Growth rate and carrying capacity of Antarctic phytoplankton in response to temperature and nitrogen:phosphorus supply interactions

Data were obtained from a laboratory growth experiment conducted from April to Mai 2021 at the Institute for Chemistry and Biology of the Marine Environment (University of Oldenburg). Three Antarctic phytoplankton species (Chaetoceros simplex, Phaeocystis antarctica (single cell culture) and Geminigera cryophila) were grown in monocultures and a mixture of all three species. We used a factorial design including four different N/P treatments (control plus three different N/P levels) and 10 different temperatures (-2, -1, 0, 1, 2, 3, 4, 6, 8 and 10°C). The detailed experimental setup is explained in doi:10.1594/PANGAEA.971329. Potential maximum biomass (carrying capacity, K) and the maximum growth rate (µmax) of the monocultures and the mixed assemblage were calculated by using the optical density measurements (OD 440nm) and the logistic growth curve formula: OD=(KN_0 ⅇ^(μmaxt))/((K+N_0 ) ⅇ^(μmaxt⁻¹) ) where OD is the optical density, t (time) is the experimental day, N0 the lowest optical density (start value), K the carrying capacity and µmax the maximum growth rate. Starting parameters were estimated individually for each experimental unit. Optical density (OD₄₄₀) was measured every second day using a microplate reader (Biotek, USA). The final sampling of each culture was conducted during stationary phase, when the OD value was stable during three consecutive sampling days. The stationary phase was reached between 30 and 48 days, depending on the temperature and nutrient treatment.