Dhib Amel, Denis Michel, Ziadi Boutheina, Barani Aude, Turki Souad, Aleya Lotfi
Laboratoire de Chrono-Environnement, UMR CNRS 6249, Université de Franche-Comté, Besancon, France.
Laboratoire Milieu Marin, Institut National des Sciences et Technologies de la Mer (INSTM), Centre la Goulette, la Goulette, Tunisia.
Environ Sci Pollut Res Int. 2017 May;24(15):13710-13721. doi: 10.1007/s11356-017-8939-z. Epub 2017 Apr 10.
In the eutrophic Ghar El Melh Lagoon (GML, Tunisia), the distribution of heterotrophic prokaryotes, pico- and nanophytoplankton was studied at five stations in November 2012 at the single cell level, along with environmental factors. Flow cytometry analysis of ultraplankton (<10 μm) resolved (i) two heterotrophic prokaryote groups, low and high nucleic acid contents (LNA and HNA, respectively), and (ii) eight to nine ultraphytoplankton groups (cryptophyte-like cells, two nanoeukaryote subgroups, two picoeukaryote subgroups and three Synechococcus-like cells subgroups). Prochlorococcus was not detected. According to redundancy analysis (RDA), a significant difference was found in the distribution of the ultraplankton between stations (F = 2.61, p < 0.05); maximum proliferations of heterotrophic prokaryotes were observed in the inner parts of the lagoon at stations 3, 4 and 5 affected by urban, agricultural and industrial discharges. Ultraphytoplankton concentrations were the highest near the outlet of the lagoon at stations 1 and 2 influenced by freshwater outflow and oligotrophic Mediterranean water inflow, respectively. At station 1, the large ultraphytoplankton concentration derives from the high abundance of cryptophyte-like cells favoured by the freshwater outflow whereas at station 2, the input of oligotrophic Mediterranean water enhanced the abundance of Synechococcus and picoeukaryotes at the expense of nanoeukaryotes. Two trophic regimes were thus differentiated in GML.
在富营养化的加赫尔梅尔赫泻湖（突尼斯加赫尔梅尔赫泻湖），2012年11月在五个站点对异养原核生物、微微型和微型浮游植物的分布进行了单细胞水平的研究，并分析了环境因素。对超浮游生物（<10μm）的流式细胞术分析分辨出：（i）两个异养原核生物组，即低核酸含量组和高核酸含量组（分别为LNA和HNA）；（ii）八到九个超浮游植物组（隐藻样细胞、两个微型真核生物亚组、两个微微型真核生物亚组和三个聚球藻样细胞亚组）。未检测到原绿球藻。根据冗余分析（RDA），各站点间超浮游生物的分布存在显著差异（F = 2.61，p < 0.05）；在受城市、农业和工业排放影响的泻湖内部3号、4号和5号站点观察到异养原核生物的最大增殖。超浮游植物浓度在泻湖出口附近最高，1号站点受淡水流出影响，2号站点受贫营养地中海海水流入影响。在1号站点，大量的超浮游植物浓度源于淡水流出有利于隐藻样细胞的高丰度，而在2号站点，贫营养地中海海水的输入增加了聚球藻和微微型真核生物的丰度，代价是微型真核生物。因此，加赫尔梅尔赫泻湖区分出了两种营养状态。
