东楮岛海草组织碳氮含量特征及环境影响因素

Carbon and Nitrogen Content Characteristics in Seagrass Tissues and Environmental Effects in Dongchu Island

海草组织碳氮含量可快速响应外界环境影响,已经广泛用于海草生态系统健康评估的指示因子。2011—2012年对东楮岛大叶藻海草床进行4次采样调查,研究了不同季节海草组织碳氮含量特征,分析了环境因素对大叶藻组织碳氮含量的影响。结果表明:海草组织碳、氮含量有明显季节性变化。海草叶碳含量最大值出现在5月,为36.4%,最小值出现在12月,为30.8%;而海草叶氮含量最大值和最小值分别出现在2和5月,为2.73%和2.02%。环境因素的相关性分析表明,海水温度对海草叶碳含量和根氮含量具有显著影响,海水及沉积物间隙水中的氮营养盐对海草茎、叶中的碳含量和根、叶中的氮含量有显著影响。调查表明东楮岛海域海草组织氮含量高于世界平均水平,营养盐增加可能对大叶藻产生负面影响,为了保护东楮岛海草床,应严格控制该海域养殖海带过程中营养盐的使用,加强对海草床健康状况的野外监测以及环境因素对海草影响的室内模拟实验研究。

Seagrasses provide important ecosystem service.In recent years,seagrasses degradation has been reported mainly due to seawater eutrophication and sea reclamation.Carbon（C）and nitrogen（N）content of seagrasses tissues（leaves,rhizomes and roots）can fast indicate seagrasses response to environmental variables,which has been widely used to evaluate seagrass bed healthy status.Seagrasses,seawater,porewater in the sediment samples were collected in four seasons in seagrass beds in Dongchu island,Weihai,Shandong Province during August 2011 to May 2012.Our results showed that C and N content of seagrass tissues obviously changed in four seasons.The maximum C content value in the leaves was36.4%in May and the minimum was 30.8%in December.Meanwhile,the highest（2.73%）and lowest（2.02%）N content value of seagrass leaves separately appeared in February and May.Seawater temperature had significant effects on C content of seagrass leaves.There were significant correlations between inorganic nitrogen,ammonium and nitrate in seawater,porewater of the sediment and C content of seagrass leaves and rhizomes.Salinity was positively correlated with the seagrass leaves C content.N content of seagrass roots was significantly affected by seawater temperature.There were significant correlations between inorganic nitrogen,ammonium and nitrate in seawater,sediment porewater and N content of seagrass roots.There were significant correlations between nitrate in seawater,inorganic nitrogen,ammonium and nitrate in sediment porewater and N content of seagrass leaves.There were significantly negative correlations between ammonium,nitrate in seawater,inorganic nitrogen,ammonium and nitrate in sediment porewater and C/N ratio content of seagrass leaves.The nutrients in seawater and sediment porewater had little effect on seagrass tissues C content directly,but can impact N content of seagrass tissues.Furthermore,the N absorption of seagrass tissues can use C of seagrass tissues during seagrass metabolic processes.Consequently,nutrient over-enrichment has effects on C content and C/N ratio of seagrass tissues.In order to protect the seagrass beds in this area,the use of nutrient in the process of Luminaria japonicaaquaculture should be strictly controlled.In addition,seagrass bed monitoring and mesocosm experiments about the effects of environmental factors on seagrasses should be strengthened.In the conditions of seagrass beds degradation in China,our study could provide basic data for the seagrass ecosystem health evaluation and the restoration of degraded seagrass ecosystems.