Eco-toxicology has been the basis for research on the physical and chemical properties of pollutants. Our research team has helped to clarify the interactions between toxic substances and organisms and subsequent changes in the development of target organisms caused by pollutants at the molecular level, in order to discover possible pathways of toxic pollutants and the mechanisms of their toxicity. In addition, we have focused on molecular biomarkers and variations in gene expressions to assess the toxicity of persistent organic pollutants in the soil. This represents a new trend in ecological toxicology.
Biomarkers of eco-toxicological effects of pollutants. Toxicological processes and effects of pollutants on organisms form the basis for identifying hazardous materials in ecosystems. At the same time, research on ecotoxicology as a basis for soil bioremediation has been limited. Our research has focused on the toxicological effects of pollutants on plants and animals in terrestrial and aquatic ecosystems. We have established new molecular biomarkers to investigate the toxicological effects and environmental risks of pollutants and to reveal the pathways and mechanisms of these toxic pollutants.
Our studies on PAH-contaminated soils have revealed the mechanisms and the toxicological effects of PAHs on soil organisms. We found that benzopyrene exerts a significant impact on the gene expression of annetocin and TCTP in earthworms. This may clearly affect the reproduction of earthworms and increases the risk of cancer. In this light, earthworms are more sensitive for use as an environmental indicator than are the macroscopic observation indices. Using the earthworm TCTP gene as a molecular marker, we are able to evaluate the ecological risks of pollutants to soil biota.
We have also examined the effects of low concentrations of PAHs on earthworms with respect to physiological responses such as energy metabolism, degradation and detoxification, signal transduction, protein synthesis and repair, apoptosis and reproductive ovulation. We were the first to find multi-differential expression genes in earthworms, which provide the bases for the toxicity mechanism induced by low concentration PAHs. We have also identified alternative molecular markers for soil pollution monitoring using the earthworm as a model organism.
Aquatic ecotoxicology of heavy metals. Research on the ecotoxicology of heavy metals and other contaminants has focused on their effects on aquatic organisms at different biological levels, as well as the cascading effects of contaminants along the food chain. Heavy metals exert strong selection pressure on biotic populations found in sites polluted by metal mining, smeltering, or other anthropogenic activities. At the population level, when assessing the chronic effects of contaminants on natural populations, the potential for the evolution of resistance due to natural selection should be taken into account. Our results showed that the least killifish (Heterandria formosa) rapidly developed resistance to cadmium. Many aquatic organisms have developed great diversity in morphology, life history traits and physiological characteristics during their long and complex evolution. At the organism level, the biodynamic model of bioaccumulation (DYMBAM) uses experimentally-derived species-specific rate constants (i.e., uptake and efflux rate) that take into account differences in how aquatic animals react internally to metals. Utilizing both laboratory data and field observations, this model helps explain why species differ in magnitude and patterns of metal bioaccumulation and why bioaccumulation differs widely for different metals. Our results have shown that physiological traits in aquatic insects may determine their susceptibility to heavy metal pollution. Aquatic organisms can take up metals from both water and their diets. We have demonstrated that dietary exposure is a dominant route for metal accumulation in the mayfly (Centreptilum triangulifer). Primary producers (i.e., algae and diatoms) can take up and magnify metals, creating magnification factors along the food chain ranging from 103 to 107. Metals accumulated in lower trophic level species can be transferred to organisms at high trophic levels (e.g., from diatom to C. trigangulifer) with potential biomagnifications. At the cellular and biochemical levels, after metals enter aquatic organisms they are re-distributed among different operationally-defined compartments inside the cells. This sub-cellular distribution determines the toxicity of metals in the aquatic organisms. Our results have shown that aquatic organisms may have different strategies to detoxify metals. For example, exposure routes differentially affect the antioxidant responses in a mayfly species exposed to cadmium. In addition, studies using in vivo rainbow trout vitellogenin assay have shown that a variety of media and chemicals ¾ including secondary and tertiary wastewater, groundwater, surface water from wetland and some herbicides ¾ showed estrogenicity. These results have provided new insights regarding the dynamic behavior of metals, molecular mechanisms affecting metal toxicity and detoxification, and the chronic effects of metals in aquatic organisms. In addition, these results could be helpful for water resource managers conducting risk assessments and for government agencies in decision making.