Effect of different nutrient salts on growth and chemical constituents of Gracilaria blodgettii

In order to determine the best ecological conditions for the growth of Gracilaria blodgettii, we observed the changes in its relative growth rate (RGR) and biochemical constituentsat different total inorganic nitrogen concentrations (48 molL-1，96 molL-1，144 molL-1，192 molL-1，240 molL-1，288 molL-1，336 molL-1) and with different N/P values (1/1，5/1，10/1，50/1，100/1). The optimum total inorganic nitrogen concentration was 192 molL-1; the optimum N/P value was 10/1；the optimumm(NO3--N):m(NH4+-N):m(NO2--N) were 1:10:5 and 5:10:1. Under these conditions, G.blodgettii obtained higher RGR, the highest contents of phycobiliprotein and soluble protein, but lower peroxidas (POD) activity and malondialdehyde (MDA) content. However, the algae suffered malnutrition and slow growth when total inorganic nitrogen concentration was too low, N/P value was too high and the ratio of NH4+-N to total inorganic nitrogen was relatively low.