Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA.
Marine Science Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
Environ Microbiol. 2018 Nov;20(11):4184-4193. doi: 10.1111/1462-2920.14431. Epub 2018 Oct 22.
A mix of adaptive strategies enable diatoms to sustain rapid growth in dynamic ocean regions, making diatoms one of the most productive primary producers in the world. We illustrate one such strategy off coastal California that facilitates continued, high, cell division rates despite silicic acid stress. Using a fluorescent dye to measure single-cell diatom silica production rates, silicification (silica per unit area) and growth rates we show diatoms decrease silicification and maintain growth rate when silicon concentration limits silica production rates. While this physiological response to silicon stress was similar across taxa, in situ silicic acid concentration limited silica production rates by varying degrees for taxa within the same community. Despite this variability among taxa, silicon stress did not alter the contribution of specific taxa to total community silica production or to community composition. Maintenance of division rate at the expense of frustule thickness decreases cell density which could affect regional biogeochemical cycles. The reduction in frustule silicification also creates an ecological tradeoff: thinner frustules increase susceptibility to predation but reducing Si quotas maximizes cell abundance for a given pulse of silicic acid, thereby favouring a larger eventual population size which facilitates diatom persistence in habitats with pulsed resource supplies.
多种适应性策略使硅藻能够在动态海洋区域维持快速生长，使硅藻成为世界上最具生产力的初级生产者之一。我们展示了加利福尼亚沿海的一种这样的策略，即使在硅酸胁迫下，该策略也能促进持续的、高的细胞分裂率。我们使用荧光染料来测量单细胞硅藻硅的生产率、硅化（单位面积的硅）和生长速率，结果表明，当硅浓度限制硅生产率时，硅藻会降低硅化作用并保持生长速率。虽然这种对硅胁迫的生理反应在不同分类群中相似，但同一群落内的分类群之间的原位硅酸浓度对硅的生产率的限制程度不同。尽管分类群之间存在这种可变性，但硅胁迫并没有改变特定分类群对总群落硅产量或群落组成的贡献。以牺牲壳层厚度为代价维持分裂率会降低细胞密度，这可能会影响区域生物地球化学循环。硅化作用减少也会产生生态权衡：较薄的壳层会增加被捕食的易感性，但减少硅配额可以使给定的硅酸脉冲下的细胞丰度最大化，从而有利于更大的最终种群规模，从而有利于在脉冲资源供应的栖息地中硅藻的生存。
