Abstract

BackgroundZooplankton is an important component of aquatic organisms and has important biological and economical significance in freshwater ecosystems. However, traditional methods that rely on morphology to classify zooplankton require expert taxonomic skills. Moreover, traditional classification methods are time-consuming and labor-intensive, which is not practical for the design of conservation measures and ecological management tools based on zooplankton diversity assessment.MethodsWe used DNA metabarcoding technology with two different markers: the nuclear small subunit ribosomal RNA (18S rRNA) and mitochondrial cytochrome c oxidase (COI), to analyze 72 zooplankton samples collected in 4 seasons and 9 locations from the Sanmenxia Reservoir. We investigated seasonal changes in the zooplankton community and their relationship with water environmental factors.ResultsA total of 190 species of zooplankton were found, belonging to 12 phyla, 24 classes, 61 orders, 111 families, and 174 genera. Protozoa, especially ciliates, were the most diverse taxa. Richness and relative abundance of zooplankton showed significant seasonal changes. Both alpha and beta diversity showed seasonal trends: the diversity in summer and autumn was higher than that in winter and spring. The zooplankton diversity was most similar in winter and spring. By correlating metabarcoding data and water environmental factors, we proved that water temperature, chemical oxygen demand, total nitrogen and ammoniacal nitrogen were the main environmental factors driving the seasonal changes in zooplankton in the Sanmenxia Reservoir. Water temperature, followed by total nitrogen, were the most influential factors. This study highlights the advantages and some limitations of zooplankton molecular biodiversity assessment using two molecular markers.

Highlights

  • Protecting the biodiversity of freshwater ecosystems is important in the 21st century

  • DNA metabarcoding of zooplankton samples resulted in the identification of 495 operational units (OTUs) from the 18S rRNA gene, and 1099 OTUs from the c oxidase (COI) gene

  • 64.44% (319 of 495 OTUs, 18S rRNA) and 35.94% (395 of 1099 OTUs, COI) of the OTUs were classified as zooplankton, and the remaining OTUs were annotated as Insecta, Gastropoda, etc. (Table S3)

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Summary

Introduction

Protecting the biodiversity of freshwater ecosystems is important in the 21st century. Freshwater ecosystems contain the most concentrated biodiversity of all ecosystems on the planet but are the most endangered ecosystems worldwide (Dudgeon et al, 2006). These ecosystems are susceptible to anthropogenic factors, such as climate. DNA metabarcoding of zooplankton communities: species diversity and seasonal variation revealed by 18S rRNA and COI. Richness and relative abundance of zooplankton showed significant seasonal changes. By correlating metabarcoding data and water environmental factors, we proved that water temperature, chemical oxygen demand, total nitrogen and ammoniacal nitrogen were the main environmental factors driving the seasonal changes in zooplankton in the Sanmenxia Reservoir. This study highlights the advantages and some limitations of zooplankton molecular biodiversity assessment using two molecular markers

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