Seasonal heterogeneity of nekton community and its ecological effect at Daya Bay mouth

We analyzed the resource dynamic, diversity and community structure of nekton based on the data collected by demersal trawl at Daya Bay mouth in 2015. The results show that the density of nekton in summer was significantly higher than that in the other seasons (F=4.556, P=0.01), and it was mainly affected by the seasonal alternation of nekton dominants. The first dominant species in each season were Paerargyrops edita (in spring), Thamnaconus hypargyreus (in summer), Leiognathus brevirostris (in autumn) and Portunus gladiator (in winter). The Shannon-Wiener diversity index of nekton community varied between 2.35 and 2.66, and the seasonal difference was insignificant (F=0.597, P=0.623). However, the cluster and non-measured multi-dimensional scale sequencing (NMDS) analyses show that the dissimilarity of nekton community in different seasons varied from 69.13% to 80.77%. Therefore, the single α diversity index can not reflect the characteristics of the nekton community of the survey area effectively. The results of redundancy analysis (RDA) indicate that there is a clear relationship between seasonal heterogeneity of nekton community and environmental factors such as water temperature, dissolved oxygen, salinity, transparency, pH and chlorophyll a.