Impact of temperature and species interaction on filamentous cyanobacteria may be more important than salinity and increased pCO2 levels

A future business-as-usual scenario (A1FI) was tested on two bloom-forming cyanobacteria of the Baltic Proper, Nodularia spumigena and Aphanizomenon sp., growing separately and together. The projected scenario was tested in two laboratory experiments where (a) interactive effects of increased temperature and decreased salinity and (b) interactive effects of increased temperature and elevated levels of pCO2 were tested. Increased temperature, from 12 to 16 °C, had a positive effect on the biovolume and photosynthetic activity (F v/F m) of both species. Compared when growing separately, the biovolume of each species was lower when grown together. Decreased salinity, from 7 to 4, and elevated levels of pCO2, from 380 to 960 ppm, had no effect on the biovolume, but on F v/F m of N. spumigena with higher F v/F m in salinity 7. Our results suggest that the projected A1FI scenario might be beneficial for the two species dominating the extensive summer blooms in the Baltic Proper. However, our results further stress the importance of studying interactions between species.

本研究针对波罗的海本部的两种水华蓝藻——泡沫节球藻（Nodularia spumigena）与束丝藻属（未定种）（Aphanizomenon sp.），设置单独培养与共培养两种模式，对未来常规发展情景（A1FI）展开验证。该预估情景通过两组室内实验进行验证：其一为升温与盐度降低的交互效应实验，其二为升温与二氧化碳分压（pCO2）升高的交互效应实验。实验结果显示，温度从12℃升至16℃对两种藻的生物体积与光合活性（F v/F m）均具有正向影响；与单独培养时相比，两物种共培养时的生物体积均更低。盐度从7降至4，以及二氧化碳分压（pCO2）从380 ppm升至960 ppm，对两种藻的生物体积均无显著影响，但会影响泡沫节球藻的F v/F m值：在盐度为7时，其F v/F m值更高。本研究结果表明，预估的A1FI情景或对波罗的海本部夏季大规模水华的两大优势物种有利，但同时强调，探究物种间的相互作用至关重要。