不同类型化感物质抑制蓝藻效益比较及联合抑藻效应评述

A REVIEW ON ANTIALGAL EFFECTIVENESS AMONG DISTINCT ALLELOCHEMICALS AND JOINT INHIBITORY EFFECTS ON CYANOBACTERIAL GROWTH

世界范围内的蓝藻水华持续威胁着水生生态系统功能和人类健康,化感物质凭借其环境安全和对微藻有特异毒性等特征可以短期抑制蓝藻水华的暴发和生长。文章分别概括了酚类化合物、含氮化合物、脂肪酸/酯类、萜类化合物四类化感物质及其衍生物对蓝藻的杀藻效果、潜在机制及特异作用靶点,并依据高效抑藻化感物质(EC_(50)<10 mg/L)的经济成本进一步预估其实际应用潜能。结果表明,单独胁迫下的各类化感物质具不同抑藻特性:脂肪酸/酯类的性价比最优,能以较少剂量对蓝藻产生极强毒性,对蓝藻多样的作用靶点是其具有极强抑制效果的关键,可在0.015-52.95 mg/L浓度范围内将目标蓝藻抑制50%;酚类化合物总数最多、活性普遍较高,半数效应浓度(EC50)为0.05-162.53 mg/L,可通过抑制光合作用、破坏细胞氧化应激平衡和损害细胞壁/膜结构等多种机制抑制蓝藻生长,但高效杀藻酚类化合物的理论成本差异较大,性价比次于脂肪酸位于第二位;含氮化合物对蓝藻生长存在特异性和均匀高效的杀藻作用, EC50集中于0.3-8.14 mg/L,主要通过破坏蓝藻的光合作用、阻断电子传递和破坏细胞结构(包括超微结构)而对蓝藻造成不可逆转的严重损伤,但成本较高、性价比最低而难以广泛实际应用;萜类化合物杀藻作用弱于其他三个类别的化感物质,主要集中于多途径破坏蓝藻细胞的光合功能,但EC50高达25.3-228 mg/L,实际应用也受限。为减少各种化感物质用量、降低经济成本并实现更高效的杀藻效果,文章总结归纳相同和不同类型化感物质联合作用方式和特点,指出化感物质所产生的联合作用效果取决于混合化感物质的数量、作用靶点、混合比例和混合物含量四个因素。综述还提出抑藻靶点多样且互补的化感物质混合(“多靶点组合”)可产生协同杀藻作用,且在混合物中应增加具有高杀藻活性化感物质的比例(“新木桶效应”协同效应)。同时指出依据植物实际分泌物的种类、含量及比例进行多元混合抑藻更易出现协同杀藻作用,为科学、综合、合理地选择和应用化感物质并优化其配比以控制蓝藻水华提供新见解。

Cyanobacterial blooms worldwide pose severe threat to aquatic ecosystem functions and even human health.Due to environmental-friendliness and high selectivity, allelochemicals have put forward a promising option for inhibiting cyanobacterial overgrowth and therefore mitigating blooms in a short term. This study overviewed the algicidal effects of four types of allelochemicals, i.e., polyphenolics, nitrogen-containing compounds, fatty acids/esters and terpenoids, as well as underlying mechanisms and specific target sites against cyanobacteria, and further evaluated the application potential based on economic costs of highly effective cyanobacterium-inhibiting allelochemicals. The results demonstrated distinctive algicidal characteristics among each type of allelochemicals: Fatty acids/esters were the most cost-effective in algicidal activity, which induced extremely strong toxicity to cyanobacteria at low doses due to various action targets and suppressed target cyanobacterial growth by 50% in concentration range of 0.015-52.95 mg/L;Polyphenolics as the most abundant allelochemicals generally exhibited high algicidal activity with median effect concentration(EC50) ranging from 0.05 to 162.53 mg/L, and could restrain cyanobacterial growth by multiple mechanisms such as inhibiting photosynthesis, disrupting cellular oxidative stress balance and damaging cell wall/membrane structure. However, the theoretical costs vastly differed among highly effective algicidal polyphenolics, whose cost-efficiencies were inferior to fatty acids and thus ranked as 2nd place following fatty acids;N-containing compounds generally exhibited specific and evenly effective algicidal effect against cyanobacterial growth, with EC50varying from 0.3 to8.14 mg/L, and induced irreversible cell damage by mainly disrupting cyanobacterial photosynthesis, blocking electron transfer, and destroying cellular structures(including ultrastructure). However, N-containing compounds involved high costs and lowest effectiveness that hindered their wide application. Terpenoids exhibited relatively weak algicidal effect as compared to other three types of allelochemicals, which exerted algicidal effect through multi-routes to mainly disrupt photosynthetic function of cyanobacterial cells, with higher EC50reaching up to 25.3-228 mg/L that limited their actual application. Consequently, this review summarized joint action effect modes and characteristics of same type and different types of allelochemicals on cyanobacterial(mainly Microcystis aeruginosa) growth to decrease applying dosages of allelochemicals, diminish economic costs and achieve more efficient algicidal effects, and pointed out that allelochemicals number in mixture, action target sites, each allelochemical proportion in mixture and mixture dosage were key factors to determine joint action effect of mixed allelochemicals. This review also proposed that different allelochemicals with diverse and complementary action target sites(referred as ‘multi-target mixture’) could exert synergistic effects, and that proportions of allelochemicals with high algicidal activity should be increased in mixture(referred as ‘new-barrel effect’ synergistic effect). Moreover, this review also proposed that multiple allelochemicals were more likely to arouse synergistic algicidal effects when they were mixed based on their inherent types, contents and proportions actually excreted by plants, which provided novel insights for scientific, comprehensive and reasonable choice, application and optimally mixing of allelochemicals, in controlling cyanobacterial blooms.