• 关键词：颗粒态有机碳  来源  碳稳定同位素  蓝藻  碳氮比

• 基金项目：国家自然科学基金（No.41201076，91547119）

• 叶琳琳
• 南通大学地理科学学院, 南通 226000

• 吴晓东
• 中国科学院西北生态环境资源研究院, 冰冻圈科学国家重点实验室, 青藏高原冰冻圈观测研究站, 兰州 730000

• 闫德智
• 南通大学地理科学学院, 南通 226000

• 刘波
• 南通大学地理科学学院, 南通 226000

• 摘要：以太湖重度蓝藻水华发生的西北湖区为研究对象，从河口到湖心区设置5个采样点，于2012年9月—2013年8月逐月采集表层水体样品，测定了水温、蓝藻生物量和总细菌丰度，并分析了颗粒态有机碳（POC）、溶解性有机碳（DOC）含量及颗粒态有机物（POM）的碳稳定同位素特征值（δ¹³C_POM）和碳氮比（C/N）.结果表明，与DOC相比，太湖西北湖区表层水体POC含量变化范围较大，为（0.49±0.03）~（30.86±2.00）mg·L^-1，冬季POC含量较低，春季和夏季POC含量达到最大值.降雨冲刷作用产生的悬浮物随着地表径流进入水体可能是引起汛期POC/DOC升高的重要原因.鉴于太湖水体风场影响下表层湖流作用会引起蓝藻在西北湖区堆积，5个采样点的蓝藻生物量没有显著差异.POC含量的差异仅存在于靠近陈东港的河口区S5与湖心S4之间（p<0.05，n=10）.蓝藻生物量与POC含量（r=0.634，n=48，p<0.01）、δ¹³C_POM（r=0.500，n=48，p<0.01）均显著正相关，表明蓝藻是太湖西北湖区表层水体POC的来源之一.西北湖区秋、冬季δ¹³C_POM显著低于春、夏季（p<0.001，n=57），均值（-25.9‰±6.37‰）介于太湖δ¹³C_微囊藻（-20.9‰）和外源来源端元的碳稳定同位素特征值（-27‰）之间，表明内源和外源来源都是太湖西北湖区表层水体POC的来源，夏季表层水体POC的主要来源是内源，冬季河口区S5的主要来源是外源.POM碳氮比有显著季节变化规律，秋、冬季较春、夏季高（p<0.001，n=55），平均值（9.36±2.80）较低，可能是内源来源POC及外源POC被细菌生物降解的结果.

• Abstract：During September 2012 to August 2013, the surface water samples were collected in the northwest of Lake Taihu, which experienced severe cyanobacterial blooms, at five sites from the estuary to the lake center. Water temperature, cyanobacterial biomass, and total bacterial abundance were analyzed, as well as the concentrations of particulate (POC) and dissolved organic carbon (DOC), stable carbon isotope values (δ¹³C_POM) and carbon to nitrogen ratio (C/N) of particulate organic matter (POM). The results showed that POC, ranging from (0.49±0.03) to (30.86±2.00) mg·L^-1, was more variable than DOC. POC concentration was relatively low in winter, and the maximum values were observed in spring and summer. The POC/DOC ratios were higher than 1, which could be attributed to the rainfall-induced suspended matter. Since wind-driven lake currents caused the accumulation of cyanobacteria in the northwest of Lake Taihu, no significant difference in cyanobacterial biomass was observed among the five sampling sites. A significant difference in POC concentration was observed between the site (S5) near to the estuary (Chendonggang River) and the site (S4) located at the lake center (p<0.05,n=10).Cyanobacterial biomass was positively correlated with both POC (r=0.634,n=48,p<0.01) and δ¹³C_POM (r=0.500,n=48,p<0.01), suggesting that cyanobacterial bloom was probably a source of POC in the surface water in the northwest of Lake Taihu. The δ¹³C_POM during autumn-winter were significantly lower than those during spring-summer (p<0.001,n=57). The averaged δ¹³C_POM (-25.9‰±6.37‰) fell in between the stable carbon isotope value of Microcysits(-20.9‰) and that of allochthonous origin(-27‰), indicating that both autochthonous and allochthonous contributed to the POC. Autochthonous source dominated in summer and allochthonous source dominated in S5 in winter. The carbon to nitrogen ratios of POM showed a seasonal variation and were low during autumn-winter in comparison with those during spring-summer (p<0.001,n=55). The relatively low carbon to nitrogen ratios of POM(9.36±2.80)on average could be explained by the biodecomposition of both autochthonous POC and allochthonous POC.

• Key words：particulate organic carbon  source  stable carbon isotope  cyanobacteria  carbon to nitrogen ratio

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