Environmental Variables Influencing Chironomid Assemblages (Diptera: Chironomidae) in Lowland Rivers of Central Poland

Response of Chironomids (Diptera, Chironomidae) to Environmental Factors at Different Spatial Scales

Factors responsible for species distribution of benthic macroinvertebrates, including responses at different spatial scales, have been previously investigated. The aim of the present research was to review the most relevant factors explaining chironomid species distribution focusing on factors operating at different spatial scales, such as latitude, longitude, altitude, substrate, salinity, water temperature, current velocity, conductivity, acidity, dissolved oxygen, nutrient content etc. acting at regional levels and at a large or small water basin level. Data including chironomid species abundances from different lentic and lotic waters in Italy and other surrounding countries were analyzed using partial canonical correspondence analysis (pCCA) and multiple discriminant analysis (DISCR). Spatial analyses, including univariate Moran's I correlograms, multivariate Mantel correlograms and Moran's eigenvector maps (MEMs), were thereafter carried out. The results showed that habitat type, including different types of lotic waters (i.e., kryal, crenal, rhithral, potamal) and different lake types (i.e., littoral, sublittoral, profundal zones), is the most significant factor separating chironomid assemblages, while spatial factors act only as indirect influencers.

Surveillance spilled Chironomidae (Diptera) larvae from drinking water treatment plants in South Korea using morphogenetic species analysis and eDNA metabarcoding

Chironomid larvae (Diptera: Chironomidae) are tremendous indicator species that can tolerate a broad range of environmental conditions, from polluted to unimpaired water ecosystems. These species are ubiquitously observed in all bioregions and can even be found in drinking water treatment plants (DWTPs). Detection of chironomid larvae in DWTPs is a critical issue because their presence may be indicative of the water quality in the supply of tap water for human consumption. Therefore, the aim of the present study was to identify the chironomid communities that reflect the water quality of DWTPs and develop a biomonitoring tool to detect biological contamination of the chironomids in DWTPs. To do so, we investigated the identity and distribution of chironomid larvae in seven DWTP areas using morphological identification, DNA barcoding, and sediment environmental DNA (eDNA) analysis. A total of 7924 chironomid individuals encompassing three subfamilies and 25 species of 19 genera were identified in 33 sites within the DWTPs. The Gongchon and Bupyeong DWTPs were dominated by Chironomus spp. larvae, which were correlated with low levels of dissolved oxygen in the water. In the Samgye DWTP and Hwajeong DWTP, Chironomus spp. were almost absent, and instead, Tanytarsus spp. were abundant. Additionally, the Gangjeong DWTP was dominated by a Microtendipes sp., and two species of Orthocladiinae (a Parametriocnemus sp. and a Paratrichocladius sp.) were found only in the Jeju DWTP. We also identified the eight most abundant Chironomidae larvae found in the DWTPs. Furthermore, eDNA metabarcoding of DWTP sediment indicated the presence of different eukaryotic fauna and confirmed the presence of chironomids in DWTPs. These data provide useful morphological and genetic information regarding chironomid larvae that can be used for the water quality biomonitoring of DWTPs to support the supply of clean drinking water.

Factors Controlling Morphotaxa Distributions of Diptera Chironomidae in Freshwaters

Many hydrobiological studies have dealt with the autecology of species within the family Chironomidae and discussed factors affecting species distribution. The aim of the present research is to consider the most important factors affecting chironomid species distribution. Habitat type (lentic, lotic, krenal, rhithral, etc.), water temperature, conductivity, and trophic status are confirmed key factors controlling their assemblage structure. Here, we introduce the term “morphotaxon” as the taxonomic level, intermediate between genus and species, more suitable to describe the ecological responses of Chironomidae. The present uncertainty related to species identification is at the base of the proposal, with the assumption that species belonging to the same morphotaxon have similar ecological needs. In this study, this hypothesis was found to be valid, with few exceptions represented by species-rich genera (e.g., Tanytarsus, Paratanytarsus). The morphotaxon can be viewed as an interim measure waiting for the implementation of new complementary approaches, such as species identification with molecular methods.

Distribution patterns of epiphytic reed-associated macroinvertebrate communities across European shallow lakes

So far, research on plant-associated macroinvertebrates, even if conducted on a large number of water bodies, has mostly focused on a relatively small area, permitting limited conclusions to be drawn regarding potentially broader geographic effects, including climate. Some recent studies have shown that the composition of epiphytic communities may differ considerably among climatic zones. To assess this phenomenon, we studied macroinvertebrates associated with the common reed Phragmites australis (Cav.) Trin. ex Steud in 46 shallow lakes using a common protocol. The lakes, located in nine countries, covered almost the entire European latitudinal range (from <48°N to 61°N) and captured much of the variability in lake size and nutrient content in the region. A Poisson Generalized Linear Mixed Model (GLMM) showed the number of macroinvertebrate epiphytic taxa to be negatively associated with water conductivity and positively associated with medium ice cover duration (approximately 1 month). A Gamma GLMM showed a positive effect of chlorophyll a on the density of macroinvertebrates, and a significantly greater density in lakes located at the lowest and highest latitudes. Individual taxa responded differently to lake environmental conditions across climate zones. Chironomidae dominated in all climate zones, but their contribution to total density decreased with increasing latitude, with progressively greater proportions of Naidinae, Asellidae, Ephemeroptera and Trichoptera. Our study demonstrates that epiphytic macroinvertebrate fauna, even when analyzed at low taxonomic resolution, exhibits clear differences in diversity, relative abundance of individual taxa and total density, shaped both by geographic and anthropogenic variables. The results were discussed in the context of climate change. To our best knowledge this is the first study to examine epiphytic fauna carried out on a European scale.