Collaborative Research: A Critical Examination of the Relationship Between Marine Phytoplankton Growth Rates and Phosphate Concentrations: Monod or Not

本项目利用放射性磷(~(33)P)作为示踪剂，在恒化器实验中研究海洋浮游植物单种培养中磷浓度与生长速率的关系。几十年来，这种关系一直被认为是由莫诺方程描述的，但比色法无法准确测量磷酸盐的生长速度限制浓度，这排除了对这一假设的严格测试。理论分析表明，与Monod方程的发散可能与限制生长速率的衬底通过细胞周围的边界层扩散有关。由于限制养分的细胞定额对磷的变化比对氮的影响更大，因此可以表明，通过边界层扩散对生长速率曲线形状的影响，磷可能比氮大得多。这项拟议工作的智力价值在于使用33P的示踪剂来准确测量纳摩尔浓度范围内的磷酸盐，并使用化学稳定剂来提供严格的生长速度控制。到目前为止，这些方法的结合提供了最好的机会来定义磷酸盐浓度和增长率之间的关系，从而最终提供了对Monod增长模型的严格测试。拟议工作的更广泛影响包括，这项研究将是路易斯安那州立大学(LSU)和夏威夷大学(UH)的合作努力，并将为每个机构的一名研究生提供支持。路易斯安那州立大学和密歇根大学都是EPSCoR机构。劳斯博士编写了一本名为《海洋学家的数学方法》的教科书(约翰·威利)，并在路易斯安那州立大学教授一门研究生课程，该课程利用了这本书。课程和课文包括有关建模的材料。拟议工作的结果将被整合到劳博士的课程和他的书的未来版本中，并将提交科学文献发表。然而，拟议工作的最广泛影响将是我们对控制磷限制系统中浮游植物生长速度的关系的理解，以及藻类之间资源竞争的结果。几十年来，这种关系一直被认为是莫诺方程。这个项目将使用现有的工具来确定它是还是不是。

This project involves the use radioactive phosphorus (33P) as a tracer in chemostat experiments to study the relationship between phosphate concentrations and growth rate in monospecific cultures of marine phytoplankton. For literally decades that relationship has been assumed to be described by the Monod equation, but the inability of colorimetric methods to accurately measure growth-rate-limiting concentrations of phosphate has precluded a rigorous test of this hypothesis. Theoretical analysis indicates that divergence from the Monod equation may be associated with diffusion of the growth-rate-limiting substrate through the boundary layer around the cell. Because the cell quota of limiting nutrient is more variable for phosphorus than nitrogen, it can be shown that the impact of diffusion through the boundary layer on the shape of the growth rate curve is likely to be much greater for phosphorus than for nitrogen. The intellectual merit of the proposed work lies in the use of tracer amounts of 33P to accurately measure phosphate in the nanomolar concentration range and the use of chemostats to provide rigorous control of growth rates. The combination of these methodologies offers by far the best chance of defining the relationship between phosphate concentration and growth rate and hence at last provide a rigorous test of the Monod growth model.The broader impacts of the proposed work include the fact that the research will be a collaborative effort between Louisiana State University (LSU) and the University of Hawaii (UH) and will provide support for a graduate student at each institution. Both LSU and UH are EPSCoR institutions. Dr. Laws has written a textbook titled Mathematical Methods for Oceanographers (John Wiley) and teaches a graduate course at LSU that makes use of that text. The course and text include material on modeling. The results of the proposed work will be integrated into Dr. Laws' course and into future editions of his book and will be submitted for publication in the scientific literature. The broadest impact of the proposed work, however, will be on our understanding of the relationship that controls phytoplankton growth rates in phosphorus-limited systems and the outcome of resource competition among algae. For literally decades that relationship has been assumed to be the Monod equation. This project will use existing the tools to determine whether it is or is not.