Short comment on chironomid assemblages and stratigraphy of high altitude lakes from Tibet

A recent chironomid record of three shallow, high altitude lakes in southern Tibet, as well as a short palaeolimnological history of one lake, are presented. The recent chironomid assemblages consisted of 13 taxa; one of the Orthocladiinae taxa recorded most likely represents a new species. In spite of the low head capsule concentration in the sediment core of Lake Karuugema, probably due to physical disturbance, redistribution and outwash of head capsules, there was a trend from assemblages composed of stenothermal/rheophilic taxa to eurythermal/limnophilic taxa. This shift in assemblage structure suggests that changes in monsoon precipitation and catchment hydrology may have influenced the habitat conditions of the chironomids

Checklist of benthic macroinvertebrates of high altitude ponds of the Tatra Mountains (Central Europe) with new records of two species for Slovakia

A checklist of benthic macroinvertebrates of ponds of Tatra Mountains is presented. The checklist comprises 122 taxa including the first records of Derotanypus cf. sibiricus (Kruglova & Chernovskii, 1940) (Diptera: Chironomidae) and Arctocorisa carinata (Sahlberg, 1918) (Heteroptera) from Slovakia. The most diverse pond site supported 28 taxa, the minimum number of recorded taxa was 2. The richest group was Chironomidae (Diptera) constituting almost half of the total diversity (58 taxa), followed by Trichoptera with 15 taxa. The other higher taxonomic groups were represented by considerably lower taxa number. Relatively high number of recorded taxa underlines important contribution of small lentic waterbodies to regional biodiversity of high-altitude ecosystems

Subfossil Chironomidae (Diptera) in surface sediments of the sinkholes (cenotes) of the Yucatan Peninsula: Diversity and distribution

Cenotes (sinkholes), formed by the dissolution of the carbonate rock, are the most common waterbodies on the Yucatan Peninsula. Despite their unique features and great amount in the region, our knowledge on the biota of cenotes remains fragmentary. Within the present study we analysed chironomid remains from surface sediment of ten cenotes situated in SE Mexico. In total, 20 taxa of 17 genera were recorded, and the total diversity was estimated to ~30 taxa. The most common taxa were Polypedilum (Tripodura) sp., Tanytarsus ortoni-type, Fittkauimyia sp., Labrundinia sp. and Endotribelos sp. There was a great variability in head capsule abundance among cenotes, ranging from 1 to 64 individuals per site with significantly higher number of remains recorded in open cenotes compared to the closed, cavern types. The results indicate that beside ecological features, such as low trophy, oxygen depletion, simplified habitat structure and fish predation, there are also taphonomical processes connected to the specific nature of cenotes that can hinder the accumulation of biological remains in the sediment. We conclude that due to poor sedimentation and preservation of remains, cenotes have limited potential for palaeolimnological studies

Imprints of the Little Ice Age and the severe earthquake of AD 2001 on the aquatic ecosystem of a tropical maar lake in El Salvador

Using a 530-year sediment record from the maar Lake Apastepeque, El Salvador, and based on diverse geochemical and biological (cladocerans, chironomids, diatoms, ostracods, testate amoebae) indicators, we estimated climatic and environmental alterations during the Little Ice Age (LIA) and reconstructed the recent history of the lake. Results demonstrate relatively humid conditions in the mid-elevations (500 m a.s.l.) of El Salvador during most parts of the LIA, resulting in high lake levels. Contrarily, the first part of the LIA was characterized by drier climates comparable to studies from Mexico and Belize, which correlated this phase with the Spörer minimum. Regional comparison with palaeorecords from the northern Neotropics reveals a high heterogeneity in local expressions of the LIA in Central America, likely connected to the high topographic heterogeneity of the region. Since the beginning of the 20th century, Lake Apastepeque has experienced enhanced human impact expressed as increased nutrient supply. The most recent period was characterized by significant environmental disturbance, which we relate to an upper-crustal earthquake, one of the strongest over the last 500 years, that affected the region on 13th February 2001 (Mw = 6.6, epicentre at 10 km depth, 30 km from the lake). The release of toxic bottom components such as hydrogen sulphide and high turbidity and turbulence of water caused major species turnover in the lake ecosystem, resulting in a massive fish kill and colonization by large cladocerans. Modern sediments still show slightly altered biota communities compared to pre-earthquake assemblages, indicating that the ecosystem has still not fully recovered

The distribution of littoral chironomids along an altitudinal gradient in High Tatra Mountain lakes: Could they be used as indicators of climate change?

