Comparative studies on utilizing nitrogen capacity between two
macroalgae Gracilaria tenuistipitata var. liui ( rhodophyta ) and Ulva pertusa
(chlorophyta) II. Feedback controls of intracellular nitrogen pools on nitrogen
uptake
Affiliations: Aquaculture Research Laboratory, Ocean University of
Qingdao, Qingdao 266003, China. E-mail: liujw@lib.ouqd.edu.cn
Abstract: The potential feedback by intracellular nitrogen pools on maximum N
uptake (NH_4^+) rate were determined for Gracilaria tenuistipitata var. liui
and Ulva pertusa. The results of correlation matrix analyzing showed that the
surge uptake of ammonium seemed related to rapid changes in small intracellular
pools of inorganic nitrogen or small peptide and amino acids rather than to
changes in TN content of the macroalgae. The assimilation rates of nitrogen of
U. pertusa and G. tenuistipitata increased slowly during N starvation and were
mainly regulated by amino acids and some incorporation of amino acids into
macromolecules. From ecological point of view, the fast-growing and uptaking
nutrient U. pertusa is more suitable to improve water quality in integrated
shrimp culture ponds in which external nutrient supplies are usually high and
constant during the culture period, while G. tenuistipitata var. liui is more
suitable to be polycultured in a waters with intermittence supply of
nutrients.