Karina Inostroza

Soil eukaryotes, including fungi, protists, plants, and animals, are central to biosphere functioning and resilience. The Global Standardised Soil Eukaryome Dataset (GloSED) is the first dataset encompassing the entire spectrum of soil eukaryotes, covering 4,063 sampling sites in 121 countries on all continents, revealing nearly one million operational taxonomic units. All samples were collected and analysed using a standardised protocol minimizing technical biases. Long-read sequencing of full-length ITS and 18S-V9 regions provide broad taxonomic coverage and high-resolution identification supported by specialist curation of “dark taxa”. A rigorous bioinformatic processing ensures against homopolymer errors, PCR-mediated chimeras, and index switching providing high data quality. The dataset is supported by raw sequences and an open-source containerised workflow for reproducible analyses. The samples are accompanied by land-cover description and directly measured soil pH, δ ¹³ C, δ ¹⁵ N, as well as P, K, Ca, Mg, and total C and N contents. GloSED is the first database that enables ecological and biogeographic studies of entire soil eukaryotic communities from local to global scales.

The variability in stocks and accumulation rates of organic carbon (C_org), nitrogen (N), and carbonate (CaCO₃) was studied in fifteen Posidonia oceanica meadows spread throughout the South Aegean Sea (Greece). In addition, the abiotic and biotic drivers determining the pattern of variability in the accumulation rates were assessed by exploring the influence of sediment characteristics, seagrass traits, and environmental settings. The meadows supported on average (±STDEV) 14.6 ± 5.0 kg C_org m⁻², 0.47 ± 0.17 kg N m⁻², and 249 ± 210 kg CaCO₃ m⁻² in the top meter of their sediments, with mean accumulation rates over the last 500 years of 33.6 ± 23.6 g C_org m⁻² yr⁻¹, 1.00 ± 0.62 g N m⁻² yr⁻¹, and 405 ± 336 g CaCO₃ m⁻² yr⁻¹ across sites. A redundancy analysis (RDA) explained 70% of the variation in C_org, N, and CaCO₃ accumulation rates, with three sediment characteristics (i.e., sediment C_org:N and C_org:C_inorg ratios and P. oceanica contribution to the sediment C_org pool) emerging as the primary set of factors shaping the accumulation of matter, followed by seagrass traits (i.e., leaf biomass and rhizome elongation) and environmental variables (i.e., suspended organic matter). The high degree of variability within the region emphasizes the need for fine‐scale assessments to understand the local conditions influencing sequestration. Our findings underscored the critical role of seagrass meadows in carbon and nitrogen sequestration in the region, urging conservation efforts to protect these ecosystems and prevent potential losses of stored carbon and nitrogen following seagrass degradation.