Coastal and marine pollution and ecotoxicology

Synergistic effect of chloroquine and copper to the euryhaline rotifer Proales similis

Chloroquine (CQ) has been widely used for many years against malaria and various viral diseases. Its important use and high potential to being persistent make it of particular concern for ecotoxicological studies. Here, we evaluated the toxicity of CQ alone and in combination with copper (Cu) to the euryhaline rotifer Proales similis. All experiments were carried out using chronic toxicity reproductive five-day tests and an application factor (AF) of 0.05, 0.1, 0.3, and 0.5 by multiplying the 24-h LC₅₀ values of CQ (4250 µg/L) and Cu (68 µg/L), which were administered in solution. The rate of population increase (r, d^-1) ranged from 0.50 to 52 (controls); 0.20 to 0.40 (CQ); 0.09 to 0.43 (Cu); and -0.03 to 0.30 (CQ-Cu) and showed significant decrease as the concentration of both chemicals in the medium increased. Almost all tested mixtures induced synergistic effects, mainly as the AF increased. We found that the presence of Cu intensifies the vulnerability of organisms to CQ and vice versa. These results stress the potential hazard that these combined chemicals may have on the aquatic systems. This research suggests that P. similis is sensitive to CQ as other standardized zooplankton species and may serve as a potential test species in the risk assessment of emerging pollutants in marine environments.

Enhanced degradation of different crude oils by defined engineered consortia of Acinetobacter venetianus RAG-1 mutants based on their alkane metabolism

Microbial consortia offer an attractive biodegradation strategy for removing hydrocarbons from oil-contaminated sites. In this study, we explored the degradation properties of Acinetobacter venetianus strain RAG-1 (RAG-1). RAG-1 effectively degrades three crude oils with excellent emulsification activity and cell surface hydrophobicity, while exhibiting broad environmental tolerance. RAG-1 accepts a range of alkane substrates (C₁₀-C₃₈) using three alkane hydroxylases (AlkMa, AlkMb, and AlmA). Bacterial mutant with alkMa or alkMb deletion enhanced degradation of C₁₀-C₂₀ or C₂₂-C₃₂ n-alkanes, respectively. Based on the substrate metabolism of the mutants, adjustable and targeted consortia consisting of ΔalkMa/almA and ΔalkMb were constructed, achieving enhanced degradation (10 days) of light crude oil (73.42% to 88.65%), viscous crude oil (68.40% to 90.05%), and high waxy crude oil (47.46% to 60.52%) compared with the single wild-type strain. The degradation properties of RAG-1 and the engineered consortia strategy may have potential use in microbial biodegradation applications.

Marine coastal ecosystem and ecotoxicology

Environmental pollution from industrialization, urbanization and agriculture is a serious issue facing all countries during economic development. The Pearl River Delta in Southern China offers a unique case for study and documentation on the ecosystem changes during the fast economic development and urbanization over the past 40 years. This collection of papers from a conference on marine coastal pollution and ecotoxicology held in Guangzhou of China provide the current status on the environmental and ecological processes from the intensive urbanization and development. The research information available from this special issue can be used for both a comparison over time and with other locations and countries, and, in addition, for policy making to serve the long-term sustainable development of the region and the world.

Biomarker and histopathological responses of Lates calcarifer on exposure to sub lethal concentrations of chlorpyrifos

Bioassay tests on fingerlings (3.0 ± 0.5cm) of euryhyaline fish Lates calcarifer were conducted using customized continuous flow through system and derived 96h acute toxicity value for chlorpyrifos (CPF). Based on the measured concentration of CPF mean median lethal concentration (LC₅₀) of 1.07µg/l with lower and upper 95% confidence limits (0.95 and 1.19µg/l). No observed Effect Concentration (NOEC), Lowest Observed Effect Concentration (LOEC) and chronic values were found to be 0.4, 0.09 and 0.07µg/l respectively. Key biomarker enzyme activities such as esterase, superoxide dismutase and malate dehydrogenase were measured in whole body tissues of the fish fingerlings on exposure to sublethal toxicity of CPF resulting in inhibition of enzyme activities. Native gel electrophoresis revealed single isoform of SOD and MDH enzyme activities exhibiting time and concentration dependent inhibition. Interestingly, three isoforms of esterase activity were witnessed, two isoforms didn't show changes and one isoform was completely inhibited. The observed changes indicated continuous production of reactive oxygen species (ROS) in cells, affecting the integrity and function of cell membrane. Decreased MDH activity indicates reduction of ATP production in the mitochondria leading to susceptibility of fish fingerlings due to the imposed CPF toxicity. Histopathological changes are evident as physiological signatures of chemical interactions in the cell and are prominently used for the evaluation of toxic effects. Gills and eye tissues were selected considering the possible effects on respiratory surfaces and vision impairment. Their tissue sections were observed for changes in primary & secondary lamellae, and retina of the eye respectively. Prominent pathological lesions of gills and retina of the eye include degeneration of cells, fusion, lifting of epithelium and increased cellular space, detachment of pigment epithelium, fusion of photoreceptor cells, respectively on exposure to 30 days of sub lethal concentrations. CPF was found to be highly toxic, affecting the vital functions of respiration, vision and cellular activities leading to susceptibility of fish fingerlings.