Sample collection and sorting

Copepods were collected in Prince William Sound, Alaska in the summer and fall of 2019 during the Northern Gulf of Alaska Long Term Ecological Research (NGA LTER) cruises (https://nga.lternet.edu/). Females “PWS2/June” were collected on June 30th, 2019 at the sampling site PWS2 (Latitude 60° 32.1’N; Longitude 147° 48.2’W) (R/V Sikuliaq, cruise number: SKQ201915S), and the “Pleiades/September” females were collected on September 12th and 13th, 2019 at PWS2 and near the Pleiades Islands (Latitude 60° 16.7’N; Longitude 147° 59.2’W) (M/V Tiglax, cruise number: TGX201909). Copepods were collected with a Midi MultiNet (0.25 m2 mouth area; 150 μm mesh nets) towed vertically from near the bottom to the 163 surface at 0.5 m/sec (PWS2: 798 m; KIP2: 588 m). Upon retrieval, net samples were immediately diluted using filtered seawater collected from depth and kept between 4-6°C to minimize thermal stress. All females selected for the experiments were sorted under a dissecting microscope. Females were placed in groups of three into 750 mL Falcon tissue-culture flasks and incubated under dim light in an incubator for up to 4.5 weeks. Experimental emperatures were at or below deep-water temperatures in Prince William Sound (temperature settings: 4°C for June and 6°C for September). A subset of females was used in the DNA replication experiments; the remaining females were imaged for measurements of prosome length and lipid sac area (see the related dataset https://www.bco-dmo.org/dataset/908514).

Experimental design

For the timeline, sets of females were removed from the incubation flasks for imaging and/or incubations in low concentrations of 5-Ethynyl-2’-deoxyuridine (EdU). Individuals that were imaged as well as incubated in EdU are identified in the dataset and provide identifications used in the related dataset.