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首页> 外文期刊>Hydrobiologia >Identification of factors constraining nitrate assimilation in lake Superior, Laurentian Great Lakes.
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Identification of factors constraining nitrate assimilation in lake Superior, Laurentian Great Lakes.

机译：确定限制劳伦式大湖苏必利尔湖中硝酸盐同化的因素。

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Despite a well-documented rise in nitrate concentration over the past century, Lake Superior has retained an oligotrophic character. In part, this status results from physical attributes of the lake including low temperatures and prolonged isothermy, resulting in deep-mixing and light limitation which constrain primary production. Lake Superior is also phosphorus deficient which limits phytoplankton growth. We conducted large (20 l) volume factorial bioassay experiments to assess the influence of light and nutrients (P, Fe) on nitrate assimilation by a Lake Superior chlorophyte alga. Bioassays seeded with the chlorophyte yielded a strong response to light resulting in the rapid depletion of nitrate. High light resulted in higher activities of the key N-assimilation enzyme nitrate reductase (NR) and increased algal biomass compared to low light treatments. NR activity was highly correlated with rates of nitrate incorporation in bioassays and field surveys suggesting that NR occupies a critical place in nitrate metabolism. In bioassays, the addition of nutrients (P, Fe) only slightly increased the rate at which nitrate became depleted. Parallel trials using a luminescent cyanobacterial bioreporter confirmed the lack of response by added nutrients supporting light as an important factor in constraining nitrate assimilation by phytoplankton in the lake.
机译：尽管在过去的一个世纪中，硝酸盐浓度有大量文献记载，但苏必利尔湖仍保留了贫营养特征。这种状态部分是由于湖泊的物理属性（包括低温和等温线延长）导致的，导致深度混合和光照受限，从而限制了初级生产。苏必利尔湖还缺乏磷，限制了浮游植物的生长。我们进行了大体积（20升）的析因生物测定实验，以评估光和养分（P，Fe）对苏必利尔湖水生植物藻类吸收硝酸盐的影响。接种了绿藻植物的生物测定法对光产生强烈反应，从而导致硝酸盐的快速消耗。与弱光处理相比，强光导致关键的N-同化酶硝酸还原酶（NR）的活性更高，藻类生物量增加。在生物测定和田间调查中，NR的活性与硝酸盐的掺入率高度相关，这表明NR在硝酸盐代谢中占据着至关重要的位置。在生物测定中，添加营养素（P，Fe）仅会稍微增加硝酸盐的消耗速度。使用发光蓝细菌生物报告器的平行试验证实，添加支持光的养分缺乏反应，这是限制湖泊中浮游植物对硝酸盐同化的重要因素。

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