School of Geosciences, University of South Florida, Tampa, FL 33620, United States; Department of Ecology and Environmental Studies, Florida Gulf Coast University, Fort Myers, FL, United States.
Department of Ecology and Environmental Studies, Florida Gulf Coast University, Fort Myers, FL, United States.
Harmful Algae. 2024 Mar;133:102587. doi: 10.1016/j.hal.2024.102587. Epub 2024 Feb 5.
Hydrogen peroxide has gained popularity as an environmentally friendly treatment for cyanobacterial harmful algal blooms (cHABs) that takes advantage of oxidative stress sensitivity in cyanobacteria at controlled concentrations. Higher concentrations of hydrogen peroxide treatments may seem appealing for more severe cHABs but there is currently little understanding of the environmental impacts of this approach. Of specific concern is the associated microbial community, which may play key roles in the succession/recovery process post-treatment. To better understand impacts of a high concentration treatment on non-target microbial communities, we applied a hydrogen peroxide spray equating to a total volume concentration of 14 mM (473 mg/L, 0.04%) to 250 L mesocosms containing Microcystis bloom biomass, monitoring treatment and control mesocosms for 4 days. Cyanobacteria dominated control mesocosms throughout the experiment while treatment mesocosms experienced a 99% reduction, as determined by bacterial amplicon sequencing, and a 92% reduction in bacterial cell density within 1 day post-treatment. Only the bacterial community exhibited signs of regrowth, with a fold change of 9.2 bacterial cell density from day 1 to day 2. Recovery consisted of succession by Planctomycetota (47%) and Gammaproteobacteria (17%), which were likely resilient due to passive cell component compartmentalization and rapid upregulation of dnaK and groEL oxidative stress genes, respectively. The altered microbiome retained beneficial functionality of microcystin degradation through a currently recognized but unidentified pathway in Gammaproteobacteria, resulting in a 70% reduction coinciding with bacterial regrowth. There was also an 81% reduction of both total nitrogen and phosphorus, as compared to 91 and 93% in the control, respectively, due to high expressions of genes related to nitrogen (argH, carB, glts, glnA) and phosphorus (pntAB, phoB, pstSCB) cycling. Overall, we found a portion of the bacterial community was resilient to the high-concentration hydrogen peroxide treatment, resulting in Planctomycetota and Gammaproteobacteria dominance. This high-concentration treatment may be suitable to rapidly end cHABs which have already negatively impacted the aquatic environment rather than allow them to persist.
过氧化氢作为一种环保型处理方法，已在应对蓝藻有害藻华（cHAB）方面得到了广泛应用，该方法利用了蓝藻在受控浓度下对氧化应激的敏感性。较高浓度的过氧化氢处理对于更严重的 cHAB 似乎更具吸引力，但目前对这种方法的环境影响知之甚少。特别值得关注的是相关的微生物群落，它可能在处理后演替/恢复过程中发挥关键作用。为了更好地了解高浓度处理对非靶标微生物群落的影响，我们应用了一种过氧化氢喷雾，相当于 250 L 中尺度培养箱中总容积浓度为 14 mM（473 mg/L，0.04%）的浓度，对含有微囊藻水华生物量的中尺度培养箱进行处理，监测处理和对照中尺度培养箱 4 天。在整个实验过程中，蓝藻在对照中尺度培养箱中占主导地位，而在处理中尺度培养箱中，细菌扩增子测序结果表明，蓝藻减少了 99%，细菌细胞密度在处理后 1 天内减少了 92%。只有细菌群落表现出再生迹象，从第 1 天到第 2 天，细菌细胞密度增加了 9.2 倍。恢复由 Planctomycetota（47%）和 Gammaproteobacteria（17%）组成，这可能是由于被动的细胞成分区室化和 dnaK 和 groEL 氧化应激基因的快速上调，使它们具有弹性。改变的微生物组通过在 Gammaproteobacteria 中目前公认但尚未确定的途径保留了微囊藻降解的有益功能，导致与细菌再生同时发生的 70%的减少。与对照相比，总氮和总磷的减少量分别为 81%和 91%，分别为 93%，这是由于与氮（argH、carB、glts、glnA）和磷（pntAB、phoB、pstSCB）循环相关的基因的高表达所致。总的来说，我们发现一部分细菌群落对高浓度过氧化氢处理具有弹性，导致 Planctomycetota 和 Gammaproteobacteria 占主导地位。这种高浓度处理可能适用于迅速结束已经对水生环境产生负面影响的 cHAB，而不是让它们持续存在。
