10.25607/bgjoog afdf89d6-4aa9-41e1-bc3d-cee33befa66c https://ipt.obis.org/bioecoocean/resource?r=biodiversity_survey_gotland_summer_2021 Lina Mtwana Nordlund Uppsala University

Visby SE

lina.mtwana.nordlund@geo.uu.se Florian Lüskow Uppsala University

Visby SE

florian.luskow@geo.uu.se https://orcid.org/0000-0002-2100-7012 Elizabeth Lawrence IOC-UNESCO/OBIS Secretariat

CA

e.lawrence@unesco.org https://orcid.org/0000-0002-5304-941X 2026-06-21 eng eDNA sampling of invertebrates in summer 2021 around Gotland, the central Baltic Sea Samplingevent GBIF Dataset Type Vocabulary: http://rs.gbif.org/vocabulary/gbif/dataset_type_2015-07-10.xml Benthic invertebrates: http://vocab.nerc.ac.uk/collection/EXV/current/EXV068/ Zooplankton: http://vocab.nerc.ac.uk/collection/EXV/current/EXV057/ NERC EV Terms: http://vocab.nerc.ac.uk/collection/EXV/current/ This work is licensed under a Creative Commons Attribution Non Commercial (CC-BY-NC 4.0) License. Creative Commons Attribution Non Commercial 4.0 International https://spdx.org/licenses/CC-BY-NC-4.0.html CC-BY-NC-4.0 Coastal waters of Gotland in the central Baltic Sea 16.831 20.786 58.654 56.253 2021-07-27 2021-09-08 asNeeded Lina Mtwana Nordlund Uppsala University

Visby SE

lina.mtwana.nordlund@geo.uu.se https://orcid.org/0000-0002-4450-2331 The analytical workflow followed a standardised marine eDNA metabarcoding pipeline: - DNA extraction & purification: DNA was extracted from the filters using a commercial kit with a modified protocol to maximise yields and purified to remove PCR inhibitors - PCR amplification: the V4–V5 region of the 18S rRNA gene was targeted to capture a broad range of invertebrates. Standard analysis included three PCR replicates per sample - Library preparation & sequencing: PCR amplicons were purified, quantified using a Qubit broad-range kit, and pooled into a final library at equal concentrations; sequencing was performed on an Illumina MiSeq V3 kit (10.5 pM) with a 20% PhiX spike-in - Bioinformatics & taxonomic assignment: Sequences were processed through a custom pipeline for quality filtering and Operational Taxonomic Unit (OTU) clustering. Taxonomic assignments were made by comparing consensus sequences against the NCBI nt and SILVA 18S (v138.1) databases, using the GBIF taxonomic backbone for consistency; minimum similarity thresholds were set at 98% for species, 95% for genus, and 92% for higher taxonomic levels - Data filtering & analysis: The final dataset was filtered to remove low-abundance OTUs (< 0.025% or < 10 reads) and common contaminants; for multivariate analysis, OTU data were transformed into presence–absence data to account for biological and methodological biases in read proportions This study characterises the coastal brackish-water invertebrate diversity around the island of Gotland, Sweden, in the central Baltic Sea. Sampling was conducted during the summer of 2021 (July–September) at three distinct coastal sites: Kappelshamnsviken (northwest coast), Lergrav, and Valleviken (northeast coast). The study focussed on shallow coastal margins where bottom depths are generally less than 5 m. The environmental setting of the study area is characterised by relatively stable, low-to-intermediate salinity (range 4.2–6.7) and varying sub-surface temperatures (range 12.1–19.7°C). The taxonomic scope covers 42 marine invertebrate taxa across eight animal phyla, including both pelagic (holoplanktonic and meroplanktonic) and benthic assemblages. Environmental DNA (eDNA) water samples were collected using a stratified random sampling approach to ensure coverage across distinct areas of the coastal bays. At each of the three sites, three separate 5-litre water samples were collected from a depth of < 0.5 m below the surface, either from a boat or by snorkelling. Samples were immediately stored on ice in cooler boxes for transport. In the laboratory, 500 ml from each 5-litre collection was filtered through a Nalgene® analytical filter funnel with a 0.45 µm pore size. The resulting filters were preserved in 200-proof ethanol and stored at -20°C until further processing. At the time of collection, in situ measurements for temperature, salinity, and dissolved oxygen were recorded using a handheld Elma 795 Multi Chemistry instrument. Lina Mtwana Nordlund https://orcid.org/0000-0002-4450-2331 processor 2026-06-18T14:48:22.196+00:00 dataset Nordlund L M, Lüskow F, Lawrence E (2026). Invertebrate eDNA Gotland Summer 2021. Version 2.1. OBIS Secretariat. Samplingevent dataset. https://doi.org/10.25607/bgjoog afdf89d6-4aa9-41e1-bc3d-cee33befa66c/v2.1.xml