The role of nitrogen and phosphorus in promoting cyanobacterial blooms has been researched for many decades. In contrast, much less is known about the effect of trace metals on regulating cyanobacterial bloom formation. This is particularity relevant for nitrogen-fixing species, as some trace metals act as co-factors in nitrogenase and nitrite reductase enzymes. In the present study, we assessed the response of two nitrogen-fixing species, Dolichospermum lemmermannii and Dolichospermum planctonicum, to copper (Cu), cobalt (Co), molybdenum (Mo), iron (Fe) and nitrogen (N) using a culture-based approach. Response surface modelling showed growth rates in D. planctonicum were positively influenced by increased Co and Fe (p < 0.05), whereas Fe (p < 0.001) and Mo (p < 0.05) increased growth rates in D. lemmermannii. Heterocyst frequency in D. planctonicum was associated with nitrogen (negative response, p < 0.001) and all trace metals tested (positive; p < 0.001 or < 0.05) except Mo. Nitrogen had a strong negative effect (p < 0.001), and Fe a positive (p < 0.01) impact on heterocyst frequency in D. lemmermannii. These results indicate that in addition to regulating nitrogen and phosphorus inputs, management efforts should consider minimising trace metals from entering waterbodies.

氮和磷在促进蓝藻花开中的作用已有数十年的研究。相反，关于痕量金属对调节蓝藻水华形成的影响知之甚少。这对于固氮物种特别重要，因为一些微量金属在固氮酶和亚硝酸还原酶中起辅助因子的作用。在本研究中，我们使用培养物评估了两个固氮物种，Dolichospermum lemmermannii和Dolichospermum planctonicum，对铜（Cu），钴（Co），钼（Mo），铁（Fe）和氮（N）的响应基于方法。响应面建模表明，D. Planctonicum的生长速率受Co和Fe（p <0.05），而铁（D. lemmermannii  ）中的Fe（p <0.001）和Mo（p  <0.05）增加了生长速率。扁平苔藓中的胚泡频率与氮（负响应，p  <0.001）和所有测试的微量金属（正；p  <0.001或<0.05）相关，除了钼。氮具有很强的负面影响（p  <0.001）和铁对D. lemmermannii的囊肿 频率有积极的影响（p <0.01）。这些结果表明，除了调节氮和磷的输入外，管理工作还应考虑将进入水体中的痕量金属减至最少。