Ecological Mechanism Of Heavy Metal Accumulation In Urban Wild Animals

As a result of the global industrial revolution and urbanization,contamination of the ecosystem by heavy metals has given rise to one of the most important ecological and organismic problems,particularly wildlife.The bioaccumulation of heavy metals in urban wild animals can be influenced by several factors,including foraging behaviour,habitats preference and microhabitats.The transfer of pollutants from chemical fertilizers through food webs within cropland is well documented;however,its impacts on the wild animals that forage on croplands but roost in other locations remain poorly understood.The potential for this cross-ecosystem ‘spillover' of pollutants is greatest for bats,some of which exploit urban settlements as roosting niches but must travel long distances to reach croplands as foraging niches.Here,we used hairs from a colony of insectivorous bats,Chinese Noctule(Nyctalus plancyi),from an urban area in Southwest China to assess whether exposure to heavy metals metalloids by the bats varied from 1975 to 2016.Historical changes occurred in hair cadmium(Cd)concentrations in adult females,which was exclusively explained by the regional fertilizer application intensity(FAI),even considering the potential impacts of Cd emissions in urban areas,as indicated by camphor trees(Cinnamomum camphora)near the bats' roosting niche,and the potential impacts of Cd in industrial wastewater,as documented in authorized databases.Therefore,the data from this bat colony,as urban dwellers,indicates Cd accumulation and cross-ecosystem transfer from rural croplands to an urban area.Ants due to their nesting habits are ideal for studying temporal fluctuations in trace metal accumulation,changes in morphological traits,as well as for assessing evolutionary processes and monitoring environmental impact of metals derived from human activities.Different ants(Pheidole nodus,Nylanderia bourbonica,Camponotus japonicus and Tetramorium tsushimae)and habitat variables surveyed from the urban garden were processed by means of LC-AFS evaluate the levels and the potential bioaccumulation of mercury.One-way analysis of variance(ANOVA)was applied to show the differences in mercury in ant species.Three species of ant(Pheidole nodus,Nylanderia bourbonica,Camponotus japonicus)had significantly higher mercury enrichment than the Tetramorium tsushimae.Result from the redundancy analysis showed that three species of ants(Pheidole nodus,Nylanderia bourbonica,Camponotus japonicus)were more abundant in the habitats with complex vegetation types.Ant habitat preference played a dominant role in determining species Hg enrichment.Next,The Hg concentration in the Pheidole nodus populations,varied over the course of different site in response to microhabitat type.Using generalized linear models,we found that herb diversity and soil physical and chemical properties(P,Cation Exchange Capacity and Clay ratio)concentrations significantly affected Hg concentration in ant populations.These results indicate that microhabitat in terms of herb type and soil maybe is the positive factor influencing ant mercury enrichment.