Description: Larval dispersal is a fundamental process responsible for colonization and connectivity of benthic invertebrate populations. It is difficult to study larval dispersal in polar environments because weather and climate conditions restrict sample collection to certain seasons. In this study, we leveraged oceanographic moorings as long-term scientific platforms for collecting larvae and recruits of benthic invertebrate species in the Fram Strait and along the continental slope north of Svalbard in 2017–2021. Larval traps and fouling panels were deployed at various depths on 15 moorings at 8 locations, and additional specimens of biofouling were obtained opportunistically from moored instruments. Our results showed a significant difference in species composition between samples collected in Atlantic Water in the West Spitsbergen Current (WSC) and samples collected in Arctic Water near the seafloor and in the East Greenland Current (EGC) in the western part of the Fram Strait. There was also a stark difference between Atlantic Water species in the Fram Strait and on the north Svalbard slope. Most specimens collected in the WSC belonged to species with long-duration planktotrophic larvae, such as the ubiquitous bivalve Hiatella arctica, the bryozoan Alcyonidium mamillatum, and two nudibranchs. Samplers exposed primarily to Arctic water at their given depth and location were dominated by hydrozoans. We observed medusae budding off of the hydroids Stegopoma plicatile and Rhizoragium roseum. Our study demonstrates that the WSC is an important vector for larval dispersal into the central Arctic Ocean. Integration of biological samplers on oceanographic moorings holds great promise for monitoring efforts as climate change progresses, especially in environments where research is challenging and seasonally limited, such as the Arctic. 1. Introduction For benthic invertebrates, especially those with sessile adult stages (e.g., sponges, anemones), larval dispersal is the primary mechanism of dispersal to new habitats (Pechenik, 1999). The patterns and mechanisms of larval dispersal are difficult to study in the Arctic Ocean, where weather and climate conditions restrict sample collection to summer months. As a result, larval dispersal and the subsequent processes of settlement and recruitment in benthic invertebrates are poorly understood in the Arctic Ocean, despite their importance. Oceanographic moorings provide excellent platforms for studying larval dispersal, recruitment, and growth of organisms (Chava et al., 2021; Schiaparelli and Aliani, 2019). Instruments and floats on a mooring are deployed in the water column by design, so the

Description: Time series data of physical oceanography (seawater conductivity, temperature, pressure, salinity), ocean current velocities and hydroacoustics were obtained from mooring F4-18 in the Fram Strait in July 2018 - August 2019 as part of the Helmholtz infrastructure program Frontiers in Arctic Marine Monitoring (FRAM) and the long-term monitoring program at AWI HAUSGARTEN. The mooring was deployed during Polarstern expedition PS114, and recovered during PS121. The attached archive contains raw data files of 6 Seabird SBE37 microcats (nominal depths: 63m, 150m, 250m, 500m, 731m, 1202m; sampling interval 1h), one RDI Workhorse Longranger ADCP (depth: 380m; sampling interval: 1h) and two AADI RCM11 current meters (depths: 730m, 1208m; sampling interval: 2h). The mooring also included a Develogic Sonovault (nominal depth: 800m; data archived elsewhere). Auxiliary information such as sensor calibration sheets, mooring diagrams and schedule files are also provided, if applicable.

Description: During Polarstern expedition PS131 (ATWAICE: ATlantic WAter pathways to the ICE), a large number of autonomous instruments were installed on three representative ice floes across the marginal ice zone northwest of Svalbard in July 2022. The aim was to investigate sea ice summer melt processes, with a focus on the contribution of the Atlantic water inflow into the region. The attached .zip file includes raw data files obtained from all instruments deployed on the southernmost floe, also referred to as Floe South. Depending on the instrument, the data were transmitted via satellite, collected on internal memory, or both. The instruments were installed on Floe South on 14 July 2022, revisited for maintenance on 21 July 2022, and partially recovered on 31 July 2022. The sensors included 1 ADCP to measure ocean currents, a CTD buoy (SIT) with 5 SBE37IMP, a SIMBA- and a SIMB-type ice mass balance buoy to determine ice surface and bottom melt, an OpenMetBuoy (OMB) and iridium IMU logger for wave detection, two GPS drifters, and 2 timelapse cameras to document surface changes. All instruments performed as expected. All instruments except one OpenMetBuoy were recovered before leaving the study area on 31 July. The processed data will be provided and linked to when available.

