Physiological Impacts of Nitrogen Starvation and Subsequent Recovery on the Red Seaweed Grateloupia turuturu (Halymeniaceae, Rhodophyta)

Grateloupia turuturu is a potential aquaculture species as it has a significant number of high-valued compounds. The purpose of this study was to evaluate the physiobiochemical performances of G. turuturu under nitrogen deficiency and resupply. In this study, G. turuturu was exposed to different lengths of nitrogen starvation (from 0 to 28 days) and subsequently subjected to a 21-day nitrogen-recovery period. The nitrate and ammonium uptake rates, growth rates, and nitrogenous compounds of G. turuturu were periodically measured. The results showed that the nitrogen-starved G. turururu absorbed ammonium much faster than nitrate after nitrogen recovery. Furthermore, an overcompensatory uptake of ammonium was induced via nitrogen deficiency in a short phase after nitrogen resupply. The time and rates of depletion of different compositions varied during nitrogen starvation. Specifically, pigment contents decreased faster than protein and total nitrogen contents, and the reduction rate of protein was the lowest. After nitrogen resupply, though G. turuturu gradually recovered, growth rates and pigments from long-term nitrogen starvations could not recover enough to reach their original values. Our study reveals the physiological changing processes of G. turuturu during nitrogen starvation and recovery and provides baseline information aiding in the development of strategies for G. turuturu cultivation.