Strategies of amino acid supply in mesozooplankton during cyanobacteria blooms: a stable nitrogen isotope approach
Strategies of amino acid supply in mesozooplankton during cyanobacteria blooms: a stable nitrogen isotope approach
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DOI：
10.1002/ecs2.2135
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发表时间：
2018-03-01
期刊：
影响因子：
2.7
通讯作者：
Loick-Wilde, Natalie
中科院分区：
文献类型：
--
作者：
Eglite, Elvita;Wodarg, Dirk;Loick-Wilde, Natalie
浮游动物如何利用蓝藻来维持其氮（N）的必需化合物，如氨基酸（AAs）的需求的知识是预测未来增强水柱分层的生产和食物网结构方面的高营养级的响应的关键。我们探讨了天然丰度的散装N和AA-特定的氮同位素（N-15）颗粒有机物和中型浮游动物的尺寸分数样品从三个垂直分离的水体在波罗的海中部在两个夏季蓝藻水华。浮游生物群落和同位素数据与环境变量相结合，有助于确定固氮AA供应（N-2固定过程中合成）的中型浮游动物的机制，这在很大程度上取决于海面温度，调节获得固氮N-为基础的食物网在地表水（SW）。我们发现，在温暖的夏天，嗜热枝角类（例如，Bosmina spp.）在西南部（19.8摄氏度），从固氮型AAs中受益最多，而只有在较冷的夏季，温带桡足类（例如，Temora longicornis）上升到西南（16.2摄氏度）从subjacent冬季水，并纳入重氮营养AA。营养位置估计的基础上的苯丙氨酸和谷氨酸N-15签名显示，重氮营养AA供应到中型浮游动物主要是间接通过喂养的混合和异养饮食。显着丰富的N-15签名苯丙氨酸在深层浮游动物（主要桡足类的伪和拟哲水蚤属）。从底层水（BW），这是一个地区的亚氧区点依赖于当地的食物网。中浮游动物在BW的饮食的异养起源和可能受益于异养再合成的AAs来源于下沉的有机物，以及从头合成的AAs，最有可能起源于化能自养细菌或古菌群落的亚氧区的间接掺入。研究结果表明，在未来的强化分层水生系统中，对固氮生物和化能自养生物的间接摄食将是浮游动物氨基酸供给的主要途径。只有一个相对较小的温度上升可能会限制温带关键物种的固氮氮基食物网中的混合层。
Knowledge of how zooplankton can utilize cyanobacteria to sustain their nitrogen (N) demand for essential compounds like amino acids (AAs) is a key to predicting responses of higher trophic levels in terms of production and food web structure to future enhanced water column stratification. We explored the natural abundances of bulk N and AA-specific nitrogen isotopes (N-15) in particulate organic matter and mesozooplankton size-fraction samples from three vertically separated water bodies in the central Baltic Sea during two summertime cyanobacteria blooms. The combination of plankton community and isotope data together with environmental variables helped to identify a mechanism of diazotrophic AA supply (synthesized during N-2 fixation) for mesozooplankton, that largely depended on the sea surface temperature which regulated the access to the diazotrophic N-based food web in the surface water (SW). We found that in the warmer summer, thermophilic cladocerans (e.g., Bosmina spp.) benefited most from diazotrophic AAs in the SW (19.8 degrees C), while only in the colder summer, temperate copepods (e.g., Temora longicornis) ascended from the subjacent winter water into the SW (16.2 degrees C) and incorporated diazotrophic AAs. Trophic position estimates based on the phenylalanine and glutamic acid N-15 signatures revealed that the diazotrophic AA supply into mesozooplankton was mainly indirect via feeding on mixo- and heterotrophic diets. Significantly enriched N-15 signatures in phenylalanine in the deep mesozooplankton (mainly copepods of Pseudo- and Paracalanus spp.) from the bottom water (BW) that was a region of the suboxic zone point to a reliance on a local food web. Mesozooplankton in the BW was feeding on diets of heterotrophic origin and probably profited from the heterotrophic re-synthesis of AAs originating from sinking organic matter, as well as from the indirect incorporation of de novo synthesized AAs that most likely originated from chemoautotrophic bacteria or archaea communities in the suboxic zone. Our findings suggest that indirect feeding on diazotrophs and chemoautotrophs will be principal ways of amino acid supply for zooplankton in future enhanced stratified aquatic systems. Only a relatively small increase in temperature may restrict temperate key species from diazotrophic N-based food webs in the mixed layer.