Microalgae were investigated in two constructed Sonneratia apetala wetlands in the 14th and 19th waterchannels of the Nansha district

Guangzhou city

China. Based on the data collected at 8 sampling points in spring and autumn in 2009

the species composition

abundance

community structure and diversity indices of microalgae were estimated to evaluate the wetland water quality and purification capacity of 

S. apetala.

 The microalgae were extremely abundant

with 338 species and the abundance ranged from 10

5

～10

7

ind/L The highest algal abundance occurred in the 19th channel

indicating a hyper-eutrophic status. Organic pollution was common in the study area

yet water quality in the 14th channel was better than that in the 19th channel due to its good hydrological conditions. Isolation of water in the 

S. apetala

 wetlands can lead to heavy eutrophication

so water circulation must be considered in the management of constructed mangrove wetlands.