Winter microalgal communities of the southern Sea of Okhotsk: A comparison of sea ice, coastal, and basinal seawater

•The winter microalgal communities were investigated using both microscopy and DNA barcoding.•Diatoms dominated the winter microalgal communities in both sea ice and seawater.•Sea ice algae were much more abundant than phytoplankton.•The composition of the phytoplanktonic communities was dependent almost entirely on whether they were within the influence of the ESC.