崇明北湖叶绿素a浓度与环境因子的GAM回归分析

以崇明北湖为例,采用广义加性模型(GAM)对该湖的叶绿素a浓度与相关环境因子进行分析.结果表明,叶绿素a浓度与总氮、总磷和水温之间存在较好的非线性关系(P<0.05),叶绿素a浓度与总磷之间的关系先为单调递增,当总磷浓度达到0.12mg/L时,变为单调递减;不同总氮浓度区间上,总氮对叶绿素a浓度的影响不同,氮浓度为0.6~1.8mg/L时,对叶绿素a浓度的影响不大;水温在24~26℃时,叶绿素a浓度最高.叶绿素a浓度与氮磷比之间也存在较好的非线性关系(P<0.1),氮限制时,叶绿素浓度与氮磷比呈反比;磷限制时,叶绿素a浓度随着氮磷比单调递减.

Analysis of general additive model on the relationships between chlorophyll-a concentrations and environmental factors in Beihu Lake of Chongming Island

The relationships between chlorophyll-a and its related environmental factors in Beihu lake was studied by GAM method. The total phosphorus, total nitrogen and water temperature were significant as explanatory variables in explaining chlorophyll-a (P<0.05). Chlorophyll-a initially increased monotonically with the total phosphorus, but decreased monotonically after the total phosphorus reached 0.12mg/L. Impacts of different total nitrogen concentrations on chlorophyll-a varied, being weak when the total nitrogen concentration ranged from 0.6 to 1.8mg/L. Highest chlorophyll-a concentrations occurred when the water temperature ranged from 24 to 26℃. Furthermore, the relationship between chlorophyll-a and the TN:TP ratio was significant (P<0.1) nonlinear relationship. Chlorophyll-a was inversely related to TN:TP ratio under nitrogen-limitation. Chlorophyll-a decreased monotonically with TN:TP ratio under phosphorus-limitation.