Phytoplankton Community Structure, Diversity, and Functional Groups in Urban River Under Different Black and Odorous Levels

Abstract

Phytoplankton community characteristics, diversity, and functional group analysis can respond to the environmental quality status of water bodies. To investigate the influence of urban river black odors on the phytoplankton community, from November 2020 to March 2021, 16 urban rivers in the Sichuan Basin were surveyed for water quality with 38 sampling points, and the degree of urban river black odor was evaluated based on the improved fuzzy mathematical model method and the k-mean principal color extraction method. The rivers were classified into four types:non-black and non-odorous, black and non-odorous, black and odorous, and black and odorous. The results showed that, with black and odorous water, the phytoplankton abundance increased from 1.329×105 cells·L-1 to 6.627×105 cells·L-1, and the dominant phytoplankton phylum decreased from Cyanophyta-Chlorophyta-Bacillariophyta to Cyanophyta. The phytoplankton biomass increased from 64.056 μg·L-1 to 120.465 μg·L-1, and the dominant phytoplankton phylum changed from Chlorophyta-Bacillariophyta type, adapted to a nutrient environment, to Pyrrophyta-Bacillariophyta-Cryptophyta type, adapted to an organic matter environment. The Shannon-Weaver diversity index decreased from 2.45 to 1.98, and Simpson's index decreased from 0.84 to 0.73. Twenty nine functional groups of phytoplankton were observed in the study area, and the growth strategy was reduced from S, R, C, CR, and CS to R with black and odorous water. In summary, phytoplankton indicators can better reflect the state of river black odor, and phytoplankton monitoring is a promising tool for urban river black odor management.