Plankton communities along a subtropical urban river (Houxi River, southeast China) as revealed by morphological and molecular methods

Abstract

Few studies of plankton communities address anthropogenic influences on lotic ecosystems using multiple methods. Here we used both morphological and molecular techniques (denaturing gradient gel electrophoresis) to explore the spatial diversity of the plankton communities in a subtropical urban river during the month of March 2011. We identified 64 morphological taxa and 36 molecular taxa. Our results indicated that plankton communities in the Houxi River might be strongly impacted by anthropogenic disturbance. Nutrient concentrations (nitrogen and phosphorus), water temperature, conductivity, and suspended solids increased whereas dissolved oxygen decreased dramatically from upstream to downstream, and these environmental variables were found to be significantly related (p < 0.05) to the plankton community composition. The genera tolerant to organic pollution, such as Cyclotella, Fragilaria and Navicula (Bacillariophyta), and Ankistrodesmus and Scenedesmus (Chlorophyta), were dominant in the river. The comparative (Mantel-type) tests on similarity matrices (RELATE) analysis revealed that the denaturing gradient gel electrophoresis (DGGE) profile was closely related to species composition. In addition, the matching coefficient was higher between the DGGE profile and environmental variables than between species composition and environmental variables. Our results suggested that DGGE fingerprinting was more effective for examining the relationship between the plankton communities and environmental conditions than the morphological method, and they further provided new molecular insight into the community-level assessment of water quality and lotic ecosystem health.