DNA metabarcoding reveals the complex and hidden responses of chironomids to multiple stressors

Abstract

Background: Chironomids, or non-biting midges, often dominate stream invertebrate communities in terms of biomass, abundance, and species richness and play an important role in riverine food webs. Despite these clear facts, the insect family Chironomidae is often treated as a single family in ecological studies or bioassessments given the difficulty to determine specimens further. We investigated stressor responses of single chironomid operational taxonomic units (OTUs) to three globally important stressors (increased salinity, fine sediment and reduced water flow velocity) in a highly replicated mesocosm experiment using a full-factorial design (eight treatment combinations with eight replicates each). Results: In total, 183 chironomid OTUs (97% similarity) were obtained by applying a quantitative DNA metabarcoding approach. Whereas on the typically applied family level, chironomids responded positively to added fine sediment and reduced water velocity in the streambed and negatively to reduced velocity in the leaf litter, an OTU-level analysis revealed a total of 15 different response patterns among the 35 most common OTUs only. The response patterns ranged from (a) insensitivity to any experimental manipulation over (b) highly specific sensitivities to only one stressor to (c) additive multiple-stressor effects and even (d) complex interactions. Conclusion: Even though most OTUs (> 85%) could not be assigned to a formally described species due to a lack of accurate reference data bases at present, the results indicate increased explanatory power with higher taxonomic resolution. Thus, our results highlight the potential of DNA-based approaches when studying environmental impacts, especially for this ecologically important taxon and in the context of multiple stressors.

DNA metabarcoding adds valuable information for management of biodiversity in roadside stormwater ponds

“…DNA metabarcoding is a powerful tool for identification of invertebrates (Beermann et al, 2018;Chan et al, 2014;. In our study, comparisons of morphological identification and DNA metabarcoding clearly illustrate that DNA metabarcoding was particularly beneficial for the identification of dipteran species.…”

“…Several studies have applied and compared DNA metabarcoding with morphological identification in assessments of macroinvertebrate diversity (Chan et al, 2014;Renaud, Savage, & Adamowicz, 2012). Beermann et al (2018) indicated that although, for example, in the case of chironomids, most operational taxonomic units (OTUs) (>85%) do not match with high similarity (>98%) to formally described species due to incomplete reference libraries, DNA-based approaches are still potentially useful when studying environmental impacts, especially in the context of multiple stressors.…”

“…It has been shown that the cost of, for example, midge, identification using morphological properties is quite high due to the requirement of dissection and mounting of specimens onto microscopic slides (Baloğlu et al, 2018). As a result, the rarely used species-level data lead to the undesirable information of responses to stressors, because different species have different sensitivity to environmental parameters (Baloğlu et al, 2018;Beermann, Zizka, Elbrecht, Baranov, & Leese, 2018;Macher et al, 2015).…”

Scaling up DNA metabarcoding for freshwater macrozoobenthos monitoring

“…As long as it is possible to measure the concentration of amplicons independently from primer dimers, samples can be pooled first and then subjected to clean-up. if amplicons of different length are sequenced on the same run or if the number of specimens across samples is highly variable (Beermann, Zizka, Elbrecht, Baranov, & Leese, 2018;Theissinger et al, 2018). Usually, all samples are pooled with identical amplicon concentration to ensure similar sequencing depth across all of them.…”

Mosquito control actions affect chironomid diversity in temporary wetlands of the Upper Rhine Valley

“…To further assess potential ecological consequences of the Bti‐induced chironomid abundance reduction in three temporal wetlands of the Upper Rhine Valley (Allgeier et al, ), the chironomid communities need to be assessed with higher taxonomic resolution. Chironomid taxonomy based on morphology is often subject to misclassification, but community metabarcoding has been proven to be an efficient tool to assess chironomid species diversity (Beermann, Zizka, Elbrecht, Baranov, & Leese, ; Carew, Pettigrove, Metzeling, & Hoffmann, ; Theissinger et al, ).…”