Antibiotic pollution promotes dominance by harmful cyanobacteria: A case study examining norfloxacin exposure in competition experiments

Abstract

Cyanobacterial harmful algal blooms (cyanoHABs) in freshwater lakes across the globe are often combined with other stressors. Pharmaceutical pollution, especially antibiotics in water bodies, poses a potential hazard in aquatic ecosystems. However, how antibiotics influence the risk of cyanoHABs remains unclear. Here, we investigated the effects of norfloxacin (NOR), one of the most widely used antibiotics globally, to a bloom‐forming cyanobacterium (Microcystis aeruginosa) and a common green alga (Scenedesmus quadricauda), under both mono‐ and coculture conditions. Taxon‐specific responses to NOR were evaluated in monoculture. In addition, the growth rate and change in ratio of cyanobacteria to green algae when cocultured with exposure to NOR were determined. In monocultures of Microcystis, exposure to low concentrations of NOR resulted in decreases in biomass, chlorophyll a and soluble protein content, while superoxide anion content and superoxide dismutase activity increased. However, NOR at high concentration only slightly affected Scenedesmus. During the co‐culture trials of Microcystis and Scenedesmus, the 5 μg · L−1 NOR treatment increased the ratio of Microcystis to co‐cultured Scenedesmus by 47.2%. Meanwhile, although Scenedesmus growth was enhanced by 4.2% under NOR treatment in monoculture, it was conversely inhibited by 63.4% and 38.2% when co‐cultured with Microcystis with and without NOR, respectively. Our results indicate that antibiotic pollution has a potential risk to enhance the perniciousness of cyanoHABs by disturbing interspecific interaction between cyanobacteria and green algae. These results reinforce the need for scientists and managers to consider the influence of xenobiotics in shaping the outcome of interactions among multiple species in aquatic ecosystems.

Antibiotic Pollution of Planktonic Ecosystems: A Review Focused on Community Analysis and the Causal Chain Linking Individual- and Community-Level Responses

“…), accelerating community succession toward a cyanobacterial bloom . In other words, antibiotics have the potential to enhance the destructive effects of harmful algal blooms by disrupting interspecific interactions between cyanobacteria and other algae . Additionally, inducible defenses constitute an important source of heterogeneity in natural phytoplankton communities; such defenses are altered by antibiotics.…”

Cyanobacterial Harmful Algal Blooms in Aquatic Ecosystems: A Comprehensive Outlook on Current and Emerging Mitigation and Control Approaches

“…Here, we highlight an emerging venue based on intra- and inter-species communication/competition/allopathic interactions that take place between toxic cyanobacteria, non-toxic cyanobacteria (mainly Microcystis sp. ), and other organisms, mainly (but not only) green algae, that may ultimately lead to the development of mitigation protocols (see [ 66 , 75 , 89 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 ] and references therein). An emerging example is the reduction of cyanoHAB populations that enables the persistence dominance of various non-toxic algae.…”

“…Similarly, when both organisms were treated with the antibiotic norfloxacin, the inhibition of S . quadricauda was much stronger when Microcystis was also present [ 135 ]. These and many other reports suggest that exposure of Microcystis to stress enhances the intensity of interspecies interactions.…”

The special and general mechanism of cyanobacterial harmful algal blooms

“…Some stressors in eutrophic waters include heavy metals, antibiotics, and dyes (Devarajan et al, 2015; Guo et al, 2020; Li et al, 2020). Despite the expected inhibitive effects of heavy metals on cyanobacterial growth (Richardson et al, 2018), some antibiotics are found to be promoting in two recent studies (Li et al, 2021; Xu et al, 2021). Here, three types of stress resistance are summarized in CyanoPATH: heavy metal and antibiotics, and mycosporine-like amino acids (MAAs) to shield ultraviolet light (Fig.…”