光照与通气方式对蓝、绿藻竞争生长和磷的水-沉积物界面过程的影响

室内模拟研究了太湖普遍存在的浮游藻类蓝藻(铜绿微囊藻)和绿藻(四尾栅藻)在不同光照和通气条件下的生长过程,以及该过程对水体理化性质以及水-沉积物界面磷交换过程的影响.研究结果表明,实验条件下(光照:2500lx;温度:27℃),蓝藻(铜绿微囊藻)具有绝对的竞争优势,成为水体中优势藻类.铜绿微囊藻在通空气和通氮气条件下均可以生长繁殖,在通氮气条件下需要较长时间的适应期,但达到的最大生物量远高于通空气条件.实验过程中,上覆水可溶性无机磷(DIP)浓度的变化为:无光环境＞有光环境,通氮气环境＞通空气环境,这种变化与有无藻类生长过程密切有关.有光条件下,藻类生长对磷的需求刺激了沉积物中生物可利用磷(AAP)的释放,同时也刺激了沉积物各种不同形态磷之间的相互转化.通氮气条件下,沉积物中磷的释放以Fe-P为主,Ca-P含量有所提高;通空气条件,Fe-P含量变化不大,Ca-P在有光组略有下降,但无光组变化不大;各试验组中有机磷和残渣磷的变化量基本相同;各试验组TP含量的变化不大.

Effects of light and aeration on competition between Microcystis aeruginosa and Scenedesmus quadricauda and phosphorus release at the water-sediment interface

Competition between Microcystis aeruginosa and Scenedesmus quadricauda and phosphorus release at the water-sediment interface were studied in laboratory simulation experiments where lighting and aeration were varied. The results showed that Microcystis aeruginosa was dominant in both aerobic and anoxic experimental conditions. The sequence of phosphorus concentration in overlying water was: no light irradiation > light irradiation, anoxic condition > aerobic condition, and the changes were related to algal growth. The bioactivity of algae and microorganisms was increased under light irradiation, which stimulated the release of bio-available phosphorus from sediments. So the quantity of phosphorus released from sediments under light irradiation and aerobic conditions was much higher than that in an anoxic environment. In the anoxic condition, the main released fraction of phosphorus in the sediment was Fe-P, and the concentration of Ca-P increased only a little. However, under aerobic conditions, the concentration of Fe-P had no obvious changes, and Ca-P declined slightly in the light. No obvious changes were found for the concentration of total phosphorus, organic or residual phosphorus.