2). Plots of laboratory versus NIRS-predicted content values (Fig. 2) for each constituent show tight linear relationships with high correlation values (Table 2). Effects of temperature and nitrogen availability on tissue qualities.  The development of new tissue was observed under all experimental conditions during the 8 d experiment. The addition of NH4+ had a significant positive effect on growth (F3,24 = 7.78, P < 0.001; Fig. 3)

at both 21°C and 28°C. The addition of nitrogen had a significant effect on the total phlorotannin content in S. flavicans (Table 3; Fig. 4, a and b). Tissue grown under the highest concentration of NH4+ (28.5 μM) had significantly lower phlorotannin content than tissue grown under lower NH4+ (<0.5 and 7.1 μM) concentrations. There was a significant three-way interaction between NH4+, temperature, Selleckchem PLX4032 Ferroptosis inhibitor and age (Table 3; Fig. 4, a and b). New tissue grown at 21°C under ambient NH4+ (<0.5 μM) conditions had significantly lower phlorotannin concentrations than new tissue grown under ambient NH4+ at 28°C (Fisher’s LSD post hoc test; Fig. 4, a and b). Sargassum tissue grown under the highest concentration of NH4+ (28.5 μM) had significantly higher total nitrogen content than tissue grown under the lower NH4+ concentrations of <0.5 and 7.1 μM (Table 3; Fig. 4, c and d). Older tissue

had significantly higher total N content than new tissue (Table 3; Fig. 4, c and d),

and tissue grown at 21°C had higher total N than tissue grown at 28°C (Table 3; Fig. 4, c and d). The carbon content of Sargassum tissue deceased when grown under increased NH4+ concentrations (Table 3; Fig. 4, e and f), and new tissue had significantly higher carbon content than old tissue (Table 3; Fig. 4, e and f). The C:N ratio of Sargassum tissue grown at 28°C was significantly higher than tissue grown at 21°C (Table 3; Fig. 4, g and h). New tissue had significantly higher C:N ratio than old tissue (Table 3; Fig. 4, g and h), and the C:N ratio of tissue decreased with increased NH4+ concentrations (Table 3; Fig. 4, g and h). The C:N ratio of tissue grown under the highest NH4+ concentration (28.5 μM) was significantly lower than in all other treatments, and tissue grown under selleck compound the intermediate NH4+ concentration of 14.2 μM was significantly lower than tissue grown under ambient (<0.5 μM) NH4+ concentrations (Fig. 4, g and h). We have shown that NIRS can be used to accurately predict traits of algal tissue (nitrogen, carbon, and phlorotannin as phloroglucinol equivalents) that are fundamental for studies of physiology, ecology, and algal-herbivore interactions. We demonstrate the utility of NIRS as a time-efficient alternative to conventional methods of algal tissue analysis, which facilitates the evaluation of microscale variation in algal traits, due to the reduced amount of tissue required for analysis.