Diatoms rapidly alter sinking behavior in response to changing nutrient concentrations
Diatoms rapidly alter sinking behavior in response to changing nutrient concentrations
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DOI：
10.1002/lno.11649
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发表时间：
2020-11-27
影响因子：
4.5
通讯作者：
Gemmell, Brad J.
中科院分区：
文献类型：
--
作者：
Du Clos, Kevin T.;Karp-Boss, Lee;Gemmell, Brad J.
硅藻的下沉速度影响其在水柱中的深度，这决定了它获得光线和营养物质的能力。一些大型的中心硅藻物种执行不稳定的下沉行为，其中细胞的下沉速度在秒的时间尺度上振荡超过一个数量级。已知硅藻在暴露于营养物充足的条件下数小时至数天后会降低平均下沉速度和不稳定下沉的幅度。在这里，我们表明，在较短的时间尺度分钟到小时，营养剥夺圆筛藻细胞增加的平均值和不稳定性时，暴露于增加营养浓度的下沉。培养物暴露于硝酸盐或硅酸盐耗尽的培养基，随后缺失营养素的尖峰显示出在前2小时内下沉速度增加，在接下来的22小时内下降。磷酸盐剥夺培养物对磷酸盐加标没有类似的反应。在一个实验中，与人工nutricline中，细胞遇到了急剧增加的营养浓度超过10厘米的距离，平均下沉速度增加了8倍，下沉不稳定性显着增加，这些下沉速度的变化发生在33分钟。对比短期和长期的下沉行为的反应，在这项研究中看到的证明了检查下沉行为在多个时间尺度的重要性。最初的快速和不稳定的下沉后，遇到营养浓度的增加，可能有助于硅藻利用不均匀的营养分布。长期、缓慢和稳定的下沉可能有利于最大限度地增加曝光量和最小化来自不稳定下沉的能量成本。
A diatom's sinking speed affects its depth in the water column, which determines its access to light and nutrients. Some large, centric diatom species perform an unsteady sinking behavior in which a cell's sinking speed oscillates over more than an order of magnitude on time scales of seconds. Diatoms are known to decrease mean sinking speeds and the magnitude of unsteady sinking following exposure to nutrient replete conditions over hours to days. Here we show that on shorter time scales of minutes to hours, nutrient deprived Coscinodiscus wailesii cells increase the mean and unsteadiness of their sinking when exposed to increased nutrient concentrations. Cultures exposed to nitrate or silicate-depleted media followed by a spike of the missing nutrient showed a sinking speed increase within the first 2 h that declined over the next 22 h. Phosphate deprived cultures did not respond similarly to a phosphate spike. In an experiment with an artificial nutricline in which cells encountered a sharp increase in nutrient concentrations over a distance of 10 cm, mean sinking speeds increased eight fold, and sinking unsteadiness increased significantly; these sinking speed changes occurred over 33 min. The contrasting short and long-term sinking behavior responses seen in this study demonstrates the importance of examining sinking behavior over multiple time scales. Initial fast and unsteady sinking upon encountering increasing nutrient concentrations may help diatoms take advantage of patchy nutrient distributions. Longer term, slow and steady sinking may be beneficial for maximizing light exposure and minimizing energy costs from unsteady sinking.