Global increases in atmospheric CO₂ and temperatures will impact aquatic systems, with freshwater habitats being affected. Some studies suggest that these conditions will promote cyanobacterial dominance. There is a need for a clearer picture of how algal species and strains within species will respond to higher temperatures and CO₂, especially in combination. This study examined two chlorophytes (Monoraphidium and Staurastrum), and two strains of the cyanobacterium Raphidiopsis raciborskii (straight S07 and coiled C03), to determine how the combination of higher temperature and CO₂ levels will affect their growth and maximum cell concentrations. Continuous cultures were used to compare the steady state cell concentrations at 28 °C and 30 °C, and CO₂ partial pressures (pCO₂), 400 and 750 ppm for all cultures, and in addition 1000 ppm at 28 °C for R. raciborskii strains. This study showed that, for all species, water temperature had a greater effect than higher pCO₂ on cell concentrations. There were clear differences in response between the chlorophyte species, with Monoraphidium preferring 28 °C and Staurastrum preferring 30 °C. There were also differences in response of the R. raciborskii strains to increasing temperature and pCO₂, with S07 having a greater increase in cell concentration. Genome analysis of R. raciborskii showed that the straight strain has five additional carbon acquisition genes (β-CA, chpY, cmpB, cmpD and NdhD4), indicative of increased carbon metabolism. These differences in the strains’ response to elevated pCO₂ will lead to changes in the species population structure and distribution in the water column. This study shows that it is important to examine the effects of both pCO₂ and temperature, and to consider strain variation, to understand how species composition of natural systems may change under future climate conditions.

全球大气中CO ₂和温度的增加将影响水生系统，并影响淡水生境。一些研究表明，这些条件将促进蓝细菌的优势。需要更清楚地了解藻类和种内的菌株将如何响应较高的温度和CO ₂，特别是组合情况。这项研究检查了两种叶绿素（单生植物和Staurastrum）和两株蓝藻Raphidiopsis raciborskii菌株（直S07和盘绕的C03），以确定较高温度和CO ₂的组合水平会影响它们的生长和最大细胞浓度。连续培养用于比较28°C和30°C的稳态细胞浓度以及所有培养的CO ₂分压（pCO ₂），400和750 ppm，以及R在28°C时的1000 ppm 。 raciborskii菌株。这项研究表明，对于所有物种，水温对细胞浓度的影响均高于较高的pCO ₂。在绿藻类之间的响应存在明显差异，其中单栖蜘蛛优选28°C，而Staurastrum优选30°C。R. raciborskii菌株对温度升高和pCO的响应也存在差异_{如图2所示}，其中S07具有更大的细胞浓度增加。R. raciborskii的基因组分析表明，纯合菌株具有五个其他碳捕获基因（β-CA，chpY，cmpB，cmpD和NdhD4），表明碳代谢增加。菌株对升高的pCO ₂的反应中的这些差异将导致物种种群结构和水柱中分布的变化。这项研究表明，重要的是要检查两种pCO ₂的作用。 和温度，并考虑应变变化，以了解未来气候条件下自然系统的物种组成可能如何变化。