Abstract The color of many lakes and seas is changing, which is likely to affect the species composition of freshwater and marine phytoplankton communities. For example, cyanobacteria with phycobilisomes as light‐harvesting antennae can effectively utilize green or orange‐red light. However, recent studies show that they use blue light much less efficiently than phytoplankton species with chlorophyll‐based light‐harvesting complexes, even though both phytoplankton groups may absorb blue light to a similar extent. Can we advance ecological theory to predict how these differences in light‐harvesting strategy affect competition between phytoplankton species? Here, we develop a new resource competition model in which the absorption and utilization efficiency of different colors of light are varied independently. The model was parameterized using monoculture experiments with a freshwater cyanobacterium and green alga, as representatives of phytoplankton with phycobilisome‐based vs. chlorophyll‐based light‐harvesting antennae. The parameterized model was subsequently tested in a series of competition experiments. In agreement with the model predictions, the green alga won the competition in blue light whereas the cyanobacterium won in red light, irrespective of the initial relative abundances of the species. These results are in line with observed changes in phytoplankton community structure in response to lake brownification. Similarly, in marine waters, the model predicts dominance of Prochlorococcus with chlorophyll‐based light‐harvesting complexes in blue light but dominance of Synechococcus with phycobilisomes in green light, with a broad range of coexistence in between. These predictions agree well with the known biogeographical distributions of these two highly abundant marine taxa. Our results offer a novel trait‐based approach to understand and predict competition between phytoplankton species with different photosynthetic pigments and light‐harvesting strategies.

中文翻译：

---

不同光捕获策略下浮游植物物种之间的水色变化竞争


摘要 许多湖泊和海洋的颜色正在发生变化，这很可能影响淡水和海洋浮游植物群落的物种组成。例如，以藻胆体作为光捕获天线的蓝细菌可以有效地利用绿光或橙红光。然而，最近的研究表明，它们使用蓝光的效率远低于具有基于叶绿素的光捕获复合物的浮游植物物种，尽管这两个浮游植物群可能吸收蓝光的程度相似。我们能否推进生态理论来预测这些光捕获策略的差异如何影响浮游植物物种之间的竞争？在这里，我们开发了一种新的资源竞争模型，其中不同颜色的光的吸收和利用效率独立变化。该模型使用淡水蓝藻和绿藻的单一培养实验进行参数化，作为浮游植物的代表，具有基于藻胆体和基于叶绿素的光捕获天线。随后在一系列竞争实验中测试了参数化模型。与模型预测一致，绿藻在蓝光下赢得了竞争，而蓝藻在红光下获胜，无论该物种的初始相对丰度如何。这些结果与观察到的浮游植物群落结构因湖泊褐化而发生的变化一致。同样，在海水中，该模型预测在蓝光下具有基于叶绿素的光捕获复合物的原绿球藻占主导地位，但在绿光下具有藻胆体的聚球藻占主导地位，并且两者之间存在广泛的共存。 这些预测与这两个高度丰富的海洋类群的已知生物地理分布非常吻合。我们的结果提供了一种基于性状的新颖方法来理解和预测具有不同光合色素和光捕获策略的浮游植物物种之间的竞争。