典型湖泊有机聚集体时空特征及驱动因子

Spatio-temporal Characteristics of Organic Aggregates and the Driving Factors in Typical Lakes

有机聚集体(OA)是水体中物质循环和能量流通的重要枢纽,但在不同营养水平湖泊中的比较研究仍相当匮乏.于2019~2021年间,采集了不同季节贫营养抚仙湖、中营养天目湖、中度富营养太湖和重度富营养星云湖表层水样,利用扫描电镜、表面荧光显微镜和流式细胞仪等研究了4个典型湖泊中OA及其附着细菌的时空变化特征.结果表明:(1)抚仙湖、天目湖、太湖和星云湖中,OA丰度的年均值分别为1.4×10^(4)、 7.0×10^(4)、 27.7×10^(4)和16.0×10^(4)ind·mL^(-1);OA附着细菌丰度的年均值分别为0.3×10^(6)、 1.9×10^(6)、 4.9×10^(6)和6.2×10^(6)cells·mL^(-1);附着细菌占总细菌的比值分别为30%、 31%、 50%和38%.(2)夏季OA丰度显著高于秋冬季;但夏季附着细菌占总细菌的比值为26%,显著低于其它3个季节.(3)湖泊营养状态是影响OA及其附着细菌丰度的最重要环境因子,可单独解释OA及其附着细菌丰度时空变化的50%和68%.(4)OA上富含营养盐和有机质,尤其是星云湖,其OA中颗粒态磷和氮占比高达69%和59%,有机质占比达79%.未来气候变化和湖泊藻类水华扩张背景下,藻源性OA在有机质矿化降解及营养盐循环中的作用可能会进一步加大.

Organic aggregates(OA)are the important circulation hub of matter and energy in aquatic ecosystems.However,the comparison studies on OA in lakes with different nutrient levels are limited.In this study,spatio-temporal abundances of OA and OA-attached bacteria(OAB)in oligotrophic Lake Fuxian,mesotrophic Lake Tianmu,middle-eutrophic Lake Taihu,and hyper-eutrophic Lake Xingyun were investigated in different seasons during 2019-2021 using a scanning electron microscope,epi-fluorescence microscope,and flow cytometry.The results showed that:①the annual average abundances of OA in Lake Fuxian,Lake Tianmu,Lake Taihu,and Lake Xingyun were 1.4×10^(4),7.0×10^(4),27.7×10^(4),and 16.0×10^(4) ind·mL^(-1),whereas the annual average abundances of OAB in the four lakes were 0.3×10^(6),1.9×10^(6),4.9×10^(6),and 6.2×10^(6) cells·mL^(-1).The ratios of OAB:total bacteria(TB)in the four lakes were 30%,31%,50%,and 38%,respectively.②OA abundance in summer was significantly higher than that in autumn and winter;however,the ratio of OAB:TB in summer was approximately 26%,which was significantly lower than that in the other three seasons.③Lake nutrient status was the most important environmental factor that affected the abundance variations of OA and OAB,accounting for 50%and 68%of the spatio-temporal variations in OA and OAB abundances.④Nutrient and organic matters were enriched in OA,especially in Lake Xingyun;the proportions of particle phosphorous,particle nitrogen,and organic matters in this lake were as high as 69%,59%,and 79%,respectively.Under the circumstance of future climate change and the expansion of lake algal blooms,the effects of algal-originated OA in the degradation of organic matters and nutrient recycling would be increased.