淡水湖泊营养状态监测新方法--叶绿素比值模型

A new trophic status monitoring method for freshwater lakesthe chlorophyll ratio model

选取铜绿微囊藻、鱼腥藻、蛋白核小球藻、汉氏菱形藻、薄甲藻和小定鞭金藻作为湖泊水体从富营养状态到贫营养状态的代表藻种,用热乙醇-反复冻融-分光光度法测定其叶绿素a、b、c的浓度,通过分析叶绿素(chl)的比值、藻类种群组成和水体营养水平之间的响应关系,建立了叶绿素比值模型作为评价水体营养状态的一种新方法.在计算单种藻类chlb/chla、chlc/chla比值的基础上,结合目前我国湖泊水体不同营养水平藻类种群组成的统计数据,得到不同营养状态下多种藻类同时存在时水体chlb/chla和chlc/chla比值的变化曲线.结果表明,在中营养和贫营养水体中,chlc/chla值随营养水平的降低呈明显单调上升的趋势;在富营养化水体中,chlb/chla值随营养水平的降低而呈明显单调上升的趋势.根据这个规律,提出了判断水体营养水平的新标准,即:当chlc/chla>0.30时,水体为贫营养;当0.18<chlc/chla<0.30时,水体为中营养;当chlc/chla<0.18时,水体为富营养,此时,需要借助chlb/chla的值进行进一步的判断:当chlb/chla>0.14时,水体为轻度富营养化;当0.08<chlb/chla<0.14时,水体为中度富营养化;当chlb/chla<0.08时,水体为重度富营养化.以白洋淀为研究案例,分析结果表明,叶绿素比值模型判断和综合营养状态指数法判断结果相符.因此,叶绿素比值模型可以作为简单、快捷、准确的评价我国淡水湖泊营养状态的方法.

The ratios of chlorophyll （chl） b/a and c/a in algae,including Microcystis aeruginosa,Anabaena sp.,Chlorella pyrenoidosa,Nitzschia hantzschiana,Glenodinium pulvisculus and Prymnesium parvum,were measured through spectrophotometry.The ratios of chl b/chl a and chl c/chl a of mixed algae in waters with different trophic status were calculated according to the different algae population compositions.The relationship between these ratios and the water trophic status were analyzed.The results showed that when the water status changes from hyper eutrophic to mid-eutrophic,the ratios of chlorophyll b/a showed a steep increase;while when the water status changes from light-eutrophic to oligo-trophic,the ratios of chlorophyll c/a steeply increased.Consequently,it is possible to classify the water trophic status quickly and accurately by chlorophyll ratios model as follows.When chl c/chl a〉0.30,the water trophic status is oligo-trophic;when 0.18 〈chl c/chl a〈0.30,the water trophic status is mesotrophic;when chl c/chl a〈0.18,chl b/chl a〉0.14,the water trophic status is light-eutrophic;when chl c/chl a〈0.18,0.08〈chl b/chl a〈0.14,the water trophic status is mid-eutrophic;when chl c/chl a〈0.18,chl b/chl a〈0.08,the water trophic status is hyper-trophic.Forty-five water samples were collected from Baiyangdian Lake and were analysed by both the chlorophyll ratio model and the Trophic Level Index （TLI） to determine the lake＇s trophic status in April,June,July,August and October,2007.The results of the two methods were consistent with each other.Compared to the TLI,the chlorophyll ratio model is a simple and rapid method which can be used to determine the trophic status of freshwater lakes in China.