铁对高原喀斯特人工湖中产毒微囊藻生长与光合作用、产毒及种群优势的影响规律研究

Cyanobacteria bloom has become a major environmental problem. The relationship between nitrogen and phosphorus content in the lakes and cyanobacteria bloom has been focused for a long time. The concentration of available iron affected the growth and photosynthesis, community structure and synthesis of microcystins of the algae. Trace metal clean technologies will be used in this research, and Lake Hongfeng as a Karst plateau artificial lake in Guiyang will be researched. First, the seasonal variations in different iron species concentrations, microcystin-producing Microcystis abundances as well as intracellular and extracellular microcystins production in Lake Hongfeng will be surveyed. Then field enclosure experiments followed by laboratory culture experiments will be carried out in order to compare different responses among growth and photosynthesis, abundances of microcystin-producing Microcystis as well intracellular and extracellular microcystins production under different concentrations of available iron. Finally, we will explore the possible role of intracellular and extracellular microcystins in adaptating to iron limitation and maintaining the population advantage for microcystin-producing Microcystis under iron stress, through competition culture experiments. This study not only help us to clarify the effects of iron in maintaining the population advantage for microcystin-producing Microcystis and toxin production, but also help us to provide a new idea to control cyanobacteria blooms by controlling the available iron concentration in the lake.

蓝藻水华已成为重大的环境问题，湖泊中氮磷含量与蓝藻水华的关系是人们长期关注的焦点。可利用铁浓度影响了藻类的生长和光合作用、群落结构及微囊藻藻毒素的合成。本项目采用痕量金属洁净技术，以贵阳高原喀斯特人工湖红枫湖为研究水体。首先调查分析贵阳红枫湖中各种形态铁含量与产毒微囊藻丰度、胞内外藻毒素含量的季节变化规律。再以现场围隔实验和室内培养实验，比较产毒微囊藻与其它藻株的生长和光合作用、种群丰度以及胞内外藻毒素含量对铁限制的响应差异。最后通过比较铁限制对产毒微囊藻和其它藻类的竞争实验，探讨胞内外微囊藻毒素在产毒微囊藻适应低铁限制并维持种群优势中的可能作用。该研究不仅有助于阐明铁对产毒微囊藻种群优势和产毒的影响规律，更有助于为蓝藻水华的治理提供新的思路，通过控制湖泊中可利用铁浓度来防控水华蓝藻。

湖泊中铁含量与蓝藻水华的关系缺乏关注。本研究调查了贵州高原喀斯特人工湖红枫湖不同形态铁及氮磷含量、水质参数、主要光合色素含量、代表性浮游植物以及产毒与非产毒微囊藻种群丰度、主要微囊藻毒素含量等的时空变化；分析了培养瓶内氮磷铁等营养盐及铁螯合剂室外添加实验水样的pH值和溶解氧等水质参数、主要光合色素含量、叶绿素荧光、代表性藻类种群丰度及微囊藻毒素含量的变化；比较了铁限制对代表性蓝藻和绿藻生长与光合作用的影响差异；揭示了铁限制对产毒微囊藻与假鱼腥藻以及斜生栅藻竞争的影响规律。结果表明，红枫湖优势种主要为微囊藻、假鱼腥藻等蓝藻，较高的温度光照以及氮磷铁等营养盐含量导致夏秋季节红枫湖水体中产毒微囊藻种群丰度较大且微囊藻毒素含量较高；铁螯合剂8-羟基喹啉添加抑制了假鱼腥藻以及产毒、非产毒微囊藻等蓝藻的生长与光合作用，单独的磷添加较大的促进了藻类的生长、光合作用以及产毒，氮磷铁同时添加对产毒微囊藻等藻类的生长与光合作用促进作用最大；产毒微囊藻、假鱼腥藻、四尾栅藻三个藻株的生长与光合作用受铁限制的影响较大；铁限制条件下，产毒微囊藻促进了假鱼腥藻和斜生栅藻的生长。但在铁充足条件下假鱼腥藻的生长受到抑制而斜生栅藻的生长无显著影响，且假鱼腥藻和斜生栅藻促进了产毒微囊藻胞内外毒素含量的升高。因此，应加强夏秋季节红枫湖微囊藻水华的动态监测和预警，红枫湖蓝藻水华的防控与治理以控制磷含量为主并同时控制铁含量，红枫湖水体中可利用铁浓度将会影响到产毒微囊藻生长、光合作用、种群优势以及毒素的合成与释放。