Scanning electron micrographs of Central Arctic Ocean prokaryotes from the Synoptic Arctic Survey 2021

Electron microscopy images show different shapes and morphologies of Central Arctic Ocean prokaryotes collected during the Synoptic Arctic Survey 2021. The seawater samples were pre-filtered through 1.2 µm, 142 mm ø polycarbonate filters (Isopore, Merck Millipore) and subsequently 100× concentrated onto polycarbonate track-etched filters with 0.2 µm pore size and 47 mm ø (Sartorius) to enrich the prokaryotic fraction. The concentrated samples were fixed using glutaraldehyde and phosphate buffer (pH 7.2) and stored at -20 °C. The fixed samples were examined by scanning electron microscopy (SEM) using a Carl Zeiss Merlin FE-SEM operated at 5 kV and 150 pA. Samples were collected from five different stations and sea-basins: station 5 (Nansen Basin); stations 26 and 42 (Makarov Basin); and stations 53 and 56 (Amundsen Basin). Four different depths were sampled in duplicate at each station: 10m, chlorophyll-a maximum depth (20-45m), temperature-maximum depth (274-354m), and 500m. The sample ID for each image is structured as follows: SO21-St.x-SEFxi.ni_di. Here, SO21 denotes Synoptic Arctic Survey 2021; St.x represents the respective station; SEFxi.ni indicates scanning electron microscopy after filtration (1.2 µm), where xi represents the running number of samples collected onboard and ni denotes the number of images captured from that sample; di denotes the depth in meters from which seawater was collected. Associated spreadsheet file contains two worksheets: cellshape_counts, and morphological_features_counts, showing the different cell shapes and morphological features observed. The results will be published in a scientific article entitled “Low prokaryotic growth efficiency inflates carbon demand in the Central Arctic Ocean.”