Using DNA metabarcoding for assessing chironomid diversity and community change in mosquito controlled temporary wetlands

Abstract

The biocide Bacillus thuringiensis var. israelensis (Bti) is widely applied for mosquito control in temporary wetlands of the German Upper Rhine Valley. Even though Bti is considered environmentally friendly, several studies have shown non-target effects on chironomids, a key food resource in wetland ecosystems. Chironomids have been proposed as important indicators for monitoring freshwater ecosystems, however, morphological determination is very challenging. In this study, we investigated the effectiveness of metabarcoding for chironomid diversity assessment and tested the retrieved chironomid operational taxonomic units (OTUs) for possible changes in relative abundance and species diversity in relation to mosquito control actions in four temporary wetlands. Three of these wetlands were, for the first year after 20 years of Bti treatment, partly left Bti-untreated in a split field design, and one wetland has never been treated with Bti. Our metabarcoding approach detected 54 chironomid OTUs across all study sites, of which almost 70% could be identified to species level comparisons against the BOLD database. We showed that metabarcoding increased chironomid species determination by 70%. However, we found only minor significant effects of Bti on the chironomid community composition, even though Bti reduced chironomid emergence by 65%. This could be due to a time lag of chironomid recolonization, since the study year was the first year of Bti intermittence after about 20 years of Bti application in the study area. Subsequent studies will have to address if and how the chironomid community composition will recover further in the now Bti-untreated temporary wetlands to assess effects of Bti.

DNA barcoding of Chironomidae from the Lake Skadar region: Reference library and a comparative analysis of the European fauna

“…Chironomidae are well known and have historically been used as bioindicator of freshwater quality across Europe (Free et al, 2009;Nicacio & Juen, 2015;Skoulikidis et al, 2009). The development of resources for species-level identification is fundamental in this case, as only some species of Chironomidae, more sensitive to changes in the environment, are good bioindicators of freshwater quality (Lencioni et al, 2012;Theissinger et al, 2018).…”

DNA metabarcoding from sample fixative as a quick and voucher-preserving biodiversity assessment method

“…The potential of this approach is illustrated by the fact that 29 of the 62 via BOLD species-level-identified chironomids are still missing in the German Barcode of Life reference database (as of 21 March 2018) and were therefore identified by DNA sequence comparisons to material from other countries. Theissinger et al (2018) recently showed how valuable species level knowledge on chironomids would be, as several species are indicators for good water quality (low saprobic values), but they are most often lumped together as Chironomus sp. with a high saprobic value indicative for bad water quality.…”

Role of Chironomus plumosus (Diptera, Chironomidae) Population in the Central Zone of the Shallow Lake Trasimeno (Italy)

“…Chironomids are a highly diverse group, both taxonomically and ecologically, often dominating freshwater ecosystems in terms of abundance, biomass, and species richness [1][2][3][4]. They constitute the freshwater insect family with the highest number of species, both in lentic and lotic habitats [5].…”

“…Chironomids play a primary role in the ecosystem trophic chain: their aquatic preimaginal phase serves as food for fishes and invertebrates, and their subaerial adult phase as food for amphibians, reptiles, bats, and birds [4,6,7].…”

“…Bti is an entomopathogenic bacterium that produces an endotoxin affecting young chironomid larvae. It is an alternative means of control with lower toxicological impact and is more eco-compatible compared to normal synthetic insecticides [3,4,8].…”