Factors controlling seasonal variations in stable isotope composition of particulate organic matter in a soft water eutrophic lake
Factors controlling seasonal variations in stable isotope composition of particulate organic matter in a soft water eutrophic lake
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DOI：
10.4319/lo.2006.51.6.2837
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发表时间：
2006-11-01
影响因子：
4.5
通讯作者：
Schelske, Claire L.
中科院分区：
文献类型：
--
作者：
Gu, Binhe;Chapman, Andrew D.;Schelske, Claire L.
从1994年6月至1995年5月，在佛罗里达的沃伯格湖，每周取水样测量颗粒有机物（POM）的稳定同位素组成（δ C-13和δ N-15）。POM的平均δ C-13为千分之-19.3，与浮游植物生产的本地起源一致，并表现出与水温，pH值，CO2浓度和地表水浮游植物生物量的变化相吻合的季节性模式。POM中的C-13富集归因于碳（C）限制导致的同位素分馏减少以及主要由大气入侵和无氧呼吸支持的同位素重溶解无机碳库的使用。POM的三角洲C-13的间歇性下降与浮游植物水华的频繁崩溃和CO2浓度的增加导致的社区呼吸和陆地负荷的增加有关。POM的平均Δ N-15为1.3份/千份，并且在很窄的范围内变化（-0.1份/千份至2.5份/千份）。POM的N-15值与浮游植物生物量之间没有显著的相关性，N-15值较低表明水体具有较强的N-2固定能力，这与水体中溶解性无机氮浓度较低以及固氮蓝藻生物量较高相一致。本研究表明，稳定的碳同位素是很好的代理地表水CO2浓度和初级生产力，而稳定的N同位素可以用来指示N-2固定。
Weekly water samples were taken to measure stable isotope composition (delta C-13 and delta N-15) of particulate organic matter (POM) in Lake Wauberg, Florida, from June 1994 to May 1995. The average delta C-13 of POM was -19.3 parts per thousand, consistent with an autochthonous origin from phytoplankton production, and exhibited a seasonal pattern that coincided with changes in water temperature, pH, CO2 concentration, and phytoplankton biomass in the surface water. The C-13 enrichment in POM was attributed to reduced isotope fractionation due to carbon (C) limitation and the use of an isotopically heavy dissolved inorganic carbon pool supported mainly by atmospheric invasion and anaerobic respiration. Intermittent declines in delta C-13 of POM were related to the frequent collapses of phytoplankton blooms and increases in CO2 concentration resulting from both increased community respiration and terrestrial loading. Average delta N-15 of POM was 1.3 parts per thousand and varied within a narrow range (-0.1 parts per thousand to 2.5 parts per thousand). No significant correlation between phytoplankton biovolume and the delta N-15 of POM was found. The low delta N-15 is indicative of strong N-2 fixation, which is in line with the low concentration of dissolved inorganic nitrogen and the presence of high biovolume of N-2-fixing cyanobacteria in the surface water. This study suggests that stable C isotopes are good proxies for surface water CO2 concentration and primary production, while stable N isotopes can be used to indicate N-2 fixation.