Environmental drivers of mixotrophy and its impact on the plankton metabolic balance

混合营养是一种成功的营养策略，因为它为海洋微生物提供了结合光自养和吞噬异养的能力，因此可以使用其他形式的碳吸收(1)。因此，混合营养体含有一个功能性的叶绿体，并可以额外地以猎物为食以获取碳。这种替代的营养途径在光照和营养有限的环境下是有利的，在这种环境下，混合营养体与严格的自养或异养生物相比具有营养优势(2)。关于混合营养对叶绿素-a与初级生产之间的关系、对净群落生产的影响，以及对向更高营养水平的碳转移和生态系统功能的影响，目前的认识有限。最近在温带沿海水域进行的一项研究表明，混合营养可以改变初级产量估算与叶绿素- A浓度之间的关系，这种变化可能会给卫星和滑翔机的初级产量估算带来偏差(3)。然而，目前还没有量化这种关系的可变性，以及不同的生物（噬菌体、混合营养纤毛虫和球石藻）是否相似，或者环境条件的影响。本项目将结合实验室工作和数值模型来解决这些问题。

Mixotrophy is a successful nutritional strategy as it provides marine micro-organisms with the ability to combine photoautotrophy and phago-heterotrophy, and therefore use alternative forms of carbon uptake (1). Thus, mixotrophs contain a functional chloroplast and can additionally graze on prey to obtain their carbon. This alternative nutritional pathway is advantageous under light- and nutrient-limited environments, where mixotrophs get a nutritional advantage compared to strict autotrophs or heterotrophs (2). There is limited knowledge on the influence of mixotrophy on the relationships between chlorophyll-a and primary production, on the net community production, and therefore, on the carbon transfer to higher trophic levels and the ecosystem functioning. A recent study in temperate coastal waters showed that mixotrophy can alter the relationship between primary production estimates and chlorophyll-a concentration, and this change could introduce biases to the primary production estimations from satellites and gliders (3). However, there is currently no quantification of the variability of this relationship, and whether it is similar for different organisms (bacteriophages, mixotrophic ciliates and coccolithophores) or the influence of environmental conditions. This project will address these questions combining laboratory work and numerical models.