Influence Of Water Environment Remediation For Urban River On Mosquito Breeding Based On Simulation Test And Field Study

With the development of urbanization and socio-economic,the river water pollution status was not optimistic in China.Control and remediation of polluted urban rivers have been applied widely.Variations of urban river water environment would inevitably change the habitats of mosquito,and then,affected the community structure,population density and temporal-spatial distribution of mosquitoes,which would further intensify the risk of mosquito-borne diseases for banks of urban rivers.With the support of National Natural Science Fund project "Relationship and harmony assessment of urban river water environment remediation and mosquito reproduction "(51278192),relationship and mechanism of mosquito breeding and different water environmental backgrounds and remediations in urban rivers were explored through background investigation,simulation test and field study,in order to provide a scientific basis for the coordinated development of water environment remediation and mosquito control.This dissertation focused on the following four aspects:(1)simulating the influence of different water pollution levels on growth and development of Culex pipiens pallens and Aedes albopictus;(2)investigating influence of different plants,zooplanktons and mosquitofish on growth and development of mosquito larvae;(3)investigating effects of different plants and artificial aeration on oviposition behavior of Culex pipiens pallens.Volatile components of plants were analyzed by Solid phase microextraction-Gas chromatography-Mass spectrometry(SPME-GC-MS)in the hope of finding coupling relation between plants and oviposition selectivity of adults;(4)water samples and mosquitoes from ten rivers(segments)of Shanghai city and Wenzhou city were surveyed in field,in order to better understanding the key environmental factors influencing mosquito breeding of urban rivers,and promote the coordinated development of river remediation and mosquito control.The main findings were as follows:(1)There was greater influence on hatching rate,pupation rate and body weight than eclosion rate of Aedes albopictus and Culex pipiens pallens in different water pollution levels.Comparison of Culex pipiens pallens,Aedes albopictus was typically inclined to cleaner water.Under the simulation test,developmental rate of Culex pipiens pallens was found faster than Aedes albopictus,and body weight of former was greater than the latter.(2)The hatching rate of Culex pipiens pallens increased 3%?30.5%due to the presence of aquatic plants.There was a significant influence on larval stage by the five plants.Predation efficiency of mosquito larvae by Cladocera and mosquitofish was related to the larval ages and quantity ratios.The mortality of first instar larvae increased from 13.33%to 100%when the ratios of Cladocera and larvae rose from 10:10 to 200:10.Half lethal time and lethal time of a 0.8 cm mosquitofish against 10 first instar larvae was 1.08 h and 3.38 h respectively,and 3.35 h and 5.00 h for a 3 cm mosquitofish.Mosquitofish was typically inclined to pray on the smaller size of early instar larvae and zooplanktons,and then prayed on the bigger size of late instar larvae.There was not significant for mosquitofish to choose between cladocerans and copepods.Aproximately 3.78±0.72 larvae of Culex pipiens pallens would be predated by a 3 cm mosquitofish in an hour.An effective predating rate was obtained on a 1 m2 ponding stocking with 32 individuals of 3 cm mosquitofish for 120 first instar larvae of Culex pipiens pallens in an hour.(3)Artificial aeration and excessive density of aquatic plants would hinder oviposition of Culex pipiens pallens effectively,and repellent effect of mosquito by continuous aeration was better than intermittent operation.The value of oviposition activity index for Culex pipiens pallens were ordered as follows:Acorus tatarinowii(0.58)>Myriophyllum aquaticum(Vell.)Verdc.(-0.16)>Houttuynia cordata Thunb(-0.64)>Hydrocotyle vulgaris(-0.70)>Mentha spicata(-1.00).Results indicated that Acorus tatarinowii was an attractant for oviposition of Culex pipiens pallens,and a remarkable repellent effect on oviposition of Culex pipiens pallens was found in plants of Mentha spicata,followed by Houttuynia cordata Thunb and Hydrocotyle vulgaris,and Myriophyllum aquaticum(Vell.)Verdc.has the weakest repellent effect.Benzene from volatile components of plants showed potential attractant for oviposition of Culex pipiens pallens,while terpenes especially monoterpenes were regarded as the main components of repellent effects.(4)Urban river water was considered as one of potential habitats for some mosquito species.Four of ten rivers were presented as positive rivers.It was difficult for mosquito to breed in the river when its water quality was better than class IV of surface water standard.High incidence of mosquito larvae was noted in late spring-early summer,and low incidence was observed in winter of river SX and river JS.River SX and JS showed two peaks of larvae abundance in April-June and October-December,respectively.Nevertheless,only one peak appeared for river GY and TPH in May-June.Physico-chemical parameters of river water might have a certain influence on immature mosquito breeding.Organic carbons,nitrogens and phosphorus of river water were the important nutrition sources for mosquito larvae potentially.Both of terrestrial plants alongside river and aquatic plants in river affected mosquito breeding.Aquatic plants applied in rivers resulted in favor of mosquito breeding.Larval density from rivers increased with the rise of shading rate of river water surface.(5)The mosquito species identified from study rivers were namely Culex pipiens pallens,Culex quinquefasciatus,Culex fuscanus,Culex vagans and Aedes albopictus respectively.Of which,Culex pipiens pallens was the predominant species.The appearance of Aedes albopictus in polluted river SX might be related to the container-trash floating on river surface.Appearance of Culex fuscanus in river SX of Wenzhou city was reported for the first time.Remediation of river would influence mosquito breeding significantly,larval density of river GY after measures of sewage interception,dredging,hardening revetment and river surface cleaning was obviously fewer than before.Measures such as sewage interception,river dredging,fish stocking,artificial aeration,hardening revetment,river surface cleaning,reducing shading area,applying mosquito repellent plants could decrease the mosquito abundance from rivers effectively for control and remediation of urban polluted rivers in the future.