Micronutrients as growth limiting factors in cyanobacterial blooms; a survey of freshwaters in South East Australia

Facey Jordan A.; Rogers Terence A.; Apte Simon C.; Mitrovic Simon M.

摘要

The role of trace metal micronutrients in limiting cyanobacterial growth and structuring the phytoplankton community is becoming more evident. However, little is known regarding the extent of micronutrient limitation in freshwaters or which micronutrient conditions favour potentially-toxic cyanobacteria. To assess how freshwater phytoplankton respond to micronutrient and macronutrient additions, we conducted nutrient amendment bioassays at seven sites across South Eastern-Australia. Sites were variable in cyanobacterial cell densities and phytoplankton community compositions. At two sites, Mannus Lake and Burrendong Dam, micronutrient additions (iron, cobalt, copper, manganese, molybdenum and zinc) increased cyanobacterial growth, indicating micronutrient limitation. Both sites had cyanobacterial blooms present at the onset of the experiment, dominated by Chrysosporum ovalisporum at Mannus Lake and Microcystis aeruginosa at Burrendong Dam. This suggests that micronutrients may be an important regulator of the severity of cyanobacterial blooms and may become limiting when there is high competition for nutrient resources. The addition of the micronutrient mixture resulted in a higher proportion of cyanobacteria compared to the control and a lower diversity community compared to phosphorus additions, indicating that micronutrients can not only influence cyanobacterial biovolume but also their ability to dominate the phytoplankton community. This reinforces that micronutrient requirements of phytoplankton are often species specific. As micronutrient enrichment is often overlooked when assessing nutrient-constraints on cyanobacterial growth, this study provides valuable insight into the conditions that may influence cyanobacterial blooms and the potential contribution of micronutrients to eutrophication.

机译：痕量金属微量营养素在限制蓝藻生长和构建浮游植物群落中的作用变得越来越明显。然而，关于新鲜水域中的微量营养素限制或哪种微量营养素令有利于潜在的毒性蓝细菌的程度少。为了评估淡水浮游植物如何应对微量营养素和Macronutrient的添加，我们在澳大利亚南部的七个地点进行了营养修正生物测定。位点在蓝细菌细胞密度和浮游植物群落组合物中是可变的。在两个地点，甘露湖和伯伦松大坝，微量营养素添加（铁，钴，铜，锰，钼和锌）增加了蓝藻生长，表明微量营养素限制。两种位点在实验开始时存在樱桃般的绽放，其在曼努斯湖和Microcystis铜绿假单胞菌在伯伦松大坝的山孢菌卵巢粥。这表明微量营养素可能是蓝藻绽放严重程度的重要调节因子，并且当营养资源的竞争高时可能会受到限制。与对照和较低的多样性群落相比，与磷添加相比，添加微量营养素混合物的添加量较高，表明微量营养素不仅可以影响蓝藻生物植物，而且它们的主导植物群体的能力。这加强了浮游植物的微量营养素要求通常是特异性的物种。当评估营养限制时常被忽略微量营养素富集，该研究提供了对可能影响蓝藻绽放和微量营养素对富营养化的潜在贡献的条件提供有价值的洞察力。

Micronutrients as growth limiting factors in cyanobacterial blooms; a survey of freshwaters in South East Australia

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