Experimental design for studying nitrogen uptake in Heterosigma akashiwo under varying nitrogen sources and labeled nitrogen spikes.
Diagram showing an experiment with Heterosigma akashiwo culture under different ambient nitrogen sources (100% NO₃⁻, 50% NO₃⁻/50% NH₄⁺, 100% NH₄⁺), followed by 4 replicate subcultures and nitrogen spike treatments using ¹⁵N-NH₄⁺, ¹⁵N-NO₃⁻, and ¹⁵N-NO, with a control group.