How Submerged Macrophyte Restoration Promotes a Shift of Phytoplankton Community in a Shallow Subtropical Lake

Abstract

Submerged macrophyte restoration has been widely used to decrease phytoplankton and combat eutrophication in many temperate shallow lakes. However, very limited studies have been done to explore its potential in decreasing phytoplankton in subtropical shallow lakes. We hypothesize that macrophyte restoration can also decrease phytoplankton and shift community structures in subtropical shallow lakes. In order to test our hypothesis, we consistently investigated submerged macrophytes, nutrients, and phytoplankton for three years in a shallow subtropical lake. Multiple analytical methods were employed to assess the effect of macrophyte restoration on the phytoplankton community. The results showed that the density and biomass of total phytoplankton after restoration were less compared to those before the restoration. During the restoration, species diversity significantly increased every year, but the change in species richness was not significant. Moreover, phytoplankton community structure also transformed greatly. Especially cyanobacteria density gradually decreased until almost disappeared; Chlorophyta density also significantly decreased from 4.6 × 10 6 cell/L to 1.9 × 10 6 cell/L. Although changes in the densities of other groups were not significant, their ratios in total phytoplankton significantly increased. The changes in four dominant species were also significant during the restoration, with Microcystis aeruginosa, M. incerta, and Chlamydomonas sp. significantly decreasing, but Chlorella pyrenoidosa significantly increasing. Correlation analysis between phytoplankton and environmental factors (macrophyte and water quality) showed that macrophytes were negatively correlated with total phytoplankton, TN, and COD, but total phytoplankton was positively correlated with TN and COD. These relations indicated that macrophyte restoration might not only directly inhibit phytoplankton growth, but also indirectly decrease phytoplankton by both bottom-up and top-down controls of phytoplankton. Therefore, these results basically proved our hypothesis, and more attention should be focused on this method in future lake management.

Exploring the Spatial-Seasonal Dynamics of Water Quality, Submerged Aquatic Plants and Their Influencing Factors in Different Areas of a Lake

“…The composition of submerged aquatic plants integrates the chemical, biological and spatiotemporal characteristics of their surrounding environments, which could reflect the nutrient supplies of freshwater ecosystems affected by anthropogenic impacts [12,48]. Previous studies demonstrated that nitrogen and phosphorus had significantly adverse effects on the growth of submerged aquatic plants, and the effects of N were even more significant when TP concentration was not high [49,50]. Our results suggested that the submerged aquatic plant biomass was negatively influenced by the concentrations of NH 4 + -N and TN in dry and wet seasons.…”

Microzooplankton Grazing and Phytoplankton Growth in a Chinese Lake

“…Submerged macrophytes are important and crucial for stabilizing the clear water state in eutrophic lakes [34]. As one of the important measures in the eutrophic water ecological restoration project, submerged vegetation reconstruction was effective [35][36][37]. The implementation of this technique had an important influence on the nutrients and plankton community structure in fresh water [38][39].…”

The Relationship of Water Quality to Epipelic Diatom Assemblages in Cebong Lake, Dieng Indonesia

“…Bioindicators are utilized to evaluate human effects on the environment. In terms of an aquatic ecosystem, particularly in lake ecosystem, the organism or groups of organisms that are usually used as a bioindicator of water quality are phytoplankton [8][9][10][11], microbes [12][13], invertebrates [14][15][16], diatoms [17][18][19][20][21][22][23][24][25][26][27][28], macrophytes [29][30], and fish [31].…”