Comparisons of Zooplankton Community Structure between with- and without- Pesticide Applications on Rice Fields

Nattaporn Plangklang,Sujeephon Athibai

doi:10.3390/d13120644

Abstract

Herbicide usage in rice fields over time may have a direct and indirect influence on the biodiversity of the fields. The impacts of herbicide usage on non-target organisms were assessed by examining the species richness and zooplankton density of two rice fields. One was 2.08 hectares in size and had been treated with pesticides during the sampling year (RF-PA). The second field, measuring 1.76 hectares, had received no pesticide treatment (RF-NPA). Every two weeks, zooplankton was quantitatively collected from ten sampling sites in each field. At each station, 20 L of measured water was filtered through a plankton net with a mesh size of 20 µm and preserved in 1% Lugol’s solution. The results revealed that RF-NPA and RF-PA had 112 and 88 species of zooplankton, respectively, with an abundance-based Jaccard index (Jabd) of 0.438. The total zooplankton density in RF-NPA was 24.4 ind./L, significantly higher than the 16.6 ind./L in RF-PA (p < 0.001). The Shannon-Wiener diversity index (H’) and evenness (J) were highest in RF-NPA at the second sampling (3.45 and 0.75, respectively). These results indicate that glyphosate application affects the diversity of species and density of zooplankton in rice fields.

Highlights

Insect infestation, weed competition, and fungal and bacterial pathogens are serious problems that lead to reduced rice production [1]
In RF-NPA, the first sampling revealed a higher value of water temperature, electrical conductivity (EC), and total dissolved solids (TDS) than the second sampling; on the other hand, Dissolved oxygen (DO), nitrate content, and chlorophyll a content had significantly lower values in the first sampling than in the second sampling (p < 0.05) (Figure 2)
The findings provided a realistic picture of the effects of herbicide usage on zooplankton assemblages and environmental variables under field conditions

Summary

Introduction

Insect infestation, weed competition, and fungal and bacterial pathogens are serious problems that lead to reduced rice production [1]. These problems are often solved by applying a wide range of pesticides to protect rice crops [2]. The quantity of pesticides used conforms to the number of pesticides imported into Thailand. Herbicides, insecticides, and fungicides are the main three pesticide imports [3]. It is a common practice to drain rice-field water into irrigation canals. The contaminated water from rice fields can directly and indirectly affect small organisms as well as zooplankton [6]

Methods

Results

Discussion

Conclusion