Abstract
The escalating occurrence of toxic cyanobacterial blooms worldwide is a matter of concern. Global warming and eutrophication play a major role in the regularity of cyanobacterial blooms, which has noticeably shifted towards the predomination of toxic populations. Therefore, understanding the effects of cyanobacterial toxins in aquatic ecosystems and their advantages to the producers are of growing interest. In this paper, the current literature is critically reviewed to provide further insights into the ecological contribution of cyanotoxins in the variation of the lake community diversity and structure through interspecies interplay. The most commonly detected and studied cyanobacterial toxins, namely the microcystins, anatoxins, saxitoxins, cylindrospermopsins and β-N-methylamino-L-alanine, and their ecotoxicity on various trophic levels are discussed. This work addresses the environmental characterization of pure toxins, toxin-containing crude extracts and filtrates of single and mixed cultures in interspecies interactions by inducing different physiological and metabolic responses. More data on these interactions under natural conditions and laboratory-based studies using direct co-cultivation approaches will provide more substantial information on the consequences of cyanotoxins in the natural ecosystem. This review is beneficial for understanding cyanotoxin-mediated interspecies interactions, developing bloom mitigation technologies and robustly assessing the hazards posed by toxin-producing cyanobacteria to humans and other organisms.
Highlights
In aquatic ecosystems, the primary producers, such as cyanobacteria, algae, bacteria and plants, often function as foundation as well as keystone species [1] because they drive primary production, play a pivotal role in food webs and nutrient cycling and create habitats for other species
LE-3, suggesting the protective role of MCs against the induced oxidative stress. These data demonstrated the diverse effects of cyanotoxins on the growth and physiology of phytoplankton species, which may explain the succession of the green algae following the collapse of toxic cyanobacterial blooms
Rasmussen et al [173] reported the minimal inhibitory concentration of 300 μg L−1 for CYN, extracted from R. raciborskii, against both gram-negative and gram-positive bacteria E. coli, B. subtilis, Staphylococcus aureus and Pseudomonas aeruginosa. These findings suggested that CYN was not a potent antibacterial agent at an environmentally relevant concentration
Summary
The primary producers, such as cyanobacteria, algae, bacteria and plants, often function as foundation as well as keystone species [1] because they drive primary production, play a pivotal role in food webs and nutrient cycling and create habitats for other species. Dolichospermum circinale (previously Anabaena circinalis), Aphanizomenon flos-aquae, Raphidiopsis raciborskii (previously Cylindrospermopsis raciborskii) and M. aeruginosa have been shown to impact other phytoplankton via their toxins [38,39]; e.g., by suppressing grazing, growth and reproduction of antagonists leading to mortality in some cases [40,41,42,43,44,45] It is unknown if all so-called “toxins” play a role as allelopathic biomolecules benefitting the producer. This review sets out to collect and assimilate the current knowledge regarding the allelopathic interactions of the major cyanotoxin groups and how they could serve as an advantage for cyanobacteria in aquatic communities by assessing the adverse effects reported on biota, which co-occur with cyanobacteria in aquatic environments
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