Spatiotemporal Distribution Characteristics of Phytoplankton in Sizaopu River, Ningbo Qianwan New Area

Tianjin University of Science and Technology, College of Marine and Environmental Sciences, 300457 Tianjin, China

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Abstract

From April to September 2025, monthly sampling was conducted in both the treated and natural sections of the Sizaopu River, Ningbo Qianwan New Area, to characterize the spatiotemporal dynamics of phytoplankton communities. In the treated section, a total of 104 species belonging to 64 genera and 6 phyla were identified, with an average density of 1.27^108 cells L^-1. Ten dominant species were recorded; notably, the dominance pattern was most simplified in August, when only Pseudanabaena limnetica prevailed. The average values of the Shannon-Wiener diversity index (H') and Pielou's evenness index (J) were 0.96 and 0.28, respectively. In the natural section, 111 species from 66 genera and 6 phyla were observed, with an average density of 1.79 x 108 cells L^-1. Seven dominant species were found, with the fewest in June, when Microcystis aeruginosa was the sole dominant. The average H' and J' in this section were 0.84 and 0.26, respectively. Overall, the phytoplankton community structure was similar between the two sections, with Cyanophyta being the most dominant phylum in both. However, the treated section exhibited a more stable community.