Sr in coccoliths of Scyphosphaera apsteinii: Partitioning behavior and role in coccolith morphogenesis
Sr in coccoliths of Scyphosphaera apsteinii: Partitioning behavior and role in coccolith morphogenesis
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DOI：
10.1016/j.gca.2020.06.023
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发表时间：
2020-09
影响因子：
5
通讯作者：
Erin M. Meyer;G. Langer;C. Brownlee;Glen L. Wheeler;Alison R. Taylor
中科院分区：
文献类型：
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作者：
Erin M. Meyer;G. Langer;C. Brownlee;Glen L. Wheeler;Alison R. Taylor
颗石藻是全球碳酸钙的重要贡献者，通过其物种特异性生产方解石颗石。通过同位素和微量元素（包括Sr）的地球化学分析，纳米化石颗石方解石仍然是古重建的重要工具，Sr是过去海洋表面温度和生产力的潜在指标。（Zygodiscales）表现出异常高的Sr/Ca比值和相应的高分配系数（DSr= 2.5）在他们的两个形态不同类型的球石：扁平muroliths和桶状lopadoliths。这是否反映了与其他颗石藻相比钙化的机制差异尚不清楚。因此，我们研究了Sr在S. apsteinialcification的可能作用，通过生长细胞在耗尽（0.33 mmol/mol Sr/Ca），环境（9 mmol/mol Sr/Ca），和高于环境Sr条件（36和72 mmol/mol Sr/Ca）。对生长、光系统II的量子效率（Fv/Fm）、颗石形态和方解石DSr的影响进行了评价。对S无影响。当Sr/Ca为0.33-36 mmol/mol时，细胞生长速率或Fv/Fm为apsteinigrowthrate。然而，在72 mmol/mol Sr/Ca的生长速率显着降低，虽然Fv/Fm不受影响。从环境（9 mmol/mol）减少Sr/Ca并没有显着改变畸形和异常的muroliths和lopadoliths的频率，但在高于环境Sr/Ca的条件下，颗石形态显着中断。这意味着，锶不是一个重要的决定因素，在正常的颗石方解石形态在这个二形物种。使用能量色散谱（EDS），我们观察到增加[Sr]和减少DSr的cocoliths的Sr/Ca的增长培养基中增加。有趣的是，Muroliths有显着较低的Sr/Ca比lopadoliths在环境和升高[Sr]，和lopadoliths提示有较低的Sr比在环境条件下的基地。综上所述，S. apsteiniis不同于其他颗石藻，因为异常高的DSrand内部和颗石的Sr/Ca的变化。这些观察结果可以解释的机械差异的选择性的Ca 2+运输途径或锶和钙结合能力的有机成分，如多糖与颗石生成。
Coccolithophores are important contributors to global calcium carbonate through their species-specific production of calcite coccoliths. Nannofossil coccolith calcite remains an important tool for paleoreconstructions through geochemical analysis of isotopic and trace element incorporation including Sr, which is a potential indicator of past surface ocean temperature and productivity.Scyphosphaera apsteinii(Zygodiscales) exhibits an unusually high Sr/Ca ratio and correspondingly high partitioning coefficient (DSr= 2.5) in their two morphologically distinct types of coccoliths: flat muroliths and barrel-like lopadoliths. Whether or not this reflects mechanistic differences in calcification compared to other coccolithophores is unknown. We therefore examined the possible role of Sr inS. apsteiniicalcification by growing cells in deplete (0.33 mmol/mol Sr/Ca), ambient (9 mmol/mol Sr/Ca), and higher than ambient Sr conditions (36 and 72 mmol/mol Sr/Ca). The effects on growth, quantum efficiency of photosystem II (Fv/Fm), coccolith morphology, and calcite DSrwere evaluated. No effect onS. apsteiniigrowth rate or Fv/Fmwas observed when cells were grown in Sr/Ca between 0.33–36 mmol/mol. However, at 72 mmol/mol Sr/Ca growth rate was significantly reduced, although Fv/Fmwas unaffected. Reducing the Sr/Ca from ambient (9 mmol/mol) did not significantly alter the frequency of malformed and aberrant muroliths and lopadoliths, but at higher than ambient Sr/Ca conditions coccolith morphology was significantly disrupted. This implies that Sr is not a critical determining factor in normal coccolith calcite morphology in this dimorphic species. Using energy dispersive spectroscopy (EDS) we observed an increase in [Sr] and decrease in DSrof coccoliths as the Sr/Ca of the growth medium increased. Interestingly, muroliths had significantly lower Sr/Ca than lopadoliths at ambient and elevated [Sr], and lopadolith tips had lower Sr than bases in ambient conditions. In summary, the Sr fractionation behavior ofS. apsteiniiis distinct from other coccolithophores because of an unusually high DSrand inter- and intra-coccolith variability in Sr/Ca. These observations could be explained by mechanistic differences in the selectivity of the Ca2+transport pathway or in the Sr-and Ca-binding capacity of organic components, such as polysaccharides associated with coccolithogenesis.