We studied assemblages of littoral chironomids from three alpine lakes in the High Tatra Mountains (Slovakia) along an altitude range of 1725–2157 m. The study sites were selected in order to emphasize differences in their thermal regimes. Littoral samples were taken quantitatively in the ice-free seasons of 2000 and 2001. In total, 3468 chironomid larvae and pupae were collected and 32 taxa were identified. Some parameters of the littoral chironomid assemblages showed clear patterns along the altitude gradient. The number of taxa and Shannon diversity increased markedly with decreasing altitude. Density, however, did not show any correlation with altitude. Even though gatherers highly dominated in all sites, their relative abundance decreased with decreasing altitude. The ratio of scrapers and predators correlated negatively with altitude. According to the results of a Detrended Correspondence Analysis, Pseudodiamesa arctica and Micropsectra radialis were chosen as indicator species for alpine lakes >2000 m a.s.l. Typical subalpine lake inhabitants are Zavrelimyia sp., Prodiamesa olivacea, Corynoneura scutellata group, Cricotopus polaris, Micropsectra bavarica and Paratanytarsus austriacus. A single species, Micropsectra junci, seemed to be characteristic of alpine lakes <2000 m a.s.l. This “gradient lake concept” could be used to predict changes in mountain lake fauna under expected climate change scenarios. Generally, an upward shift of subalpine species would be expected. The thermal regime of lakes, however, also depends on several local factors. Consequently, the schemes outlined here would not be valid for the entire Tatra lake district

Subfossil chironomids (Diptera, Chironomidae) of lakes in the Tatra Mountains an illustrated guide

Chamutiová, Tímea, Hamerlík, Ladislav, Bitušík, Peter (2020): Subfossil chironomids (Diptera, Chironomidae) of lakes in the Tatra Mountains an illustrated guide. Zootaxa 4819 (2): 216-264, DOI: https://doi.org/10.11646/zootaxa.4819.2.

First record of the genus Anatopynia Johannsen, 1905 (Diptera, Chironomidae) from Slovakia, in a semi-permanent oxbow lake

We present the first record of Anatopynia plumipes (Fries, 1823) from Slovakia. Larva of this species was found in a semi-permanent oxbow lake, a remnant of a plesiopotamal-type side arm of the Danube River

FIGURE 2 in Chironomidae (Diptera) of Croatia with notes on the diversity and distribution in various habitat types

FIGURE 2. Frequency of occurrence of chironomid species recorded on five or more sites.Published as part of Čerba, Dubravka, Koh, Miran, Ergović, Viktorija, Mihaljević, Zlatko, Milošević, Djuradj & Hamerlík, Ladislav, 2020, Chironomidae (Diptera) of Croatia with notes on the diversity and distribution in various habitat types, pp. 259-274 in Zootaxa 4780 (2) on page 262, DOI: 10.11646/zootaxa.4780.2.2, http://zenodo.org/record/399076

Flooding and hydrologic connectivity modulate community assembly in a dynamic river-floodplain ecosystem

International audienceBraided river floodplains are highly dynamic ecosystems, where aquatic communities are strongly regulated by the hydrologic regime. So far, however, understanding of how flow variation influences assembly mechanisms remains limited. We collected benthic chironomids and oligochaetes over a year across a lateral connectivity gradient in the semi-natural Tagliamento River (Italy). Four bankfull flood events occurred during the study, allowing the assessment of how flooding and hydrologic connectivity mediate the balance between sto-chastic and deterministic community assembly. While invertebrate density and richness were positively correlated with connectivity, diversity patterns showed no significant correlation. Species turnover through time increased with decreasing connectivity. Contrary to expectations, hydrologic connectivity did not influence the response of community metrics (e.g. diversity, density) to floods. Invertebrate composition was weakly related to connectiv-ity, but changed predictably in response to floods. Multivariate ordinations showed that faunal composition diverged across the waterbodies during stable periods, reflecting differential species sorting across the lateral gradient, but converged again after floods. Stable hydrological periods allowed communities to assemble deterministically with prevalence of non-random beta-diversity and co-occurrence patterns and larger proportion of composi-tional variation explained by local abiotic features. These signals of deterministic processes declined after flooding events. This occurred despite no apparent evidence of flood-induced homogenisation of habitat conditions. This study is among the first to examine the annual dynamic of aquatic assemblages across a hydrologic connectivity gradient in a natural flood-plain. Results highlight how biodiversity can exhibit complex relations with hydrologic con-nectivity. However, appraisal of the assembly mechanisms through time indicated that flooding shifted the balance from deterministic species sorting across floodplain habitats, towards stochastic processes related to organisms redistribution and the likely resetting of assembly to earlier stages