The Characteristics Of Zoobenthos Community And Their Relationships To Environment Factors In Mainstem Of Ganjiang River

The ecological study of zoobenthos was conducted on ten typical sampling sections selected in the main stream of the Ganjiang River.In January,April and July of 2019,the combination of qualitative and quantitative methods was used to investigate and sample the benthos in the mainstream of the Ganjiang River.The multi-statistical method was used to analyze the distribution characteristics of zoobenthos community structure.The B-IBI index evaluation system was established to evaluate the health of the mainstream water ecosystem of the Ganjiang River.The main environmental factors affecting zoobenthos were identified by the canonical correspondence method.The correlation between the two has accumulated a data base for the environmental protection and ecological restoration of the mainstream of the Ganjiang River and provided a reference basis.A total of 24 species of zoobenthos were detected during the survey,of which mollusks were the main group,with 11 species,accounting for 45.8%;aquatic insects were next,with 6 species,accounting for 25%;and 4 oligochaetes,accounting for 16.7%.;There are only 3 other groups,accounting for 12.5%.The annual average biological density and average biomass were 49ind./m~2 and 46.82g/m~2,respectively.The zoobenthos community in the main stream of the Ganjiang River has a certain spatial and temporal distribution characteristics.The change of species in different water regimes is the dry season of January>the wet season of April>the flood of July,and the change in different river sections is upstream>midstream>downstream.During the survey period,the range of the Shannon Weiner Index in the Ganjiang River Current Diversity Index was between 0 and 1.741 for the whole year.The average change for different water periods was the dry season>the wet season>the flood period;the richness index was all The range of the year is 0?1.884,the highest value point appears in the dry season of January,and the lowest value point appears in each water period;the uniformity index ranges from 0.323 to 0.975 in the whole year,and the highest value point and the lowest value point appear in April flood season.Cluster analysis showed that 12typical sections of the mainstream of the Ganjiang River can be divided into 4 groups,with high similarity within the group and large differences between groups.The differences between the sections are related to the hydrological conditions and aquatic organisms in the mainstream of the Ganjiang River.The evaluation results of the B-IBI index system show that the health status of the mainstream of the Ganjiang River is generally in a general state,and the spatial difference is large.The sections in the healthy or sub-health state are GJ2#,GJ3#,GJ4#,GJ6#and GJ11#,accounting for 41.7%;the general state of the section is GJ5#,accounting for 8.3%;The health status of the six sections GJ1#,GJ7#,GJ8#,GJ9#,GJ10#(Waizhou)and GJ12#They are all in a very poor state,accounting for 50%.The application of canonical correspondence analysis shows that nutrient salt,The water environmental factors affecting the community structure of zoobenthos in the mainstream of the Ganjiang River in different periods are significantly different.conductivity,and dissolved oxygen are the main influences on the community structure of zoobenthos in the mainstream of the Ganjiang River.factor.