Biomarker and carbon isotopic constraints on bacterial and algal community structure and functioning in a turbid, tidal estuary
Biomarker and carbon isotopic constraints on bacterial and algal community structure and functioning in a turbid, tidal estuary
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DOI：
10.4319/lo.2005.50.1.0070
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发表时间：
2005-01-01
影响因子：
4.5
通讯作者：
Middelburg, JJ
中科院分区：
文献类型：
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作者：
Boschker, HTS;Kromkamp, JC;Middelburg, JJ
利用化合物特异性C-13分析方法研究了Scheldt河口沿岸春季水华期间磷脂衍生脂肪酸（PLFA）的浮游生物群落结构和同位素组成。还确定了一套全面的其他碳循环参数。根据溶解的二氧化碳和氧气浓度以及原生和次生细菌产量，河口的营养状态由上游的强烈净异养向下游的净自养转变。藻类PLFA和色素浓度以及优势浮游植物的显微鉴定也显示出相同的趋势：淡水浮游植物以绿藻和硅藻混合群落为主，中盐度以硅藻华为主。河口下游硅藻华的细菌生物量（同样基于PLFA）远低于净异养河口上游。硅藻主要标志物PLFA （20:5 omega3）的碳同位素比值主要与溶解无机碳δ (13)C值的变化有关，剩余变化幅度接近5%，可能与河口沿岸生长条件的变化有关。绿藻标记物18:3omega3在碳-13中的耗竭程度远高于硅藻标记物，这表明这两种主要浮游植物群使用不同的无机碳源或二氧化碳固定机制。检测到的不同细菌PLFA的同位素比率非常相似，范围在-30%到-21%之间。他们密切跟踪了颗粒有机碳（POC）中的δ (13)C值，表明POC或具有相同C-13特征的物质是主要的细菌碳基质。在河口较低的海洋一侧，细菌和藻类PLFA的同位素比率相似，表明有机物的初级生产和细菌消耗之间存在耦合。然而，与藻类PLFA相比，河口上游细菌PLFA的δ (13)C值更丰富（在6 - 15‰之间），表明这是一个不耦合的藻-细菌系统，有外来补贴，如陆地C3有机质或污水支持细菌生长。
We studied planktonic community structure and isotopic composition using compound-specific C-13 analysis of phospholipid-derived fatty acids (PLFA) along the Scheldt estuary during a spring bloom. A comprehensive set of other carbon cycle parameters was also determined. Based on dissolved carbon dioxide and oxygen concentrations and primary and bacterial secondary production, the trophic status of the estuary changed from strongly net heterotrophic in the upper to net autotrophic in the lower estuary. Concentrations of algal PLFA and pigments and microscopic identifications of dominant phytoplankton revealed the same trend: a mixed community of green algae and diatoms dominated the freshwater phytoplankton and there was a major diatom bloom at intermediate salinities. Bacterial biomass (also based on PLFA) was much lower for the diatom bloom in the lower estuary than in the net heterotrophic upper estuary. Carbon isotopic ratios of the main diatom marker PLFA, 20: 5omega3, were mainly related to changes in delta(13)C values of dissolved inorganic carbon and showed a residual variation of similar to5% which is probably related to changes in growth conditions along the estuary. The green algal marker 18:3omega3 was much more depleted in C-13 than the diatom markers, suggesting that these two main phytoplankton groups use a different inorganic carbon source or carbon dioxide fixation mechanism. Isotopic ratios of the different bacterial PLFA detected were very similar and ranged between -30% and -21%o. They closely tracked delta(13)C values in particulate organic carbon (POC), indicating that POC or material with the same C-13 signature was the main bacterial carbon substrate. In the lower, marine side of the estuary, isotope ratios of bacterial and algal PLFA were similar, suggesting a coupling between primary production and bacterial consumption of organic matter. However, delta(13)C values of bacterial PLFA in the upper estuary were enriched compared with algal PLFA (between 6parts per thousand and 15parts per thousand), indicating an uncoupled algal-bacterial system with allochthonous subsidies, such as terrestrial C3 organic matter or sewage supporting bacterial growth.