Description: Time-series data of physical oceanography and carbon/particle export were obtained from mooring HG-IV-FEVI-38 in the Fram Strait in July 2018 - August 2019 as part of the Helmholtz infrastructure program Frontiers in Arctic Marine Monitoring (FRAM) and the long-term monitoring program at AWI HAUSGARTEN. The mooring was deployed during RV POLARSTERN expedition PS114, and recovered during PS121. The attached archive contains raw data files of four Seabird SBE37 microcats (nominal depths: 52m, 253m, 1200m, 2526m; sampling interval 1h), two AADI RCM11 current meters (nominal depths: 203m, 1230m; sampling interval 1h), one Nortek Aquadopp current meter (nominal depth: 750m; sampling interval 20 min), one RDI Longranger ADCP (nominal depth: 409m; sampling interval 1h) and two AADI Seaguard current meters (nominal depths: 2348m, 2524m; sampling interval 1h). The mooring also included three sediment traps (nominal depths: 196m, 1223m, 2341m) and one BioOptical Platform (565m). Auxiliary information such as sensor calibration sheets, mooring diagrams and schedule files are also provided, if applicable.

Description: During Polarstern expedition PS131 (ATWAICE: ATlantic WAter pathways to the ICE), a large number of autonomous instruments were installed on three representative ice floes across the marginal ice zone northwest of Svalbard in July 2022. The aim was to investigate sea ice summer melt processes, with a focus on the contribution of the Atlantic water inflow into the region. The attached .zip file includes raw data files obtained from all instruments deployed on Floe Middle, located between Floe North and Floe South. Depending on the instrument, the data were transmitted via satellite, collected on internal memory, or both. The instruments were installed on Floe Middle on 15 July 2022, revisited for maintenance on 22 July 2022, and partially recovered on 31 July 2022. The sensors included 1 ADCP to measure ocean currents, a CTD buoy (SIT) with 5 SBE37IMP and 3 SBE56, a SIMBA-type ice mass balance buoy to determine ice surface and bottom melt, an OpenMetBuoy (OMB) and IMU logger for wave detection, one GPS drifter to mark the ADCP, and 3 timelapse cameras to document surface changes. All instruments performed as expected. All instruments except one OpenMetBuoy were recovered before leaving the study area on 31 July. The processed data will be provided and linked to when available.

Description: Time-series data of physical oceanography, ocean current velocities and hydroacoustics were obtained from mooring F4-19 in the Fram Strait in August 2019 - June 2021 as part of the Helmholtz infrastructure program Frontiers in Arctic Marine Monitoring (FRAM) and the long-term monitoring program at AWI HAUSGARTEN. The mooring was deployed during RV POLARSTERN expedition PS121, and recovered during PS126. The attached archive contains raw data files of 7 Seabird SBE37 microcats (nominal depths: 76m, 153m, 253m, 402m, 502m,731m, 1204m; sampling interval 1h), four Seabird SBE56 temperature loggers (nominal depths: 53m, 102m, 203m, 323m; sampling interval 30s), one upward-looking RDI Workhorse 300kHz ADCP (nominal depth: 53m; sampling interval 1h), one upward-looking RDI Workhorse Longranger ADCP (depth: 382m; sampling interval 1h) and two Nortek Aquadopp current meters (nominal depths: 730m, 1205m; sampling interval 20min). The 300 kHz ADCP stopped recording after 3 months due to a battery failure. The mooring also included an ASL Acoustic Zooplankton Fish Profiler (nominal depth: 103m; data archived elsewhere) and a Develogic Sonovault (nominal depth: 800m; data archived elsewhere). Auxiliary information such as sensor calibration sheets, mooring diagrams and schedule files are also provided, if applicable.

