不同季节江蓠脱落物对大型海藻场上覆水的影响

Effect of Gracilaria confervoides after falling off on overlying water of seaweed field in different seasons

通过在实验室模拟野外环境,研究了不同季节温度下江蓠(Gracilaria confervoides)腐烂对上覆水溶解氧(DO)和营养盐浓度的影响。根据广东沿海气候特点设计春秋20℃、夏28℃、冬15℃3个对照组,海水平均流速为0.24 m·s-1。结果表明,随着温度升高DO逐渐下降,DO浓度与加入江蓠质量呈负相关关系;江蓠腐烂分解使上覆水总氮(TN)、总磷(TP)浓度先增后减,铵态氮(NH+4-N)与亚硝态氮(NO-2-N)、硝态氮(NO-3-N)浓度同步出现峰值,磷(P)元素的释放早于氮(N)元素;冬季(15℃)和春秋季(20℃)时,NO-2-N和NO-3-N浓度均随江蓠丰度的增加而增大,夏季(28℃)则相反,海藻加入的质量同时影响NH+4-N、NO-2-N、NO-3-N和活性磷(PO3-4-P)的峰值浓度,海藻质量与营养盐浓度呈正相关;低温条件下N、P元素营养盐浓度在上覆水中累积均超过高温条件。研究大型海藻脱落物在不同季节里水解后对上覆水的影响,可为大型海藻增殖密度的确定提供理论依据。

In laboratory simulated environment, we studied the seasonal impacts of the decomposition of Gracilaria confervoides in Daya Bay on the nutrient concentrations and dissolved oxygen in overlying water. According the climate of Guangdong coast, three con- trol groups were designed： spring and autumn in 20 ℃, summer in 28 ℃, winter in 15 ℃, and the average sea water flow rate was 0. 24 m·s-1. The results show that dissolved oxygen （DO） decreased gradually with increasing temperature, and DO was negatively correlated to the biomass of G. confervoides in the water. In the decomposition process of Gracilaria, TN and TP values in overlying wa- ter ascended and then declined; the concentrations of NH4 -N, NO2--N and NO3--N reached the maximum in synchronization. Fur- thermore, the phosphorus released prior to nitrogen. When in winter （ 15 ℃ ） and summer （28 ℃ ）, the concentrations of nitrogen and phosphorus increased with increasing weight of Gracilaria, which was opposite in summer （28 ℃ ）. The peak concentration of pO34--P was also affected by seaweed weight, showing positive correlation, and the accumulation of both nitrogen and phosphorus in o-verlying water in winter （ 15 ℃ ） was obviously higher than that in summer （28 ℃ ）. The results provide references for determining the density of seaweed in proliferation.