Saharan Dust Deposition Effects on the Microbial Food Web in the Eastern Mediterranean: A Study Based on a Mesocosm Experiment
Saharan Dust Deposition Effects on the Microbial Food Web in the Eastern Mediterranean: A Study Based on a Mesocosm Experiment
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DOI：
10.3389/fmars.2017.00117
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发表时间：
2017-05
影响因子：
3.7
通讯作者：
P. Pitta;M. Kanakidou;N. Mihalopoulos;S. Christodoulaki;Panagiotis D. Dimitriou;C. Frangoulis;A. Giannakourou;Margarita Kagiorgi;A. Lagaria;P. Nikolaou;N. Papageorgiou;S. Psarra;Ioulia Santi;M. Tsapakis;A. Tsiola;K. Violaki;G. Petihakis
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作者：
P. Pitta;M. Kanakidou;N. Mihalopoulos;S. Christodoulaki;Panagiotis D. Dimitriou;C. Frangoulis;A. Giannakourou;Margarita Kagiorgi;A. Lagaria;P. Nikolaou;N. Papageorgiou;S. Psarra;Ioulia Santi;M. Tsapakis;A. Tsiola;K. Violaki;G. Petihakis
2014年5月，在营养贫乏的地中海东部，通过中层实验研究了撒哈拉沙尘沉积事件对中上层微生物食物网的影响。采用两种不同的处理方法(一次强脉冲或连续三次加入相同总量的较小剂量的撒哈拉沙漠天然粉尘)，以及三个未经修正的对照；在为期10天的实验中测量了化学和生物参数。研究了初级(PP)和细菌(BP)产量、叶绿素a(Chla)浓度以及异养细菌、聚球藻和中游动物丰度的时间变化。结果表明，粉尘(以及通过粉尘添加的氮和磷)增强了食物网(至少是原核生物)的自养和异养成分。此外，每天加入三种剂量的粉尘，PP、BP和Chla的增加都有1d的延迟，但两种处理达到的最大值相似。虽然这种影响在第一渗透营养级(浮游植物和细菌)很明显，但在异养鞭毛虫、纤毛虫和甲藻等捕食者施加的放牧影响下，它在食物网上消失得更远。两次稀释实验部分证明了这一点。这项研究表明，在评估大气沉积和原生生物放牧对以营养水平增加为特征的寡营养系统的影响时，大气沉积和原生生物放牧的重要作用。
The effect of episodicity of Saharan dust deposition on the pelagic microbial food web was studied in the oligotrophic Eastern Mediterranean by means of a mesocosm experiment in May 2014. Two different treatments in triplicates (addition of natural Saharan dust in a single-strong pulse or in three smaller consecutive doses of the same total quantity), and three unamended controls were employed; chemical and biological parameters were measured during a 10-day experiment. Temporal changes in primary (PP) and bacterial (BP) production, chlorophyll a (Chla) concentration and heterotrophic bacteria, Synechococcus and mesozooplankton abundance were studied. The results suggested that the auto- and hetero-trophic components of the food web (at least the prokaryotes) were enhanced by the dust addition (and by the nitrogen and phosphorus added through dust). Furthermore, a 1-day delay was observed for PP, BP and Chla increases when dust was added in three daily doses; however, the maximal values attained were similar in the two treatments. Although the effect was evident in the first osmotrophic level (phytoplankton and bacteria), it was lost further up the food web, masked under the impact of grazing exerted by predators such as heterotrophic flagellates, ciliates and dinoflagellates. This was partly proved by two dilution experiments. This study demonstrates the important role of atmospheric deposition and protist grazing when evaluating the effect on oligotrophic systems characterised by increased numbers of trophic levels.