Description: Time-series data of physical oceanography, ocean current velocities and bio-optical seawater properties were obtained from mooring HG-IV-SWIPS-2019 (alternative name: HG-IV-W-4) in the Fram Strait in August 2019 - June 2021 as part of the Helmholtz infrastructure program Frontiers in Arctic Marine Monitoring (FRAM) and the long-term monitoring program at AWI HAUSGARTEN. The mooring was deployed during RV POLARSTERN expedition PS121, and recovered during PS126. The attached archive contains raw data files of an integrated profiling SBE52plus system (nominal depth: 125m) and a single AADI Seaguard current meter (nominal depth: 154m; sampling interval: 1h). Due to technical issues with the SWIPS winch, the associated sensors only delivered useful profiling data during the first 2 months, albeit at a higher frequency than originally planned. Auxiliary information such as sensor calibration sheets, mooring diagrams and schedule files are also provided, if applicable.

Description: Time-series data of physical & biological oceanography, ocean current velocities, nutrient biogeochemistry, molecular biology and carbon/particle export were obtained from mooring HG-EGC-7 in the Fram Strait from June 2021 to July 2022 as part of the Helmholtz infrastructure program Frontiers in Arctic Marine Monitoring (FRAM) and the long-term monitoring program at AWI HAUSGARTEN. The mooring was deployed during RV POLARSTERN expedition PS126 and recovered during PS131. The attached archive contains raw data files of three Seabird SBE37 MicroCATs (nominal depths: 38m, 232m, 484m; sampling interval 1h), three AADI RCM11 current meters (nominal depths: 45m, 239m, 487m; sampling interval 1h), one AADI Seaguard current meter (nominal depth: 993m, sampling interval 1h), one Wetlabs ECO PAR sensor (nominal depth: 38m; sampling interval 1h), one Wetlabs ECO Triplet fluorometer (nominal depth: 38m; sampling interval 2h), two Satlantics SUNA nitrate sensors (nominal depths: 38m, 232m; sampling interval 4h), two Sunburst SAMI-pCO2 sensors (nominal depths: 38m, 232m; sampling interval 1h) and two Sunburst SAMI-pH sensors (nominal depths: 38m, 232m; sampling interval 3h). The mooring also included two McLane RAS water samplers (nominal depths: 38m, 232m; data archived elsewhere), one sediment trap (nominal depth: 480m; data archived elsewhere), and four PE samplers (nominal depths: 51m, 239m, 482m, 893m; data archived elsewhere). Auxiliary information such as sensor calibration sheets, mooring diagrams, and schedule files are also provided, if applicable. The pH sensor at 38 m, the ECO Triplet at 38 m and the SUNA at 232m had issues and did not record any valid data.

Description: Time-series data of physical oceanography and ocean current velocities were obtained from mooring SCO1-1 in the Fram Strait from Aug 2018 to Aug 2022. The mooring was deployed during RV MARIA S. MERIAN expedition MSM76 and recovered during RV POLARSTERN expedition PS131. The attached archive contains raw data files of four Seabird SBE16 SeaCATs (nominal depths: 410m, 472m, 538m, 609m; sampling interval 1h), three SBE56 temperature logger (nominal depths: 442m, 502m, 630m; sampling interval 20s) and two AADI RCM11 current meter (nominal depths: 411m, 610m; sampling interval 2h). Auxiliary information such as sensor calibration sheets, mooring diagrams, and schedule files are also provided, if applicable. The data of one SBE16 (472m) could not be obtained because the instrument did not connect.

Description: Time-series data of ocean current velocities and carbon/particle export were obtained from mooring F4-W-3 in the Fram Strait from June 2021 to July 2022 as part of the Helmholtz infrastructure program Frontiers in Arctic Marine Monitoring (FRAM) and the long-term monitoring program at AWI HAUSGARTEN. The mooring was deployed during RV POLARSTERN expedition PS126, and recovered during PS131. The attached archive contains raw data files of one AADI RCM11 current meter (nominal depth: 143m; sampling interval 1h) and a profiling underwater winch (nominal depth: 114m). The mooring also included one BioOptical Platform (nominal depth: 420m; data archived elsewhere). Auxiliary information such as sensor calibration sheets, mooring diagrams and schedule files are also provided, if applicable. The winch had issues and did not record valid data, but the available files are included here for completeness.