Use of Myriophyllum aquaticum to inhibit Microcystis aeruginosa growth and remove microcystin-LR

Abstract

Harmful algal blooms are one of the greatest challenges when preserving water sources, especially when involving cyanobacteria such as Microcystis aeruginosa. Finding remediation possibilities is needed, and one of them has been the use of macrophytes such as the species Myriophyllum, which have presented allelopathic mechanisms of phytoplankton control. Thus, this work aimed to evaluate the inhibition of M. aeruginosa cell growth in a co-exposure with Myriophyllum aquaticum and the influence on microcystin-LR concentration. The experiments were carried out using a culture of M. aeruginosa (1x106 cells mL-1) in a co-exposure with M. aquaticum for seven days. The inhibitory effects were investigated by counting the cells; the effects on photosynthetic pigments were measured and microcystin-LR was quantified in the culture medium on the last experimental day. To evaluate the possible effects of competition for nutrients and space, the concentration of total orthophosphate was quantified and treatment with plastic plants was used. The experiments with Myriophyllum aquaticum achieved the total inhibition of M. aeruginosa growth and a significant reduction of the photosynthetic pigments (> 98%). Additionally, we observed a reduction of microcystin-LR concentration (79%) in the tests with macrophytes when compared to the control. Competition for space and nutrients was not observed, demonstrating that the effects on M. aeruginosa were caused by aquatic macrophyte presence. These results may indicate that M. aquaticum causes inhibitory effects on cyanobacteria growth by allelopathic effects and removes microcystin-LR.

Enhancing Biocontrol of Harmful Algae Blooms: Seasonal Variation in Allelopathic Capacity of Myriophyllum aquaticum

“…The use of allelopathic applications from submerged aquatic macrophytes can be considered a promising strategy for controlling cyanobacteria. This technique is inspired by natural phenomena and offers a nature-based solution [15,18,24]. In this context, the use of the Myriophyllum genus is reported to show a higher presence of phenolic compounds in their phytochemical composition [22][23][24]26,36,37].…”

“…This technique is inspired by natural phenomena and offers a nature-based solution [15,18,24]. In this context, the use of the Myriophyllum genus is reported to show a higher presence of phenolic compounds in their phytochemical composition [22][23][24]26,36,37]. It has already been identified that phenolic compounds can be produced by macrophytes of this genus and may act as allelochemicals.…”

“…In in vivo experiments, the allelopathic potential of M. aquaticum on cyanobacteria has already been proven, evidencing its allelopathic capacity and its relationship with phenolic compounds. [22][23][24]36]. However, the phytochemical composition of macrophytes may vary depending on spatial and temporal factors, which can affect their allelopathic capacity to inhibit cyanobacteria [26,27,37] demanding a better comprehension of this dynamic.…”

“…The pigment chlorophyll-a and accessory pigments such as phycoerythrin, phycocyanin, and allophycocyanin are essential for the reactions in photosynthesis [42]. When interferences occur on these pigments, they can generate inefficiencies and reductions in the photosynthetic potential of cyanobacteria, which highlights the importance of analyzing these pigments [24,42]. In this context, it has been proven that allelochemicals can cause effects on the photosynthetic apparatus.…”

“…In this context, submerged aquatic macrophytes contribute to the maintenance of water bodies, mainly through local oxygenation, and the control of phytoplankton by releasing allelochemicals into the aquatic environment to reduce competition for light, carbon, and nutrients [9,15,17,18]. Among the species of submerged aquatic macrophytes, the genus Myriophyllum has been studied due to its allelopathic capacity in cyanobacteria, mainly through the production of allelochemicals [20][21][22][23][24]. The major class with an inhibitory potential on cyanobacteria is phenolic compounds [9,25,26].…”