag and Cu than the corresponding hydrophobic fractions, resulting in better reduction of the acute toxicity of Ag and Cu towards Daphnia magna. However, in the case of both SR-NOM and industrial EfOM, the hydrophobic fractions were more efficient at reducing metal toxicity. These findings suggest that the EfOM has different physicochemical properties compared with NOM and that the binding and toxicity of heavy metals are largely dependent on the polarity fractions of EfOM.

Effect of steam activation of biochar produced from a giant Miscanthus on copper sorption and toxicity.

This study aims to evaluate the physiochemical properties, sorption characteristics, and toxicity effects of biochar (BC) produced from Miscanthus sacchariflorus via slow pyrolysis at 500°C and its steam activation product (ABC). Although BC has a much lower surface area than ABC (181 and 322m(2)g(-1), respectively), the Cu sorption capacities of BC and ABC are not significantly different (p>0.05). A two-compartment model successfully explains the sorption of BC and ABC as being dominated by fast and slow sorption processes, respectively. In addition, both BC and ABC efficiently eliminate the toxicity of Cu towards Daphnia magna. However, ABC itself induced acute toxicity to D. magna, which is possibly due to increased aromaticity upon steam activation. These findings suggest that activation of BC produced from M. sacchariflorus at a pyrolytic temperature of 500°C may not be appropriate in terms of Cu sorption and toxicity reduction.

Characterization of cadmium removal from aqueous solution by biochar produced from a giant Miscanthus at different pyrolytic temperatures.

The objective of this study was to investigate the feasibility of biochar for removing Cd from aqueous solution. Biochars were produced from a Miscanthus sacchariflorus via slow pyrolysis at 300, 400, 500 and 600°C. Higher pyrolytic temperature resulted in biochar with a higher aromatic structure and fewer polar functional groups. In particular, pH and surface area of biochar increased greatly at pyrolytic temperatures ≥ 500°C, which increased Cd sorption capacity up to 13.24 mgg(-1). The diffuse-controlled Cd removal was likely due to a surface sorption or a precipitation reaction depending on pH. A simulation with the visual MINTEQ program indicated that the precipitate was Cd(OH)2. In addition, biochar treatment significantly removed the acute toxicity of Cd toward Daphnia magna, resulting in increase of EC50 (50% effective concentration) value from 0.16 to 0.76 mgL(-1).