Rapid climate changes may potentially have strong impacts on the ecosystem structure and nutrient dynamics of lakes as well as implications for water quality. We used a space-for-time approach to elucidate such possible effects by comparing data from 1656 shallow lakes (mean depth <3 m) in north temperate Denmark (DK) and subtropical Florida (FL). The lakes were categorized into 7 total phosphorus (TP) classes within the range of 2 to 300 µg L⁻¹. Physicochemical variables showed significant seasonal differences, which can be attributed to different sunlight regimes and temperatures. The FL lakes had overall higher fish biomasses (notably in the littoral zone) but a substantially lower zooplankton biomass and body mass of microcrustaceans, a much lower zooplankton:phytoplankton biomass ratio (lower grazing on phytoplankton), and a markedly lower biomass of benthic invertebrates, indicating much greater control of consumers by fish in the FL lakes. Accordingly, the summer phytoplankton biomass was higher in the FL lakes. Cyanobacteria in summer were proportionally more important in the FL lakes at all TP levels, whereas the proportion of dinophytes, chrysophytes, and cryptophytes was higher in the DK lakes at low TP. Submerged macrophytes occurred at higher TP (>100 µg L⁻¹) in the FL lakes, but coverage was higher in the DK lakes at low TP. We also found lower oxygen saturation in the nutrient-rich FL lakes than in the DK lakes, suggesting lower net ecosystem production in the FL lakes. We discuss our results within the framework of climate warming.

快速的气候变化可能对湖泊的生态系统结构和养分动态以及水质产生重大影响。通过比较北温带丹麦（DK）和亚热带佛罗里达（FL）的1656个浅湖（平均深度<3 m）的数据，我们使用了一种时空方法来阐明这种可能的影响。湖泊分为2级至300 µg L ^-1范围内的7种总磷（TP）类。理化变量显示出明显的季节性差异，这可以归因于不同的日照制度和温度。FL湖的鱼类生物量总体较高（特别是在沿海地区），但浮游动物的生物量和微甲壳类的生物量却要低得多，浮游动物与浮游植物的生物量比要低得多（浮游植物的放牧率较低），底栖无脊椎动物的生物量明显较低。 ，表明佛罗里达州湖泊对鱼类的消费者控制更大。因此，佛罗里达湖的夏季浮游植物生物量较高。在所有TP水平下，夏季蓝藻在FL湖泊中的比例成正比，而在TP低的DK湖泊中，藻类，温藻和隐生植物的比例更高。淹没的植物在较高的TP（> 100 µg L^-1）在FL湖中，但在TP较低时DK湖中的覆盖率更高。我们还发现，营养丰富的FL湖泊中的氧饱和度低于DK湖泊，这表明FL湖泊中的净生态系统产量较低。我们在气候变暖的框架内讨论我们的结果。