Summary of sea-ice conditions and types of data collected at each site (denoted by <i>x</i>).

Site codes are used in Fig 1. Ice-rank is an ordinal number given to sites where biota were sampled, based on light measurements and long-term visual observations (NA refers sites where biota were not sampled). Lower numbers indicate later sea-ice breakout. Ice-zone is a classification is given to all sites, for categorical analyses and to describe unranked sites.