Understanding the Ecological Response of Planktic and Benthic Epipelic Algae to Environmental Factors in an Urban Rivers System

Liling Xia,Yuelong Zhu,Zhenhua Zhao

doi:10.3390/w12051311

Abstract

Many studies have been concentrated on the distribution of algae in lakes, rivers, and seas, however, few studies have been concerned about their distribution and relation with polluted urban rivers. In this study, the spatio-temporal variation characteristics of water quality and algae community in Nanjing city were investigated with microscopic examination for one year. Results showed that the water pollution in this area was mainly related to high concentration of nitrogen (NH3-N and TN (Total nitrogen). There was a total of 77 species of algae in the studied rivers from June 2016 to May 2017, among which 73 species of planktic algae and 34 species of epipelic algae, in which the abundance and biomass of the latter were 1925 and 904 times that of the former, respectively. The two kinds of algae had different change tendencies which were related to seasons. For planktic algae, the abundance and biomass decreased in this season sequence: summer, spring, autumn, and winter. For epipelic algae, the abundance and biomass were relatively higher in winter. The dominant community of planktic algae was Chlorophyta-Bacillariophyceae-Cyanobacteria type, while that of epipelic algae was Bacillariophyceae—Cyanobacteria type. Most of the present algae were bi-trophic species, and were tightly related to the pollution characteristics of the rivers. The key environmental factors for planktic algae are T, TN, and TP, and those for Epipelic algae are N:P and TN. The relation between the community composition of planktic and epipelic algae and environmental parameters are highly complex, and it is worth carrying out further study to clarify their interaction mechanism.

Highlights

Algae are the primary producer of aquatic ecosystem, and play a key role in material cycling and energy transformation processes [1]
The aim of this study is to explore the relations between the pollution characteristics of heavily polluted urban rivers and the ecological response of planktic and epipelic algae on environmental factors, and to identify the key environmental impact factors influencing the distribution and composition of planktic and epipelic algae in a typical urban rivers system
The measured results of water quality of the studied rivers are shown in Figure 2 and it indicates that the dissolved oxygen (DO) level was obviously higher in spring and summer than in autumn and winter

Summary

Introduction

Algae are the primary producer of aquatic ecosystem, and play a key role in material cycling and energy transformation processes [1]. The planktic algae can transform inorganic materials into organic materials via solar energy, and the produced organics are stored by consumers, which ensured the existence and propagation of algal community [2]. After the death of algae, the residue is degraded by microorganisms, the produced organic debris either settle to the bottom of a water body or are suspended in a water layer. These micro-particles can again be absorbed to the surface of algae and affect their photosynthesis process. When the propagation ability of algae exceeds the degradation ability of heterotrophic bacteria, a great amount of organics will remain in the water body, which is the fundamental reason for water quality degradation of urban rivers [3]

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Conclusion