洞庭湖生源要素分布特征及生态效应

Distributions Characteristics of Nutrients and Corresponding Ecological Effects in Dongting Lake

根据洞庭湖城陵矶站1990—2015年月平均COD,TN和TP浓度的监测资料,基于趋势分析方法,系统地研究洞庭湖水体生源要素的年内变化和年际变化规律,进一步揭示其化学计量比例特征,在此基础上探讨生源要素浓度及结构对藻类生长的影响。结果表明,多年平均COD,TN和TP浓度的年内变化规律相似,均表现为非汛期>汛期;多年变化趋势方面,1990年以来,洞庭湖城陵矶站年平均COD,TN和TP浓度均呈现显著的上升趋势,对应C:N和C:P随时间推移而下降,N:P则表现为上升。洞庭湖城陵矶站水体C:N:P平均为13:18:1,冗余分析结果表明水体生源要素浓度及化学计量比会影响藻类生长,其中C:N,C:P和COD起主导作用。研究时段内城陵矶站水体氮磷含量整体偏高,已满足藻类生长需求,为避免水华爆发等不良生态后果,应控制外来氮磷输入,保持湖体化学计量比的平衡。

Based on monitoring data of monthly average COD,TN,and TP concentrations at Chenglingji hydrological station in Dongting Lake from 1990 to 2015,the intra-annual variation,inter-annual variation patterns of nutrients in the water column of Dongting Lake were systematically studied by trend analysis,and further revealed their stoichiometric ratio characteristics and discussed the effects of nutrient concentrations and structure on algal growth.The findings showed that the intra-annual variation patterns of average COD,TN,and TP were similar,indicating that the nutrient content in dry season was higher than that in wet season.However,as for multi-year trend,the annual average COD,TN,and TP in Dongting Lake showed a significant increase since 1990,while C:N and C:P ratios decreased and N:P ratio increased over time.The average C:N:P ratio in the water column of Chenglingji station in Dongting Lake was 13:18:1,and redundancy analysis showed that nutrient concentrations and stoichiometry ratios in the water would affect algae growth,with C:N,C:P and COD playing a dominant role.During the study period,the overall nitrogen and phosphorus content of the water column in Chenglingji station was generally high and has already met the algae growth demand.In order to avoid adverse ecological consequences such as harmful algal bloom events,external nitrogen and phosphorus inputs should be controlled to maintain the stoichiometric ratio balance in the water column of Dongting Lake.