Species Diversity and Driving Factors of Benthic and Zooplanktonic Assemblages at Different Stages of Thermokarst Lake Development: A Case Study in the Lena River Delta (Middle Siberia)

Abstract

Global climate change might result in permafrost thaw and the formation of thermokarst landscapes that release long-term carbon stocks as greenhouse into the atmosphere, thereby initiating a positive climate feedback. These processes are mediated by biological activity, including by microbes, vascular plants and animals, whereas the role of invertebrates in thermokarst ecosystems remains poorly understood. We investigated the diversity and assemblage structures of zooplankton (mainly Copepoda, Cladocera), microbenthos (testate amoebae) and meio- (Copepoda and Cladocera) and macrozoobenthos (mollusks, crustaceans, insects and annelids) from a range of water bodies representing different stages of thermokarst lake formation in the southern part of the Lena River Delta (Central Siberia). Altogether, 206 species of testate amoeba, mollusk, crustacean, insect and annelid taxa were identified. A total of 60 species of macrozoobenthos (mainly insects) and 62 species of testate amoebae were detected in the water bodies of the Lena River Delta for the first time. The species richness of zooplankton and meio- and macrozoobenthos was greater in the large thermokarst lakes than in the polygonal ponds due to the freezing of the latter in the winter. In contrast, the species richness of protists was higher in the polygonal ponds, which was related to the habitat preferences of testate amoebae. Fish grazing strongly affected the macrobenthos assemblages but not the smaller-sized organisms. Water acidity and temperature were the main environmental drivers of the assemblage structure of testate amoeba and microcrustacean. The species structure of the macroinvertebrate assemblages was significantly explained by water acidity, permafrost depth and size of the water area. It means that small size organisms with their short generation times are sensitive to more dynamic factors such as temperature and may serve as indicators of ecosystem changes due to global climate warming. In contrast, large size organisms are affected by driven factors that appear during thermokarst lakes formation and permafrost degradation.

The Influence of Salinity Gradient and Island Isolation on Fauna Composition and Structure of Aquatic Invertebrate Communities of the Shantar Islands (Khabarovsk Krai)

“…Once a species has accidentally entered a water body, it "monopolizes" it through rapid adaptation to environmental conditions and the provision of a large resting propagule bank, which can act as a powerful barrier to the invasion of competitors [112]. Similar trends have been observed in the formation of zooplankton communities in isolated water bodies [82,113].…”

“…In this context, the biogeographic structure of the zooplankton and meiobenthos fauna is collectively considered. The presented distributional types of microcrustaceans are based on Kotov A.A.'s descriptions for Cladocera [81,82], which were further extended for Copepoda [3]. The fauna of the Shantar Islands is predominantly represented by species with wide Palaearctic (46.3% of the total species richness), Holarctic (10.1%), and cosmopolitan (24.6%) ranges.…”

“…This may be due to the lower adaptability of Ctenopoda to the freezing of water bodies and settlement on waterfowl compared to Anomopoda. The main reason for this may be the absence of ephippium in representatives of the suborder, which increases the viability of resting eggs [82].…”

Resettlement of Eurytemora velox (Crustacea: Copepoda) in Europe, the Urals and Western Siberia

“…far [15,16]. In particular, E. velox is not found in the zooplankton of the Lena Delta [17][18][19], although the region has been quite well sampled and studied in recent years due to many ecological programs in the location of the Lena Delta Nature Reserve.…”

Meiofauna: Biodiversity, Ecology, and Role in Ecosystems

“…On the plateau, the glacial domes were located only on flat ridge tops, while the lakes in the valleys preserved the refugia of Pleistocene fauna. The article by Chertoprud et al [17] describes a change in the complexes of dominant species in the communities of micro-, meio-, and macrozoobenthos, as well as zooplankton, during the development of thermokarst tundra water bodies in the Lena River delta. The meiobenthos in these water bodies is mainly represented by microcrustaceans (Cladocera and Copepoda).…”