铜藻(Sargassum horneri)在营养限制胁迫后对NH_4-N的超补偿吸收研究

NH4-N OVER-COMPENSATORY UPTAKE OF SARGASSUM HORNERI UNDER THE STRESS OF NUTRIENTS DEFICIENCY

以经济马尾藻铜藻(Sargassum horneri)为研究材料,研究了其在营养限制胁迫后对NH_4-N的超补偿吸收情况。实验分营养限制和恢复营养两个阶段进行,每个阶段均设置饥饿处理组、饱和处理组和正常对照组。铜藻在低营养限制胁迫(饥饿)下培养10天后,恢复营养盐培养3天,分别采用次溴酸盐氧化法和锌镉还原法测定培养液中的NH_4-N和NO_3-N的浓度。本文研究发现,饥饿处理组中铜藻吸收氨氮的速率远高于正常对照组和饱和处理组,在恢复培养第一天时,饥饿处理组对NH_4-N的吸收速率最高为14.94μmol/(g·h),与正常对照组及饱和处理组间差异显著。在恢复培养的后两天,三个处理组中铜藻对NH_4-N的吸收速率差异慢慢变小,直至最后几乎相同。三组对NO_3-N没有表现出较高的吸收,最高仅为6.15μmol/(g·h),结果表明:氮源包括NH_4-N和NO_3-N时,铜藻优先选择吸收NH_4-N。实验后称重测定生长速率:对照组、饥饿处理组和饱和组生长率(SGR)分别为8.48%、8.86%、8.01%,ANOVA方差分析表明,三者存在显著差异(P=0.032<0.05),从而证实了铜藻也存在超补偿生长的现象。

In this paper, Sargassum horneri was used as experimental material for the study of NH4-N over-compensatory uptake under laboratory conditions. Sargassum horneri was thoroughly cleaned, epibiotics carefully removed, and cultured in beakers in an illuminating incubator under 15℃, 100-mol/（m2.s）, L：D 12h/12h, 30 salinity and pH 7.5--8.0. The experiments included two periods. Firstly, Sargassum horneri was cultured for 10 days under the condition of nutrients stress, i.e. nutrients deficiency and nutrients enrichment, with fresh sea water one as the control. Secondly, the nutrients stress was lifted; the treated and the control were simultaneously cultured for another 3 days under the same nutrients supply with daily medium change. The experiments were carried out in 2L beakers with 3g Sargassum horneri and 1L medium, and the concentration of NHa-N and NO3-N was 100 and 280-tmol/L respectively. Triplicate were set for each group. During the experiment, the NH4-N, NO3-N uptake rate were measured periodically. After subjecting to the nutrients deficiency, Sargassum horneri showed a strong ability of NH4-N uptake. The uptake rate of NH4-N of the starved group, the control group and the fed group, was 14.94, 11.54, and 9.63gmol/（g.h）, respectively. The starved had the highest uptake rate of NH4-N but its highest uptake rate of NO3-N was only 6.15gmol/（g.h）, much smaller than that of NH4-N, indicating that Sargassum horneri assimilated NH4-N first. As a result, the concentration of NO3-N in the beakers was 3 times higher of the NH4-N. As the culture time proceeded, difference between the treated and the control decreased gradually and finally were equivalent. The special growth rate （SGR） in the group of the starved, the control and the fed was 8.86%, 8.48%, and 8.01% respectively. The difference of the growth rate between the treated and the control was significant （P = 0.032〈0.05）. After 10 days of nutrients deficiency, there was a short phase of rapid NH4-N uptake demonstrating over-compensatory growth. Thus, NHa-N over-compensatory uptake of Sargassum horneri could be used as a guidance for cultivation. Moreover, Sargassum horneri have very high productivity and ability of absorbing large quantities of N. It is believed that Sargassum horneri cultivation in large-scale is a ~ood solution to eutronhication in coastal waters.