The Influence Of Anthropogenic Disturbance On Benthic Community Diversity And Effect Analysis

Biodiversity is characterized as alpha,beta and gamma diversity in terms of spatial scales.Alpha diversity focuses on the number of species under local uniform habitat,beta diversity refers to the differences of species composition along the environmental gradient in different habitat or the turnover rate of species along the environmental gradient,and gamma diversity describe the diversity of regional or continental scale and refers to the number of species.The effect of environmental gradient on biodiversity could be more elucidated in terms of alpha,beta and gamma diversity index at multiple spatial scales.Anthropogenic activity is key factor resulted in the biodiversity decrease.Macroinvertebrate and benthic diatom are indicators of stream water quality and play an important role in maintaining stream ecosystem function.It was demonstrated that alpha diversity decreased with the latitude increase and anthropogenic activity decline the beta diversity.However,is such conclusion a general one or specific one still not very clear.We focused on the two questions in this study.1)Is the alpha diversity of macroinvertebrate and benthic diatom showed the pattern as expected decreasing with latitude increase?2)Do macroinvertebrate and benthic diatom diversity show similar response to anthropogenic disturbance paticular the decline of beta diversity?We collected maroinvertebrate,benthic diatom and environmental variables at Irtysh river basin in Altay,Wei river basin in Xian(30 sites),Qiantang river basin in Hangzhou(30 sites),Li river basin in Guilin(36 sites)and Lantsang river basin in Xishuangbanba(40 sites).Then we calculated alpha,beta and gamma diversity.We used linear regression analysis to explore the relationship between the alpha diversity and latitude,nonparametric test and PERMDISP to compare the difference of alpha and beta diversity between least disturbed condition and disturbed condition,and NMDS for community species composition among samples.Db-RDA analysis results show that for the ER and WH watershed,the explanation environmental factors on its amount of beta diversity are similar between least disturbed sites and disturbed sites,while the other three river basin environmental factors of macroinvertebrates beta diversity interpretation volume decreases obviously.Authors suggest that it may be due to different types of interference which caused to beta diversity mechanism may vary.Relative to the farmland and pasture interference,the benthic animal community of urbanization significantly lower beta diversity is more likely due to the level of urbanization and the factors of history development.We found,in terms of macroinvertebrate alpha diversity,the relationship between latitude and abundance,species richness and Sipmpson index demonstated the expected pattern,however the Shannon evenness index demonstrated the significantly opposite pattern as expected.Neverthess,in terms of benthic diatom,all of the alpha diversity demonstrated non-significant pattern that decrease with latitude increase.In addition,anthropogenic activity significantly influenced the macroinvertebrate alpha diversity.However,in terms of benthic diatom,except the abundance and richness in QTJ showed significant difference between least disturbed and disturbed sites,no significant difference were found between least and disturbed sites in other four watersheds.We found obvious difference of the macroinvertebrate species composition between least disturbed and disturbed sites,however we found no obviously difference of benthic diatom species composition.In terms of beta diversity,macroinvertebrate,beta diversity of least disturbed sites was significantly higher than those of disturbed sites in all five regions when using absence-presence data.However,when we calculated beta diversity using abundance data,beta diversity of disturbed sites was significantly higher than those of least disturbed sites in WH and LCJ.For benthic diatom,we found no significantly different between least disturbed sites and disturbed sites no matter using Bray-Curtis index or Jaccard's index.In a summary,we found that macroinvertebrate alpha diversity will significantly decrease with the latitude increase,benthic diatom alpha diversity also showed this kind of trend..The responses of macroinvertebrates and benthic diatoms were different.Both alpha and beta diversity of macroinvertebrate significantly decreased in disturbed sites,in contrast,both alpha diversity and beta diversity of benthic diatom showed nosignificant difference between least disturbed and disturbed sites.Our results implied that macroinvertebrate showed more resposible to human disturbance than benthic diatom when using snapshot samples,accordingly more potential indicators in water quality bioassessement in China.