太湖叶绿素a年际变化的主要驱动因子及未来气候的影响

Main factors driving inter-annual variability of chlorophyll-a and the influence of future climate on chlorophyll-a in Lake Taihu

根据1985—2011年的大气与湖泊观测数据以及CNRM-CM5模式模拟的RCP4.5情景下太湖未来气温变化数据,采用偏最小二乘回归分析及预测方法,分析了年际尺度上气温、水体总氮(TN)、总磷(TP)、无机磷(IP)和溶解的硅元素(Si)等因子对太湖叶绿素a(Chl-a)浓度变化的影响,并进一步评估了未来气温变化对Chl-a浓度的影响。结果表明:1980—2011年,太湖年平均气温呈显著的增暖趋势,增温速率约为0.73℃·10 a-1;在1985—2011年,Chl-a浓度也表现出显著的增加趋势,年增加速率达到0.43μg·L-1;TN和Si的增加趋势较为显著,而TP和IP的增加趋势不十分显著;相关分析及偏最小二乘回归分析均说明,相对于营养物质,气温在调控太湖Chl-a的年际变化过程中发挥着主导作用,而就营养物质而言,TN和Si对年平均Chl-a浓度年际变化的调控作用大于TP和IP;在RCP4.5情景下,太湖未来气温将以0.19℃·10 a-1的速率增加;当前营养物浓度条件下,太湖浮游植物生物量也将显著增加,Chl-a浓度10年滑动平均值最高达到34.18μg·L-1,发生在2075—2085年;在将TN浓度消减1/2情况下,未来Chl-a浓度的10年滑动平均值最高为28.91μg·L-1,也出现在2075—2085年,小于当前营养物质浓度条件下的最小Chla浓度值,可以有效缓解未来气候变暖对太湖富营养化的影响。

Based on observation data of atmosphere and Lake Taihu from 1985 to 2011 and the air temperature data （RCP4.5） of the model CNRM-CM5 output, partial leastsquares regression （PLSR） was used to analyze the annual relationships between chlorophyll-a （Chl-a） and air temperature, total nitrogen （TN）, total phosphorus （TP）, inorganic phosphorus （IP）, dissolved silicon （Si）, and to forecast the effect of future climate warming on Chl-a. The results showed that from 1980 to 2011, annual mean air temperature in Lake Taihu had been increasing at a rate of about 0.73 ℃·10 a-1. Chl-a concentration also appeared an increasing trend at about 0.43 μg·L-1 per year from 1985 to 2011. For nutrients, TN and Si had a more significantly increased trend than TP and IP. Relative to nutrients, air temperature was a dominant factor controlling the annual variation of Chl-a concentration according to the correlation analysis and PLSR. Furthermore, the variability of Chl-a concentration more depended on TN and Si than TP and IP. Under RCP4.5 Scenario, the future annual mean air temperature would increase at a rate of 0.19 ℃·10 a-1 in Lake Taihu. Under current nutrient conditions, the phytoplankton biomass （Chl-a concentration） would also have a significantly increasing tendency. According to the 10-year running average value of Chl-a concentration, the increasing tendency would reach the peak value （34.18 μg·L^-1） during 2075-2085. If reducing the TN concentration to half of the present value, the peak value of Chl-a would be 28.91 μg·L^-1 during 2075-2085 and would be less than the minimum value of Chl-a concentration in the current conditions, which could mitigate the effect of climate warming on eutrophication.