Toxic benthic freshwater cyanobacterial proliferations: Challenges and solutions for enhancing knowledge and improving monitoring and mitigation

Abstract

This review summarises knowledge on the ecology, toxin production, and impacts of toxic freshwater benthic cyanobacterial proliferations. It documents monitoring, management, and sampling strategies, and explores mitigation options. Toxic proliferations of freshwater benthic cyanobacteria (taxa that grow attached to substrates) occur in streams, rivers, lakes, and thermal and meltwater ponds, and have been reported in 19 countries. Anatoxin‐ and microcystin‐containing mats are most commonly reported (eight and 10 countries, respectively). Studies exploring factors that promote toxic benthic cyanobacterial proliferations are limited to a few species and habitats. There is a hierarchy of importance in environmental and biological factors that regulate proliferations with variables such as flow (rivers), fine sediment deposition, nutrients, associated microbes, and grazing identified as key drivers. Regulating factors differ among colonisation, expansion, and dispersal phases. New ‐omics‐based approaches are providing novel insights into the physiological attributes of benthic cyanobacteria and the role of associated microorganisms in facilitating their proliferation. Proliferations are commonly comprised of both toxic and non‐toxic strains, and the relative proportion of these is the key factor contributing to the overall toxin content of each mat. While these events are becoming more commonly reported globally, we currently lack standardised approaches to detect, monitor, and manage this emerging health issue. To solve these critical gaps, global collaborations are needed to facilitate the rapid transfer of knowledge and promote the development of standardised techniques that can be applied to diverse habitats and species, and ultimately lead to improved management.

First insights into the impacts of benthic cyanobacterial mats on fish herbivory functions on a nearshore coral reef

“…As stated by Duperron et al 38 , the 1700 described cyanobacterial species are only a subset of the actual diversity. Taxonomic studies of cyanobacteria have largely focused on freshwater pelagic cyanobacteria—which exhibit similar high diversity with many overlapping taxa to those identified here 12 —while tropical regions and marine benthic mats have been far less studied. New species and genera can be discovered in these habitats, which is of interest not only for the taxonomic but also chemical diversity 38 .…”

“…However, the chemical diversity that exists in other taxa that have not been taxonomically described yet remains largely unknown. Freshwater BCMs are better-studied thus provide some insights into the wide diversity and impacts of associated toxins 12 , and emphasise the need to expand research on marine BCMs. It’s likely that differences in the metabolites produced by different BCMs, along with variation in tolerance to the metabolites by different fish species, can in part explain discrepancies in observations of grazing on BCMs between this study and others (e.g.…”

“…Similarly to their better-studied freshwater counterparts 12 , proliferation of BCMs in coral reef ecosystems are associated with a wide range of problems due to their fast-growing opportunistic nature and their intrinsic toxic properties 1 . BCMs are notoriously competitive in interactions with corals, and often result in damage or mortality of coral tissue (e.g.…”

The Use of Biochar and Pyrolysed Materials to Improve Water Quality through Microcystin Sorption Separation

“…Recent studies indicate that cyanobacterial harmful algal blooms (cyanoHABs) are occurring more frequently in inland fresh waters (i.e., ponds, lakes, streams, and rivers) and estuaries worldwide [1][2][3][4]. Higher temperatures linked to global climate change and increased eutrophication have intensified cyanoHABs, posing significant environmental, social, and economic impacts partly due to the effects of toxins produced by several taxa [5][6][7][8].…”

“…Monitoring toxicity following such events in waterbodies can be complicated as cyanobacterial blooms contain complex mixtures of different classes of toxins [9][10][11]. Nevertheless, increased research efforts on the toxic impacts of these blooms under a changing climate and practical tools and methods for their management and remediation are clearly needed [4][5][6][7][8][9][10][11][12][13][14].…”