Preliminary Analysis Suggests Freshwater Invertebrate Environmental Dna Is More Concentrated in Surface Water Than in Benthic Sediments

Abstract

The collection, identification, and census of freshwater invertebrates helps to increase understanding of the ecological function of lakes and streams. However, this work can be time-consuming and laborious because invertebrate identification often requires considerable taxonomic training and expertise. The collection and analysis of environmental DNA (eDNA), the genetic material that organisms shed into their surrounding environment, represents a potentially revolutionary approach for rapid and accurate invertebrate surveillance in freshwater environments. Previous studies have demonstrated that fish eDNA tends to be more abundant in freshwater lake sediments than the water column above, so we conducted an experiment to examine whether this pattern holds true for freshwater invertebrates. We collected paired samples from benthic sediments and the water column at ten sites around an urban playa lake in Lubbock, Texas. Based on cycle threshold values from quantitative PCR (qPCR) amplification with universal invertebrate primers targeting the COI gene, a paired Wilcoxon signed-rank test and Spearman rank-order correlation suggested that invertebrate eDNA quantities were correlated between the sediment and water column but consistently more concentrated in the water compared to the sediment below, directly contrasting with previous studies of fish eDNA. Future work combining eDNA detection and high-throughput sequencing (i.e., metabarcoding) will increase understanding of how eDNA signals relate to local invertebrate pools and increase the utility of eDNA sampling for freshwater invertebrates.