Biotoxicity Assessment For Water And Deposit Sediments In Longhong Ravine And Beili Lake Of West Lake In Hangzhou, China

With the rapid development of industrialization and urbanization in China, many landscape lakes have been polluted to different extent. Eco-toxicity and environmental safety of landscape water are attracting more and more attentions. West Lake in Hangzhou is a world-famous sightseeing place, and the representative of landscape lakes. Longhong Ravine locates in the southeast of West Lake and is one of the main water sources of West Lake. Beili Lake is the westeast part of West Lake. In this study, Longhong Ravine and Beili Lake were investigated as the representative area of West Lake. We set 10 and 5 sampling sites along Longhong Ravine and Beili Lake, respectively. Water and deposit sediments were sampled for four times during May 2014 to Dec.2014. Physicochemical indexes of the water were analyzed in different seasons. Biological toxicity was assayed in use of luminescent bacteria, Xenopus Tropicalis embryos and Caenorhabditis elegans. The aim of this study is to fully check water quality and ecological safety of West Lake. Additionally, transgenic C. elegans CL2166 was creatively utilized to detect toxicity of multiple environment samples including from West Lake. The main results are in the followings: (1) For Longhong Ravine and Beili Lake, the monthly mean of water temperature was 24.16±6.12℃, pH was 8.10±0.87, DO was 9.03±1.76 mg/L, NH4+-N was 0.25±0.24mg/L, NO3--N was 4.09±2.68 mg/L, TN was 4.83±2.66 mg/L, TP was 0.05±0.02 mg/L, CODMn was 3.95±1.09 mg/L. The seasonal changes of pH and DO were consistent. The index of NH4+-N meets Class II water standard of the surface water. TP and CODMn, perfectly meet with Class III surface water standard. However, the value of TN is further high than Class V water, which is mainly because of the high value of NO3--N.(2) Luminescent bacteria were used to assay the comprehensive toxicity of the water and sediments in Longhong Ravine and Beili Lake. Results showed that over 80% samples induced promotion of luminescent intensity of Luminescent bacteria, and this effect was much more obvious in winter than that in summer. The positive effects were related to DO value of water. However, obvious inhibitory effects of luminescent intensity were only observed in a few months at L4, L6, L7, L10 sites. It indicates that water from West Lake is generally nontoxic to luminous bacteria, and nutritive for growth of the luminous bacteria.(3) Results of FETEX showed that the water and deposits from Longhong Ravine and Beili Lake did not affect the hatching rate and survival rate of Xenopus Tropicalis embryos. As for body length,96% samples showed no observable effects or positive effects, only 4% samples resulted in obvious inhibitions. Of all the samples (120), only three (L4, B1 and B4 sampling site) induced teratogenic effects. The main malformation phenotypes include abdominal edema, enlarged trunk and enlarged proctodaeum, which were all slightly abnormal.(4) Water and sediments of Longhong Ravine and Beili Lake did not show acute lethality to the wild N2 C. elegans (for 48h exposure). Only two samples showed obvious lethal effects (L5 in Aug.2014 and Dec.2014). Furthermore, GFP marked transgenic nematode CL2166 was utilized to assay for water samples from Longhong Ravine and Beili Lake. These water samples did not lead to any changes of glutathione S-transferase expression in C. elegans.(5) Sub-lethal exposure to both phenol and chromium chloride could induce the increase of gst-4::GFP expression of transgenic nematode CL2166 in a dose-depend manner. The toxicity of the polluted soil samples from a Galvanization Company was successfully detected out by this transgenic strain of C. elegans, which was consistent with that from the luminous bacteria. These results indicate that the expression level of gst-4::GFP can reflex oxidative damage toxicity induced by the environmental samples.In summary, water quality of Longhong Ravine and Benli Lake is extensively good. Nevertheless, high level of TN and NO3--N values needs to be considered. Management of nitrogen sources should be strengthened including tea garden, catering and village sewage, in order to prevent water eutrophication. Biological toxicity assays showed that the water and deposits of Longhong Ravine and Beili Lake had low ecological risks. However, a few samples showed lethal and teratogenetic toxicity, which was related to local pollution such as the use of pesticides. For the first time, Caenorhabditis elegans was used to detect the toxicity of environmental samples in the present study. We also revealed that the transgenic nematodes CL2166 could assay for the environmental stress, which had significant application in toxicity detection for environmental samples.