Dataset: Particulate nutrients for G. huxleyi RCC874 and RCC914 N amendment laboratory-based culture experiment

G. huxleyi strains RCC874 and RCC914 were obtained from the Roscoff Culture Collection (RCC). The cultures were transferred from the maintenance stock into artificial seawater (40 g Instant Ocean® Sea Salt per L Milli-Q® water) amended with nutrients, trace metals, and vitamins according to the L1 recipe (https://ncma.bigelow.org/algae-media-recipes) without silica (herein reported as L1-Si). The temperatures were selected to simulate no heat stress (18°C), moderate heat stress (22°C), and high heat stress conditions (25°C and 28°C for RCC874 and RCC914, respectively). The cultures were acclimated to the temperature conditions under a 14:10 light/dark cycle for approximately 10 days prior to the start of the experiment.

Following acclimation, cultures were transferred in triplicate into 2.8 L Fernbach flasks at an initial concentration of 1.0 ✕ 10⁵ cells mL⁻¹. The cultures were divided into two conditions: nitrogen-replete (N replete; L1-Si with standard 8.82 ✕ 10⁻⁴ M NaNO₃) and nitrogen-limited (N limited; L1-Si with 8.82 ✕ 10⁻⁵ M NaNO₃). When N-limited cell counts significantly deviated from the N-replete condition, between 7–9 days after inoculation, the cultures were sampled for particulate nutrients. Samples for particulate nutrient composition were filtered onto muffled 0.7-µm Whatman GF/F filters using gentle vacuum pressure, sampling 25–100 mL of culture depending on cell density. Samples were processed for particulate carbon (PC), particulate nitrogen (PN), and particulate phosphorus (PP) at the University of Maryland Center for Environmental Science Chesapeake Biological Laboratory Nutrient Analytical Services Laboratory.