基于GAM模型的太湖叶绿素a含量与环境因子相关性分析

随着富营养化程度的加剧，太湖近30年来水华频发.为了探讨太湖西部沿岸水华暴发与环境因子的关系，于2017年4月1-18日（当地历年蓝藻暴发早期）在太湖西部沿岸进行了密集原位调查.共采集样品72个，测定了水温、溶解氧、各形态氮、磷营养盐浓度以及风速等环境指标，并利用GAM（广义相加模型）定量分析了叶绿素a含量与各环境因子间的关系.结果表明:①叶绿素a含量波动幅度较大（17.10~795.89 mg/m3），太湖西部沿岸带有明显的蓝藻水华暴发现象.②水温、风速以及硝态氮浓度与叶绿素a含量的变化显著相关（P<0.05），各环境因子按其对叶绿素a含量变化的解释率排序为水温>风速>硝态氮浓度.其中水温是影响叶绿素a含量最为重要的环境因子，叶绿素a含量随着水温的升高呈现明显上升趋势.风速也是影响叶绿素a含量的关键因子之一，较低的风速（<3 m/s）有利于蓝藻的漂移集聚从而形成水华，引起叶绿素a含量的升高.研究显示，GAM模型较好地解释了叶绿素a的含量变化，模型总体解释度达到70.6%，可为太湖西部沿岸蓝藻水华早期的预测预警提供一定的基础支撑. 

Relationship of Chlorophyll-a Content and Environmental Factors in Lake Taihu based on GAM Model

Lake Taihu has become increasingly eutrophic over the past three decades and the algal blooms occurred frequently. To explore the relationships between environmental factors and algal blooms in the west littoral zone of Lake Taihu, an investigation was conducted at one sampling site located in the west littoral zone of Lake Taihu (where algal blooms always happened) from April 1^st to 18^th, 2017. A total of 72 samples were collected, and environmental factors including wind speed, water temperature, dissolved oxygen and nutrient concentrations were measured. Generalized additive models (GAM) were applied to reveal the quantitative relationships between chlorophyll-a content and environmental factors. The results showed that serious algal blooms happened and the chlorophyll-a content fluctuated dramatically (17.10-795.89 mg/m³). Among the environmental factors, water temperature, wind speed and nitrate had good correlations with chlorophyll-a content (P<0.05). The orders of the contribution to chlorophyll-a content variation were in sequence of water temperature, wind speed and nitrate. Water temperature is an important environmental factor influencing chlorophyll-a content that increased with water temperature. Wind speed was one of the key factors which influenced chlorophyll-a content, low wind speed (< 3 m/s) promotes algae breeding and make the algae gather, these led to the algae blooms and high content of chlorophyll-a.GAM explained for 70.6% of the chlorophyll-a content variation, to some degree, the research can be used for prediction and forewarning of algal blooms in west littoral zone of Lake Taihu.