Dataset: Egg production rate (EPR) and egg hatching success (HS) data for Acartia tonsa during multigenerational exposure to ocean warming (OW), ocean acidification (OA), and combined ocean warming and acidification (OWA)

Three hundred copepods were collected in April of 2018 from eastern Long Island Sound, Connecticut, USA (41.3°N, 72.0°W) and raised for one year (~12 generations) (14 degrees Celsius (°C), 400 microatmospheres (μatm) CO2, 30 ‰ salinity, 12:12 hours light:dark) as stock cultures to limit maternal effects (Falconer, 1989, Introduction to Quantitative Genetics). Three resulting stock cultures with >2,000 individuals each were combined and then split evenly into three groups for each of the four treatments. Groups were acclimatized within a generation to temperature (15°C or 13°C, 1°C per day) and pCO2 (1000 μatm, 100 μatm per day, OA treatments only). Groups seeded the F0 individuals for 7-10 days yielding ~15,000 eggs per treatment. Resulting F0 eggs and nauplii were combined for each treatment, redistributed among three replicate cultures, and returned to their respective experimental conditions. The experimental environmental conditions were: 1) Ambient control (AM): 13°C, 400 µatm CO2, pH = 8.2; 2) Ocean Acidification (OA): 13°C, 1000 µatm CO2, pH = 7.85; 3) Ocean Warming (OW): 15°C, 400 μatm CO2, pH = 8.2; 4) Combined warming and acidification (OWA): 15°C, 1000 μatm CO2, pH = 7.85. Copepods were fed equal proportions of the live phytoplankters Tetraselmis sp., Rhodomonas sp., and Thalassiosira weissflogii every 48-72 hours to achieve food-replete conditions (≥600 micrograms (μg) Carbon per liter (L)) (Feinberg and Dam, 1998. Marine Ecology Progress Series), deliberately raised under ambient conditions to avoid confounding effects of possible food quality changes.

For each replicate culture within a treatment, 12 pairs of newly developed adult males and females were placed into 25 milliliter (mL) Petri dishes housed in the plexiglass enclosure described above for 96 hours (N= 108 per treatment for F0 to F4). Adults were transferred to a new dish after 48 hours. For food limitation experiments in F11, the 12 pairs were split equally among the three food concentrations. Adults in food limitation experiments laid eggs for 72 hours and were transferred to a new dish daily to maintain food concentration during the experiment. After the egg-laying period, adults were checked for survival and removed from the Petri dishes. Eggs were left in the dishes for an additional 72 hours to hatch and then preserved with non-acid Lugol’s solution. Dishes with dead males were used for EPR, but not HS, since fertilization could not be assumed. Dishes with dead females were discarded. We independently evaluated survival in additional assays, thus the measurements for this assay were only used to estimate the number of offspring produced for live copepods. EPR was calculated as the number of eggs produced per female per day and HS was calculated as the proportion of live nauplii from produced eggs.