Taxonomic diversity and abundance of enchytraeids (Annelida, Clitellata, Enchytraeida) in the Northern Palaearctic. 2. European Russia

Description

The diversity and abundance of small soil oligochaetes – enchytraeids, were studied in the terrestrial ecosystems of various biomes within European Russia, part of the Northern Palaearctic. Soil samples were collected in the Russian part of the East European Plain, Caucasus region, Novaya Zemlya Archipelago and Franz Josef Land. A total of 204 georeferenced sites were investigated, spanning 5 biomes classified by WWF (Olson et al., 2001): tundra, boreal forest, temperate broadleaf and mixed forest, temperate grassland, savanna and shrubland, and desert and xeric shrubland. This effort resulted in the collection of 73 species belonging to 17 genera of enchytraeids.

Geographic Coverage

This dataset presents the distribution and abundance of soil enchytraeids in the European part of the Northern Palaearctic.

Temporal scope

April 27, 2019 – July 21, 2023

Taxonomic scope

Enchytraeids from terrestrial ecosystems in the European Russia part of the Northern Palearctic.

kingdom

phylum

class

order

family

Animalia

Annelida

Clitellata

Enchytraeida

Enchytraeidae

Methodology

Study extent

The study sites were located in undisturbed zonal ecosystems across the five biomes studied (Olson et al., 2001). The number of sites varied across biomes due to differences in sampling effort and logistical availability: 22 sites in tundra, 46 in boreal forests, 84 in temperate broadleaf and mixed forests, 42 in temperate grasslands, savannas, and shrublands, and 10 in desert and xeric shrublands. Sampling sites were selected in areas with minimal signs of human disturbance, and in arid regions, we focused on the most well-watered (yet non-flooded) locations.

Sampling

The sampling protocol followed widely accepted methods in soil zoology and ecology (Ghilarov 1975, Coleman et al., 2004). Soil monoliths for studying enchytraeids were collected using a 5 cm diameter steel corer, reaching a depth of 10 cm. At each site, between 1 to 8 soil monoliths were sampled. After collection, soil monoliths were carefully transferred into plastic bags and transported to the laboratory at the A.N. Severtsov Institute of Ecology and Evolution using isothermal containers. The soil samples were stored at 4°C in a refrigerator until the extraction process. Enchytraeids were extracted from the soil using the wet funnel method (Didden et al., 1995). A sieve was placed within each funnel, with a soil monolith in each sieve. Tap water was poured into the funnel until the soil monolith was fully submerged. Each funnel was equipped with a test tube, which was then immersed in a bowl of room temperature water to prevent overheating of the extracted enchytraeids. The extraction process lasted between 16 to 24 hours. After extraction, the tubes were separated from the funnels, and their contents were emptied into petri dishes.

Quality control

A total of 73 species belonging to 17 genera of enchytraeids, were collected. Enchytraeid species were identified in vivo immediately after the extraction procedure, following the guidelines of Schmelz and Collado (2010). For species not covered in this guide or described subsequently, original descriptions were used for comparison.

The taxonomy of the identified enchytraeids has been standardized with the WoRMS database (Martin et al., 2024). Scientific names were further validated using the GBIF species matching tool. Since most individuals were used for in vivo identification without permanent preparation, for subsequent isotopic analysis, all instances of enchytraeid occurrences within the studied sites were documented as dwc:basisOfRecord=HumanObservation. Juvenile specimens were identified to the genus level. All enchytraeids were identified by Maxim Degtyarev.

Step Description

1) The selection of study sites was driven by the intention to locate undisturbed areas displaying minimal or no signs of human activity.

2) Site sampling was carried out at a distance of no less than 100 m from the borders of selected zonal sites within one of the seven biome types according to WWF (Olson et al. 2001).

3) At each site, soil monoliths were collected using a steel corer with a diameter of 5 cm, reaching a depth of 10 cm.

4) The transportation of soil monoliths was conducted in isothermic containers to prevent soil overheating, which could lead to the mortality of organisms present.

5) Enchytraeids were extracted from the soil using the wet funnel method as described by Didden et al. 1995.

6) Following the extraction procedure, enchytraeids were identified in vivo to the species level using an Olympus BX-43 microscope. Subsequently, they were preserved in 96% alcohol for further isotopic analyses.

7) Identified individuals were counted to determine abundance within the 10 cm soil core and then extrapolated from a 5 cm diameter to 1 m². Extrapolation was performed by multiplying the number of individuals by a coefficient of 512 to account for sampling bias induced by the slight ellipsoidality of the corers, which arises from their production technology peculiarities. Given the variance in the number of soil monoliths across sites, the dataset includes abundance expressed as individuals per square meter.

Funding

Sampling, identification and preparation of the dataset were funded by the Russian Science Foundation, grant No. 21-14-00227 "Soil-living Enchytraeids of the Northern Palaearctic".

Sampling on the Novaya Zemlya archipelago was carried out during an expedition supported by a grant from the Russian Geographical Society 2022; preliminary sample preparation was conducted as part of the state task of Murmansk Marine Biological Institute of the Russian Academy of Sciences (MMBI RAS).

Sampling on the Franz Josef Archipelago was conducted as part of the Arctic Century Expedition 2021, a joint initiative led by the Swiss Polar Institute (SPI), the Antarctic and Arctic Research Institute (AARI), and the GEOMAR Helmholtz Centre for Ocean Research Kiel (GEOMAR), funded by the Swiss Polar Foundation.

Sampling was also carried out as part of the Arctic Floating University expedition 2021.