Palaeoecological evidence for changes over the past 200 years in chironomid communities of a shallow lake exposed to cyanobacterial toxins

Abstract

In spite of the existence of a number of papers applying the biomarker approach using pigments or akinetes to discuss the impact of cyanobacteria on the functioning of lakes in the palaeoenvironmental context, their sedimentary imprint in the form of microcystins (MCs) has never been taken into consideration. Our objective was to reconstruct 200 years of the development of chironomid assemblages in a shallow Polish lake with notoriously blooming toxic cyanobacteria. A 50-cm long sediment core sampled from the central part of the lake was sliced every 1 cm, dated, and analysed for the subfossil remains of Chironomidae and concentrations of MCs. The fauna underwent four distinct stages in its recent history: three periods when the assemblages were typical of hypertrophic conditions (the first one comprising the entire nineteenth century, and the second and third one including approximately the last 30 years of the twentieth century), separated by a ''eutrophic'' assemblage during the first 70 years of the twentieth century. The typical features of the ''eutrophic'' midge assemblage were high total densities and high values of taxonomic richness and diversity. This period coincided with relatively low concentrations of MCs in the sediments. Sediments from the hypertrophic periods were distinguished by taxonomic impoverishment of chironomids, low Shannon diversity index, a strong decrease in chironomid numbers, and high concentrations of MCs. Significant negative correlations with MCs along the sediment profile were observed for eurytopic chironomids. MC concentrations were also negatively but not significantly correlated with total density of chironomids, their benthic and epiphytic assemblages, species richness, and diversity index.

Feeding by two closely related species of Chironomus (Diptera: Chironomidae) in south Baltic lagoons, with implications for competitive interactions and resource partitioning

“…Microscopic algae, especially diatoms, are often rich in protein and essential fatty acids and may therefore be considered as high-quality food for growing larvae (Kajak and Warda 1968;Johannsson and Beaver 1983;Ahlgren et al 1997;Goedkoop et al 1997;Gullberg et al 1997;Dukowska et al 1999;Vos et al 2000). Cyanotoxins in turn can be accumulated in the tissues of chironomid larvae with no visible damage to the community, constituting an important vector of toxins to higher levels in aquatic food chains (Kaczorowska and Kornijów 2012;Toporowska et al 2014).…”

Can phytoplankton blooming be harmful to benthic organisms? The toxic influence of Anabaena sp. and Chlorella sp. on Chironomus riparius larvae

“…A study by Palus et al (2007) reported a slight increase in DNA damage and frequency of micronuclei in human lymphocytes induced by selected cyanobacterial extracts (Microcystis aeruginosa, Aphanizomenon flos-aquae, Pseudoanabaena sp., and Anabaena sp.). In previous research on microalgae and micrograzer interaction (Berry et al, 2008;Kaczorowska and Kornijów, 2012;Toporowska et al, 2014), it was shown that the ingestion of different toxinproducing cyanobacteria can lead to the accumulation of toxins in Chironomus spp. larvae, as well as mortality and a decreased growth rate in Daphnia.…”

A Review on the Study of Cyanotoxins in Paleolimnological Research: Current Knowledge and Future Needs

“…While records of historic MC production are slowly being produced and timelines are being extended, a comprehensive extraction technique and a detailed understanding of MC degradation and transformation post-deposition have yet to be established. As shown, the sedimentary MC content in the successive layers of sediment can demonstrate variability with no general trend of decrease [61,64]. This indicates that tracking their sedimentary content can be a reliable tool for following fluctuations in the development of MC-producers in the past.…”