Monitorring Pyrethroids And Hg～(2+) In Water By Phototaxis Of Daphnia

The serious aquatic pollution limits the sustainable development of social economy in the world and water management is necessary for improve water environment. The mornitoring of water qualities, including physic/chemical and biological ones, is a fundamental procedure in water management. Practically, these methods need cooperate and replenish mutually to provide accurate. information in time. The biomonitor methods are now under developing and still have some limits such as poor comparasion and complex operation, It is thus urgent to set up sensitive, simple, accurate, quick and reliable biomonitoring methods for the application in the mornitoring of water environments.Daphnia (Cladocero: crustacea), an important animal of the diet for many fish, is widespread in the world and has a critical role in aquatic ecology chains. Daphnia is quite sensitive to deleterious substances in water. Therefore, they are used to indicate and forcast the safty of water environments.The phototaxis of Daphnia's is the character of light towards ang against migration, which is genectical controlled and also influenced by environemts. The utilization of phototaxis to mornitor the water quanlities is a new developing technique in the world. This new technique is under investigation and has less information in theories and practical application. So, much fundamental research work needs to be done, including the selection of Daphnia as biomonitor sensitive to toxicants but less to environment changes, the exploitation of relationship between the phototactic behavior of Daphnia and pollutants such as heavy metal, pesticide and their mixtures, and the comprehension of the effect of environmental conditions such as fish kairomones on the phototactic behavior of Daphnia.At present, the pollutions of heavy metals, pesticides and their mixtures are the main environmental problems in fresh water. But more researches were carried out on the pollution of single heavy metal and pesticide more than their mixtures. It is thus necessary to clarify the effects of heavy metals and pesticides on the phototactic behavior of Daphnia and to realize the biological and environmental effects in the condition of toxicant coexistence. They are important presuppositions that need to be solved before eliminating water pollution. In the present experiments, Daphnia carinata clone Dc₄, which was selected from Sanxia areas and breaded by self-copulation and Daphnia magna, were used as biomomitors to study the acute toxicity of Fenpropathrin, Alphaeypermethrin and Hg²⁺. The median lethal concentrations, phototactic indexes and interactions between pesticides and heavy metals were measured in the presence of single and mixtures of the toxicants with and without fish kairomones. The objectives are to provide theoretical and applicable means for the establishment of a quick, accurate and sensitive biomonitor method of pesticides and heavy metals in water. Following are the mian results obtained in the present experiments.The phototactic behavior of 4 Daphnia magna clones varied significantly inthe sequence: Dm₂＞Dm₄＞Dm₃＞Dm₁, indicating that Dm₂ was a good biomonitor for detecting toxicants in water.The phototaxis also varied greatly at the different ages even for same strain. It changed in rollowing sequence: 4d＞2d＞8d＞6d＞1d＞10d (Dc₄) and 4d＞2d＞6d＞8d＞10d＞1d(Dm₂). Dc₄ and Dm₂ were thus adopted at the age of 4d in the present experiments.On the base of the acute toxicity of single toxicant to Dc₄, equivalent amount of fenpropathrin, alphaeypermethrin and Hg²⁺ were mixed with any two or three, indicating antagonistic action of the mixtures.There were significant correlation between the Dc₄ phototaticindex (Ip) and the concentrations of fenpropathrin (y=72.9x2-16.6x+0.11, R²=0.876), between Ip and alphaeypermethrin (y=159.2x2-23x+0.076, R²=0.83), and between and Hg2+ (y=0.38-25.2x, R²=0.97, p＜0.01).The changes in phototactic indexes of Dc₄ and Dm₂ were different in the presence of single toxicant from those in the mixtures of pesticides and heavy metals. There wereno interaction effects of these toxicants on phototactic behavior. This is to say that the toxicity changed little, if any, in the separate or mixed.The fish karimone in water could significantly decrease the phototactic index of Dc₄ and Dm₂.The phototactic behavior of Dc₄ and Dm₂ in response to toxicants in water with fish karimones free were different from that with fish karimones. The t-test indicated that fish karimones influenced significantly on the toxicity of Alphaeypermethrin.