程海冬季水华暴发期间氮、磷营养元素的形态与分布

氮、磷营养元素是湖泊生态系统中极其重要的生态因子,它们以不同形态存在于湖泊水体中,表现出不同的地球化学行为和生态效应,从而支配着湖泊生态系统的生产力水平和湖泊富营养化进程。通过设置3个断面9个采样站14个采样点,研究了程海湖水体中氮、磷营养元素的形态与分布,结果表明：2009年11月23日—2010年2月20日,以铜绿微囊藻（Microcystis aeruginosa Kutz.）为主的程海冬季水华暴发期间,总氮质量浓度0.540~3.906 mg.L-1,平均0.836 mg.L-1;总磷质量浓度0.036~0.166 mg.L-1,平均0.061 mg.L-1。其中,溶解态氮、溶解态磷分别为61.7%和50.8%。溶解态氮以有机氮为主,溶解态磷则以无机磷为主。水华期间生物可直接利用氮质量浓度0.118 mg.L-1;生物可直接利用磷质量浓度0.021 mg.L-1,分别占总氮、总磷质量浓度的14.1%和34.4%,显示出此特定时期,氮的消耗速度较磷快。氮素、磷素及其赋存形态在程海的时间分布上有不同的节奏;水平分布差异不明显;垂直分布在水表层至亚底层的水柱中差异也不明显,而在湖底层最高。

The N and P chemical speciation and temporal-spatial pattern during a winter bloom event in Lake Chenghai,China

Nitrogen（N） and Phosphorous（P） are important ecological factors in lake ecosystems.In lake waters,these key nutrients can exist in various chemical forms that demonstrate distinct geochemical behaviors,imposing significant ecological effects on the primary productivity and eutrophication process in lakes.This paper presents the trend and pattern of N and P distribution in Lake Chenghai during a winter bloom event based on monitoring data sampled at three cross-sections and nine stations.The winter bloom was observed to have occurred from November 23th,2009 through February 20th,2010,where the dominant algal species was Microcystis aeruginosa.Data collected through this period show that the water column total nitrogen（TN） concentrations ranged from 0.540 to 3.906 mg·L-1,with a mean of 0.836 mg·L-1;the total phosphorous（TP） concentrations ranged from 0.036 to 0.166 mg·L-1,with a mean of 0.061 mg·L-1.Both N and P are primarily in dissolved form,accounting for 61.7% and 50.8% of the TN and TP,respectively.A further analysis suggests that majority of the dissolved TN are in organic form,while the dissolved TP is mainly composed of inorganic form.The bio-available concentration was 0.118 mg·L-1 for N and 0.021 mg·L-1 for P,representing respectively 14.1% and 34.4% of the TN and TP,suggesting a faster uptake of N than P by phytoplankton during the bloom.The N and P in the lake demonstrate different temporal pattern while showing insignificant variability across the horizontal domain.The most striking vertical distribution pattern is that there is only slight difference between TN and TP at shallow to intermediately deep water,but at the bottom of the water both nutrients reached significantly higher concentrations than at other depths.