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首页> 外文期刊>Journal of Experimental Marine Biology and Ecology >Influence of fluctuating irradiance on photosynthesis, growth and community structure of estuarine phytoplankton under increased nutrients and acidification
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Influence of fluctuating irradiance on photosynthesis, growth and community structure of estuarine phytoplankton under increased nutrients and acidification

机译：养分增加和酸化条件下辐照度变化对河口浮游植物光合作用，生长和群落结构的影响

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Estuaries represent the interface between riverine and marine ecosystems and they are among the most productive areas on Earth; thus it is of utmost importance to understand their functioning in a global change scenario. So far, it is virtually unknown how the interaction between nutrient inputs, acidification and fluctuating light regimes could alter photosynthesis, growth, and phytoplankton structure in the end members (i.e., river and sea) of estuaries. Using the Chubut river estuary (Argentina) as a model ecosystem, we conducted experimentation during the austral summer (i.e., the windy season, February of 2016) with both, river and seawater phytoplankton communities to assess these topics. We evaluated the impact of fluctuating irradiance (static vs. mixed conditions) using short- ( < one day) and mid-term acclimation (five days) and mimicking scenarios of higher acidification and nutrients (Future) as compared with an unmodified Present. The growth of both communities increased significantly under the Future as compared to the Present scenario, but mixing decreased growth only in seawater phytoplankton. Small centric diatoms (mainly Thalassiosira spp.) co-dominated with unidentified flagellates in the seawater, but the relative abundance of diatoms was higher in the Future as compared with the Present scenario. Diatoms and cryptophytes co-dominated in the river at the end of the experiments for both static and mixed conditions. Net primary productivity (NPP) decreased in the Future scenario and this was coupled with higher inhibition (k) of photosystem II (PSII), in both communities. Our results indicate that fluctuating irradiance, under a future global change scenario, as simulated here, has a significant impact on the structure and growth of seawater phytoplankton, together with increases in photochemical inhibition and decreases in NPP. However, these changes are much smaller in the river phytoplankton. Thus, the overall effects of mixing on the trophodynamics of the area will be more important at the sea than in the river end of the estuary.
机译：河口代表着河流与海洋生态系统之间的界面，是地球上生产力最高的地区之一。因此，最重要的是了解它们在全球变化情况下的功能。到目前为止，实际上还不清楚养分输入，酸化和波动的光照状态之间的相互作用如何改变河口末端成员（即河和海）的光合作用，生长和浮游植物的结构。我们使用丘布特河河口（阿根廷）作为模型生态系统，在南方夏季（即2016年2月的大风季节）进行了河流和海水浮游植物群落的实验，以评估这些主题。我们使用短期（<一天）和中期适应（五天）以及模拟较高酸化和营养素（未来）的情景（与未修改的Present）相比，评估了辐照度波动（静态与混合条件）的影响。与目前的情况相比，在未来情况下，两个社区的增长均显着增加，但混合情况仅在海水浮游植物中下降。较小的中心硅藻（主要为Thalassiosira spp。）与海水中未识别的鞭毛虫共同控制，但与当前情景相比，未来硅藻的相对丰度更高。在静态和混合条件下，实验结束时，河中的硅藻和隐生植物共占主导地位。未来情景中的净初级生产力（NPP）下降，这与两个社区对光系统II（PSII）的较高抑制（k）相结合。我们的结果表明，在此模拟的未来全球变化情况下，辐照度波动会对海水浮游植物的结构和生长产生重大影响，同时还会增加光化学抑制作用并降低NPP。然而，这些变化在浮游植物河中要小得多。因此，混合对区域的营养动力学的总体影响在海上比在河口的河岸更重要。

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