Diverse phytoplankton exude polysaccharides that can form a viscous mucus layer surrounding their cells, facilitating complex chemical exchanges with bacteria. An unexplored ramification of mucus production is the influence of its viscosity on the diffusion of nutrients such as vitamins to the cell. Here, I use simulations to demonstrate that mucus viscosity increases the nutrient concentration gradient but always reduces the flux to the cell. Uptake is marginally improved during nutrient pulses, as the mucus acts like a sponge by retaining nutrients near the cell. Lower uptake in the presence of mucus presents a fitness cost that any ecological benefits of mucus must outweigh. I derive a relationship between mucus viscosity and nutrient uptake that can be used to test hypotheses of mutualistic interactions between phytoplankton and bacteria. This work emphasizes the need for empirical measurements of macronutrient diffusion through mucus layers and provides a framework for interpreting those results.

中文翻译：

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浮游植物产生粘液的隐性成本：粘度阻碍养分吸收

多种浮游植物分泌多糖，可在细胞周围形成粘性粘液层，促进与细菌的复杂化学交换。粘液产生的一个未开发的分支是其粘度对营养物质（如维生素）向细胞扩散的影响。在这里，我使用模拟来证明粘液粘度会增加营养浓度梯度，但总是会降低流向细胞的通量。在营养脉冲期间吸收略有改善，因为粘液通过将营养物质保留在细胞附近而起到海绵的作用。在粘液存在的情况下，较低的摄取量会带来健康成本，粘液的任何生态效益都必须超过。我推导出粘液粘度和营养吸收之间的关系，可以用来检验浮游植物和细菌之间互惠相互作用的假设。