Data from: CO2 alters community composition and response to nutrient enrichment of freshwater phytoplankton

Nutrients can limit the productivity of ecosystems and control the composition of the communities of organisms that inhabit them. Humans are causing atmospheric CO2 concentrations to reach levels higher than those of the past millions of years while at the same time propagating eutrophication through the addition of nutrients to lakes and rivers. We studied the effect of elevated CO2 concentrations, nutrient addition and their interaction in a series of freshwater mesocosm experiments using a factorial design. Our results highlight the important role of CO2 in shaping phytoplankton communities and their response to nutrient addition. We found that CO2 greatly magnified the increase in phytoplankton growth caused by the increased availability of nutrients. Elevated CO2 also caused changes in phytoplankton community composition. As predicted from physiology and laboratory experiments, the taxonomic group that was most limited by current day CO2 concentrations, chlorophytes, increased in relative frequency at elevated CO2. This predictable change in community composition with changes in CO2 is not altered by changes in the availability of other nutrients.

营养盐可限制生态系统生产力，并调控栖息其中的生物群落组成。当前人类活动使大气二氧化碳（CO2）浓度达到数百万年来未有的高位，同时通过向湖泊与河流输入营养盐加剧了水体富营养化。本研究采用析因实验设计，通过一系列淡水中宇宙（mesocosm）实验，探究了高浓度CO2、营养盐添加及其交互作用的效应。研究结果凸显了CO2在塑造浮游植物群落及其对营养盐添加响应过程中的关键作用。我们发现，CO2可显著放大因营养盐可利用性提升所带来的浮游植物生长增幅。高浓度CO2同时还会改变浮游植物群落的组成结构。正如生理学与室内实验所预测的那样，在当前CO2浓度下受限制程度最高的分类群——绿藻门（chlorophytes），在高CO2环境下的相对丰度显著提升。这种随CO2浓度变化而产生的群落组成可预测变化，并不会因其他营养盐的可利用性改变而发生改变。