Metazooplankton community structure and its relationship with environmental factors in the middle and lower reaches of Hanjiang River
Four investigations on the community structure and water environment characteristics of metazooplankton were carried out at seven points such as Danjiangkou,the main stream of the middle and lower reaches of the Hanjiang River.The relationship between metazooplankton community and environmental factors was studied by using statistical analysis methods such as principal component analysis,Spearman correlation analysis and redundancy analysis.The results showed that 51 species of metazooplankton were detected in the middle and lower reaches of the Hanjiang River,including 16 species of cladocerans,16 species of copepods and 19 species of rotifers.The highest abundance in Hanchuan section of the main stream of Hanjiang River was 1500.1 ind.·L-1,and the lowest abundance in Danjiangkou was 31.3 ind.·L-1;The highest biomass in Hanchuan section of Hanjiang River was 1.80 mg·L-1(July 2018),and the lowest biomass in Danjiangkou was 0.05 mg·L-1(November 2017).The abundance and biomass of metazooplankton in the middle and lower reaches of Hanjiang River increased along the flow direction.Compared with the previous monitoring data,the abundance and biomass of metazooplankton increased sharply and the species decreased.The results of PCA analysis showed that environmental factors such as nitrogen and phosphorus had an obvious impact on the station in January 2018,and the temperature had a positive correlation with the station in July;Redundancy analysis showed that the impact of environmental factors on metazooplankton community was not obvious.Considering that the change of metazooplankton community was not only affected by water pollution along the river,but also affected by other factors not investigated.