Can B-vitamins control phyto-and-bacterioplankton successions in a coastal upwelling region?

b族维生素（硫胺素（B1）、生物素（B7）和钴胺素（B12））是所有生物体用于许多生化反应的有机分子，从DNA和氨基酸合成到二氧化碳同化。尽管它们具有重要的代谢作用，但许多海洋生物不能制造它们，需要从环境中获取它们。由于不同生物对特定维生素的需求不同，藻类种类组成的变化可以用它们对b族维生素的不同需求来解释。例如，藻华期间水体生物特性的变化（所需维生素的去除和其他维生素的释放）可能有利于需要前一次藻华释放的维生素的藻类（建立植物演替）。这种对水的选择性预处理可能是藻类物种季节性演替的一个因素。然而，评估维生素在海洋生态中的作用一直很困难。迄今为止，还没有一项研究能够全面地估计维生素在初级生产力和物种演替中的重要性。在沿海上升流地区尤其如此，尽管面积相对较小，但其生产力却比开阔海域的相应区域高几个数量级。事实上，这些区域贡献了世界渔业的很大一部分。因此，为了试图预测由于人类活动而导致的世界海洋未来的变化，需要确定影响或控制在上升流地区非常多产的食物链中占主导地位的藻类群落的变量。本科和研究生教育将通过积极参与联合实验室实验和实地考察而进一步发展。该项目将支持一名研究生的论文工作。这项研究将调查b族维生素的可用性如何影响南加州上升流地区沿海水域藻类和浮游细菌种群增长的动态。这项全面的实地调查将在洛杉矶附近的圣佩德罗盆地内的一个长期时间序列站确定几种溶解和微粒b族维生素、无机微量和大量营养素的就地时间浓度，同时确定浮游植物和细菌丰度以及物种组成的季节性变化。除了这些测量外，还将对天然浮游生物组合进行实地孵化实验，以研究有机和无机营养修正对浮游植物和细菌群落结构的影响。这项研究将首次确定，在高产的沿海上升流地区，环境b族维生素的可用性影响藻类和细菌物种的演替，并且多种和不同的b族维生素需求限制了这些地区某些浮游植物物种的生长。此外，本研究将试图表明，沿海上升流将一些b族维生素从中上层受细菌影响的水源水输送到光带的浮游植物群落。

B-vitamins (thiamin (B1), biotin (B7), and cobalamin (B12)) are organic molecules used by all organisms for many biochemical reactions ranging from DNA and amino acid synthesis to carbon dioxide assimilation. Despite their metabolic importance, many marine organisms cannot make them and need to obtain them from the environment. Because the requirement for a specific vitamin is different for different organisms, changes in the species composition of algae could be explained by their different B-vitamin requirements. For example, changes in the biological properties of waters during an algal bloom (removal of needed vitamins and release of other vitamins) may favor algae that require the vitamin released by the previous bloom (setting up a floral succession). This selective preconditioning of the waters may be one factor in the seasonal succession of algal species. However, evaluating the role of vitamins in marine ecology has been difficult. No study to date has been comprehensive enough to estimate the importance of vitamins in primary productivity and species succession. This is especially true in coastal upwelling regions that although relatively small in area, are orders of magnitude more productive than their open-ocean counterparts. In fact, those regions contribute a significant portion of the world fisheries. Therefore, in order to try to predict future changes in the world ocean due to human activity, the variables that influence or control the algal communities that dominate the very productive food chains of upwelling regions need to be identified. Undergraduate and graduate education will be furthered through active participation in the joint laboratory experiments and fieldwork. This project will support the dissertation work of one graduate student.This study will investigate how the availability of B-vitamins affects the dynamics of algal- and bacterioplankton population growth in coastal waters of an upwelling region off Southern California. This comprehensive field investigation will determine in situ temporal concentrations of several dissolved and particulate B-vitamins, inorganic micro- and macronutrients, concurrently with seasonal changes in phytoplankton and bacterial abundances and species composition at a long-term time series station within the San Pedro Basin near Los Angeles. Those measurements will be complemented with field incubation experiments with natural plankton assemblages to study the effect of organic and inorganic nutrient amendments on phytoplankton and bacterial community structure. This study will establish for the first time that the availability of ambient B-vitamins influence algal and bacterial species succession in a highly productive coastal upwelling region and that multiple and differing B-vitamin requirements limit growth of some phytoplankton species in those areas. Furthermore, this study will try to show that coastal upwelling transports some B-vitamins to the phytoplankton community in the photic zone from bacterially-influenced source waters within the upper mesopelagic zone.