No abstract

In this study, the concept of functional traits was used to classify zooplankton into functional groups and their seasonal dynamics were determined in relation to physico-chemical factors in a highly turbid and nutrient-rich wetland. This study revealed a seasonal variation of both physico-chemical factors and biomass of zooplankton functional groups. Water temperature (TEP), total phosphorus (TP), ferrous ion (Fe 2þ) and total carbon (TC) were significantly higher in summer while water transparency (SD) was notably higher in spring. Zooplankton functional group biomass was higher in summer (5.11 mg/L) followed by winter, autumn and spring (0.91, 0.72 and 0.28 mg/L, respectively). Large copepods and cladoceran carnivore (LCC) was the dominant functional group in spring accounting for about 86.7% of the total biomass. In summer, MCF (Middle copepods and cladocerans filter feeders) was the dominant group probably because of the optimal temperature and availability of nutrients. Pearson correlation and RDA analysis results suggested that Fe 2þ , TP and TEP were the major factors influencing zooplankton functional groups. Notably, turbidity was not the main factor despite the fact that Small Xingkai Wetland Lake is a very turbid lake. The variation of zooplankton functional groups among seasons highlights the role of physicochemical factors in structuring zooplankton composition.

In this study, the concept of functional feeding groups was used to classify and model the seasonal variation of zooplankton functional groups in relation to environmental variables. A total of 48 zooplankton species were observed in the reservoir and grouped into 8 functional groups. Both environmental variable and the biomass of zooplankton functional groups vary spatially and seasonally. Water temperature, water transparency, total nitrogen and nitrates were significantly higher in summer, while chlorophyll-a and ammonium were higher in autumn and spring, respectively. Biomass of zooplankton was significantly higher in summer (245.81 μg/L), followed by autumn (196.54 μg/L) and spring (54.25 μg/L). Group RF (rotifer filter feeders) dominated in spring, accounting for 80% of the total biomass. In summer and autumn, group RC (rotifer carnivore) and SCF (small copepods and cladocerans filter feeders) were the dominant, respectively. Total nitrogen, total phosphorus, ammonium, chlorophyll-a and water transparency were the major factor influencing zooplankton community. Group RF was positively influenced by ammonium and total phosphorus, while RC, SCF and MCF (middle copepods and cladocerans filter feeders) were positively correlated with chlorophyll-a. Top-down control of phytoplankton by groups RC, SCF and MCF in Xiquanyan reservoir is not strong enough to produce negative effect. Increase in predator size biomass did not strengthen top-down control on prey. It is quite clear that the zooplankton function groups of Xiquanyan reservoir followed a predictable seasonal pattern. This therefore highlights the significance of environmental variables in structuring plankton composition in the reservoir.

In this study, the concept of phytoplankton functional groups was used to assess phytoplankton community structure in an attempt to better understand their spatial and seasonal variation in extremely alkaline Dali Nur Lake. Samples were collected for analysis during spring, summer and autumn for a period of two years. We identified 13 phytoplankton functional groups (Lo, S1, H1, P, C, MP, X3, Y, X2, W1, J, F, and T) among 37 species out of which 7 groups Lo, H1, P, C, MP, X2, and F were dominant. The biomass of phytoplankton functional groups in the Lake exhibited a strong seasonal variation with the highest biomass value observed in autumn and lowest in spring. Functional groups MP, P, and C were dominant in spring when the temperatures were very low. Groups H1 and X2 were the dominant in summer corresponding to higher temperatures. In autumn groups Lo and X2 were the dominant corresponding to high levels of total phosphorus (TP). Our study revealed that alkalinity, pH, arsenic, chemical oxygen demand, and TP are the most important physical-chemical variables structuring the phytoplankton functional groups in Dali Nur Lake. Functional groups Lo and X2 were mainly influenced by TP while groups MP and P flourished better under high conditions of arsenic. This study reveals the importance of physical-chemical variables in the spatial and seasonal gradient, in structuring phytoplankton functional groups, and consequently in the assessment of environmental status of the lake.