偏最小二乘回归法在海洋初级生产力影响因子分析中的应用

The Application of Partial Least Squares (PLS) Regression to the Factors Affecting the Ocean Primary Productivity

中文关键词: 偏最小二乘回归法  海洋初级生产力  理化环境因子  富营养化  贫营养化

英文关键词: Partial least squares (PLS) regression  Ocean primary productivity  Physicochemical env¬iron¬ment factors  Eutrophic  Oligotrophic

中文摘要:

      叶绿素a浓度是浮游植物生物量的重要指标，能反映出海洋初级生产力的状况。从海洋监测数据中，分析影响叶绿素a浓度的理化环境因子，尝试找出海洋初级生产力的主导因子。将数据标准化，运用变量投影重要性分析和T²椭圆图等辅助分析技术进行成分提取，进行偏最小二乘回归分析。实验结果表明，在贫营养化的川岛外水域，对叶绿素a影响能力最大的因子为磷酸盐和无机氮，其次为酸碱度、盐度和水温，溶解氧影响能力最小。但在富营养化的沙堤口水域，影响能力最大的因子为化学需氧量和溶解氧，水温也成为影响海洋初级生产力的重要因子，而无机氮却成为非重要因子。从以上结果可见，运用偏最小二乘回归法对叶绿素a影响因子进行探讨，既能在监测数据较少的条件下建立数学模型，又能解决多元回归分析时各理化环境因子之间存在多重相关性的问题，具有较高的相关分析精度。

英文摘要:

      The concentration of chlorophyll-a is an important index of phytoplankton biomass that can reflect the status of ocean primary productivity. According to the analysis on the physicochemical environmental factors that affect the concentration of chlorophyll-a, we may clarify the dominant factors of ocean primary productivity. Two monitoring stations were situated on the sea area in Jiangmen, Guangdong Province, China. The survey was conducted from March to November 2010 to determine chlorophyll-a, water temperature, salinity, pH, dissolved oxygen (DO), chemical oxygen demand (COD), phosphate, nutrient N and oil in two stations. According to the principal component analysis (PCA), the application of the partial least squares (PLS) regression solved the multiple regression analysis including the multiple correlations between the environmental factors with a high precision; it also established the mathematical model with fewer monitoring data. In the PLS regression, the monitoring data were normalized, and then used the variable importance in projection and T² ellipse fitting-aided analysis technique for extraction. The regression equation of station A was y = 0.0076x₁-0.0806x₂-1.2869x₃+ 0.1498x₄-0.1905x₅ 126.6x₆ 5.985x₇-0.3538x₈ 10.84. The regression equation of station B was y= 0.0781x₁ 0.5852x₂ 0.4773x₃-0.5661x₄-38.11x₅ 0.8501x₆-4.429. The eutrophic index of station A was 0.041, suggesting that the water of Chuandao sea area was oligotrophic. The eutrophic index of station B was 1.005, suggesting that the water of Shadi sea area was eutrophic. The results showed that the main effective factors of chlorophyll-a were nutrients N and phosphate in oligotrophic waters of Chuandao sea area, and that COD, DO and water temperature were the effective factors of the ocean primary produ¬ctivity in Shadi sea area.