Seawater carbonate chemistry, nutrients, and Calcidiscus leptoporus (strain RCC1135) growth rate and calcification rate during experiments, 2012@en

The coccolithophore Calcidiscus leptoporus was grown in batch culture under nitrogen (N) as well as phosphorus (P) limitation. Growth rate, particulate inorganic carbon (PIC), particulate organic carbon (POC), particulate organic nitrogen (PON), and particulate organic phosphorus (POP) production were determined and coccolith morphology was analysed. While PON production decreased by 70% under N-limitation and POP production decreased by 65% under P-limitation, growth rate decreased by 33% under N- as well as P-limitation. POC as well as PIC production (calcification rate) increased by 27% relative to the control under P-limitation, and did not change under N-limitation. Coccolith morphology did not change in response to either P or N limitation. While these findings, supported by a literature survey, suggest that coccolith morphogenesis is not hampered by either P or N limitation, calcification rate might be. The latter conclusion is in apparent contradiction to our data. We discuss the reasons for this inference.本研究以颗石藻（coccolithophore）细孔钙盘藻（Calcidiscus leptoporus）为实验材料，将其置于分别受氮（N）限制与磷（P）限制的分批培养环境中进行培养。本研究测定了该藻的生长速率、颗粒无机碳（PIC）、颗粒有机碳（POC）、颗粒有机氮（PON）与颗粒有机磷（POP）的产量，并对其颗石形态开展了分析。研究发现，氮限制条件下颗粒有机氮产量下降70%，磷限制条件下颗粒有机磷产量下降65%；而两种限制条件下，生长速率均下降33%。相较于对照组，磷限制条件下颗粒有机碳与颗粒无机碳（钙化速率）的产量均提升27%，氮限制条件下二者无显著变化。颗石形态在氮或磷限制条件下均未发生改变。尽管结合文献调研得到的上述结果表明，颗石形态发生过程未受氮、磷限制的阻碍，但钙化速率可能受到此类限制的影响。这一结论与本研究获得的实验数据看似矛盾，本文将对该推论的成因展开讨论。