铜绿微囊藻(Microcystis aeruginosa)次生代谢物对普通小球藻(Chlorella vulgaris)生长及有效量子产率的影响

Effects of Microcystis aeruginosa' secondary metabolites on growth and effective quantum yield of Chlorella vulgaris

浮游植物间的交互化感作用被认为是自然水体中浮游生物群落演替及优势种转换的主要因素之一.铜绿微囊藻(Microcystis aeruginosa)是富营养化湖泊中的常见蓝藻,其产毒品系相较非产毒品系具有较高的竞争优势,其产生的主要次生代谢产物微囊藻毒素-LR(MC-LR)通常被认为是重要的化感物质.但是到目前为止其在水生生态系中的生物学功能尚不明确.为探究并区分MC-LR及其他次生代谢产物对浮游植物的化感效应,本文研究了MC-LR与高浓度普通小球藻(Chlorella vulgaris)生长及有效量子产率的剂量—效应关系;比较了能够产生显著抑制效应的MC-LR、能够产生同等浓度MC-LR的产毒品系铜绿微囊藻滤液以及细胞粗提液对小球藻生长及有效量子产率的抑制效应.结果显示,MC-LR能够对小球藻生长及有效量子产率产生抑制作用,并且抑制率随着MC-LR浓度的增加而增大.在用200μg/L及以上浓度的MC-LR感染24 h后,叶绿素a浓度为1500μg/L的小球藻的生长与有效量子产率均比对照组显著降低.能够产生相同浓度MC-LR的产毒品系铜绿微囊藻细胞滤液对其没有产生显著影响,而其细胞粗提液却能够产生更强的抑制效应.与MCLR处理组相比,粗提液处理组小球藻的生长及有效量子产率分别降低了14%和3%.以上结果表明,MC-LR对普通小球藻的化感作用具有剂量依赖性;MC-LR之外的其他次生代谢物也能够产生抑制效应.

Allelopathic interactions among phytoplankton species are regarded as one of the important factors contributing to their dominance and succession in natural waters.Microcystis aeruginosa is a cyanobacterial species commonly found in eutrophic lakes,and microcystin-LR(MC-LR),the mainly secondary metabolite in its cells is usually regarded as allelochemical.However,the biological role of this molecule in the aquatic ecosystem is still under discussion.To explore and distinguish the allelopathic effects of MC-LR and other secondary metabolites on phytoplankton,the dose-effects relationships between MC-LR and growth as well as effective quantum yield of Chlorella vulgaris were investigated.In addition,the different responses of C.vulgaris exposed to pure MC-LR(200μg/L)that has been proved to induce negative effects,the cell-free filtrates and crude extracts of toxic M.aeruginosa FACHB-905 in cell concentration containing the same content of MC-LR were compared.The results showed that MC-LR decreased the growth and effective quantum yield of C.vulgaris,and the inhibition efficiency increased with enhanced MC-LR concentration.Contamination with MC-LR≥200μg/L significantly inhibited the growth and effective quantum yield of C.vulgaris in concentration of 1500μg/L chlorophyll-a within 24 h.The cell-free filtrates of toxic M.aeruginosa FACHB-905 had no significant negative effects on C.vulgaris.However,compared with the pure MC-LR,the crude extracts of toxic M.aeruginosa FACHB-905 containing the same amount of MC-LR led to further inhibition.Compared with the MC-LR treated one,the growth and effective quantum yield of C.vulgaris treated with the crude extracts was further decreased by 14%and 3%,respectively.The results indicated that the allelopathic effects of MC-LR on its co-existing phytoplankton species were dose-dependent,and the secondary metabolites other than MC-LR also had negative effects.