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首页> 外文期刊>Marine biology >Phytoplankton growth and microzooplankton grazing rates in a restricted Mediterranean lagoon (Bizerte Lagoon, Tunisia)
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Phytoplankton growth and microzooplankton grazing rates in a restricted Mediterranean lagoon (Bizerte Lagoon, Tunisia)

机译：在一个受限制的地中海泻湖（突尼斯的比塞大泻湖）中的浮游植物生长和微浮游动物放牧率

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摘要

Phytoplankton growth and microzooplankton grazing were inyestigated in the restricted Bizerte Lagoon in 2002 and 2004. The 2002 study, carried out at one station from January to October, showed significant seasonal variations in phytoplankton dynamics. High growth rates (0.9-1.04 day~(-1)), chlorophyll a (Chl a) concentrations (6.6-6.8 μg l~(-1)) and carbon biomass (392-398 μg C l~(-1)) were recorded in summer (July), when several chain-forming diatoms had intensively proliferated and dominated the carbon biomass (74%). In 2004, four stations were studied during July, a period also characterized by the high proliferation of several diatoms that made up 70% of the algal carbon biomass. In 2004, growth rates (0.34-0.45 day~(-1)) and biomass of algae (2.9-5.4 μg Chl a l~(-1) and 209-260 μg C l~(-1)) were low, which may be related to the lower nutrient concentrations recorded in 2004. Microzooplankton >5 μm were mainly composed of heterotrophic dinoflagellates and ciliates. Microzooplankton biomass peaked during summer (2002 320-329, 2004 246-361 μg C l~(-1)), in response to the enhanced phytoplankton biomass and production. The grazer biomass was dominated by ciliates (71-76%) in July 2002 and by heterotrophic dinoflagellates (52-67%) in July 2004. Throughout the year and at different stations, microzooplankton grazed actively on phytoplankton, removing 26-58% of the Chl a and 57-84% of the primary production. In 2002, the highest grazing impact was observed on the large algae ( >10 μm) during the period of diatom dominance. These results have a significant implication for carbon export to depth. Indeed, the recycling of most of the diatom production by the microbial food web in the upper water column would reduce the flux of material to the seafloor. This should be considered when modeling the carbon cycling in coastal environments and under conditions of diatom dominance. During both studies, ciliates had higher growth rates (0.5-1.5 day~(-1)) and a higher carbon demand (165-470 μg C l~(-1) day~(-1)) than dinoflagellates (0.1-0.5 day~(-1), 33-290 μg C l~(-1) day~(-1)). Moreover, when grazer biomass was dominated by ciliates (in July 2002), herbivory accounted for 71-80% of the C ingested by microzooplankton while it accounted only for 14-23% when dinoflagellates dominated the grazer biomass (in July 2004). These results suggest that, in contrast to findings from open coastal waters, ciliate species of the restricted Bizerte Lagoon were more vigorous grazers of the large algae (diatoms) than were dinoflagellates.
机译：2002年和2004年在受限的比塞大泻湖中对浮游植物的生长和微浮游动物的放牧进行了调查。2002年的研究于1月至10月在一个站进行，显示了浮游植物动力学的明显季节性变化。高生长速率（0.9-1.04天〜（-1）），叶绿素a（Chla）浓度（6.6-6.8μgl〜（-1））和碳生物量（392-398μgC l〜（-1））夏季（7月）记录到了一些碳原子生物量（74％）时，数个成链硅藻大量繁殖并占主导地位。 2004年，在7月对四个站点进行了研究，这一时期的特征还在于构成硅藻生物量70％的几种硅藻的高度增殖。 2004年，藻类的生长速度（0.34-0.45天〜（-1））和藻类生物量（2.9-5.4μgChl al〜（-1）和209-260μgC l〜（-1））较低，可能是与2004年记录的较低的养分含量有关。> 5μm的微浮游生物主要由异养藻鞭毛和纤毛组成。微浮游植物的生物量在夏季达到高峰（2002 320-329，2004 246-361μgC l〜（-1）），这是由于浮游植物生物量和产量增加所致。放牧者的生物量在2002年7月以纤毛虫为主（71-76％），在2004年7月以异养鞭毛藻（52-67％）为主。在全年和不同的站位，微浮游植物在浮游植物上活跃放牧，去除了26-58％的浮游生物。 Chl a和主要产品的57-84％。 2002年，在硅藻主导时期，对大型藻类（> 10μm）的放牧影响最大。这些结果对碳出口到深处具有重要意义。实际上，在上水柱中微生物食物网对大部分硅藻产生物的再循环将减少材料向海底的通量。在模拟沿海环境和硅藻主导条件下的碳循环时，应考虑这一点。在两项研究中，纤毛虫的生长速率（0.5-1.5天〜（-1））和碳需求量（165-470μgC l〜（-1）天〜（-1））均高于鞭毛鞭毛虫（0.1-0.5）。天（-1），33-290μgC l（（-1）天（-1））。此外，当放牧动物的纤毛占优势时（2002年7月），草食动物占微浮游动物摄食碳的71-80％，而当鞭毛藻占优势时，草食动物仅占14-23％（2004年7月）。这些结果表明，与沿海开放水域的发现相反，受限的比塞大泻湖的纤毛虫比大鞭毛藻更有力地捕食大型藻类（硅藻）。

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