Phytoplankton community characteristics and the underlying drivers under organic and conventional agricultural management

Abstract

为了解不同农业施肥管理方式对水体浮游植物群落的影响，本研究以江苏句容戴庄有机示范村和常规农业管理区池塘浮游植物为对象，分析冬夏两季浮游植物群落特征及相关水环境因子.结果表明：冬季有机和常规农业区域的浮游植物分别检到7门95种和7门111种，夏季分别检到7门102种和6门112种，有机农业区浮游植物由冬季的隐藻-绿藻型向夏季的蓝藻-绿藻型变化，常规农业区从隐藻-绿藻型向蓝藻-硅藻型变化，蓝藻逐渐取代隐藻的优势地位.夏季各池塘浮游植物alpha多样性没有显著的区域差异，但冬季常规农业区浮游植物物种丰富度、蓝藻和裸藻的Shannon-Wiener多样性指数显著较高.指示物种分析显示，谷皮菱形藻（Nitzschia palea）和梅尼小环藻（Cyclotella meneghiniana）为有机农业区指示物种，而梭形裸藻（Euglena acus）、针形纤维藻（Ankistrodesmus acicularis）、肘状针杆藻（Synedra ulna）和狭形纤维藻（Ankistrodesmus angustus）为常规农业区指示物种，此6种藻为中、富营养化藻类，说明水体氮磷营养盐浓度较高，这与周围农田氮磷流失密切相关.Pearson相关性分析表明，有机农业区浮游植物alpha多样性与氮磷浓度的相关性不显著，但常规农业区浮游植物物种丰富度和Pielou均匀度与磷酸盐、总氮、氨氮和pH值显著相关.Mantel检验表明，有机农业区群落相异性仅在冬季受到总氮和氨氮的显著影响；而常规农业区在冬夏季受到氮磷两类营养盐的交替影响.本研究结果初步揭示了有机和常规农业区水体浮游植物群落结构特征及其影响因素，为区域水生生物多样性保护与稻田施肥管理的优化提供科学基础.;In order to explore the effects of different agricultural fertilization management on the phytoplankton community, the phytoplankton community characteristic and water environmental factors were investigated in winter and summer in Daizhuang organic village and conventional farming area of Jurong, Jiangsu Province. Our results showed that the phytoplankton communities were composed of 95 and 111 species of 7 phyla in organic (OFR) and conventional farming regions (CFR) in winter, 102 species of 7 phyla and 112 species of 6 phyla in summer, respectively. The phytoplankton varied from Cryptophyta-Chlorophyta type in winter to Cyanophyta-Chlorophyta type in summer in OFR, and from Cryptophyta-Chlorophyta type to Cyanophyta-Bacillariophyta type in CFR, indicating that Cyanophyta gradually replaced the dominant position of Cryptophyta. There was no significant difference in phytoplankton alpha diversity between organic and conventional farming ponds in summer, but the phytoplankton species richness and Shannon-Wiener diversity of Cyanophyta and Euglenophyta in CFR was significantly higher than that in OFR in winter. The IndVal analysis further revealed that Nitzschia palea and Cyclotella meneghiniana were the indicative species in OFR, while Euglena acus, Ankistrodesmus acicularis, Synedra ulna and Ankistrodesmus angustus were the indicative species in CFR. These algae often occurred in meso-eutrophic waters, indicating that the concentration of nitrogen and phosphorus in water was higher. This may be closely related to the nitrogen and phosphorus runoff. Pearson correlation analysis showed that there was no significant relationship between phytoplankton alpha diversity and environmental factors in two regions, but species richness and Pielou's evenness in CFR were significantly correlated with phosphate, total nitrogen, ammonia nitrogen and pH. Mantel test showed that the community dissimilarity in OFR was only significantly affected by total nitrogen and ammonia nitrogen in winter. While in CFR, community dissimilarity was affected by the alternation of nitrogen and phosphorus nutrients in winter and summer. These findings should be useful for future efforts to recover biodiversity and optimize fertilization management.