Cyanobacteria were present on the earth 3.5 billion years ago; since then they have colonized almost all terrestrial and aquatic ecosystems. They produce a high number of bioactive molecules, among which some are cyanotoxins. Cyanobacterial growth at high densities, forming blooms, is increasing in extension and frequency, following anthropogenic activities and climate changes, giving rise to some concern for human health and animal life exposed to cyanotoxins. Numerous cases of lethal poisonings have been associated with cyanotoxins ingestion in wild animal and livestock. In humans few episodes of lethal or severe human poisonings have been recorded after acute or short-term exposure, but the repeated/chronic exposure to low cyanotoxin levels remains a critical issue. The properties of the most frequently detected cyanotoxins (namely, microcystins, nodularins, cylindrospermopsin and neurotoxins) are here critically reviewed, describing for each toxin the available information on producing organisms, biosynthesis/genetic and occurrence, with a focus on the toxicological profile (including kinetics, acute systemic toxicity, mechanism and mode of action, local effects, repeated toxicity, genotoxicity, carcinogenicity, reproductive toxicity; human health effects and epidemiological studies; animal poisoning) with the derivation of health-based values and considerations on the risks for human health.

Cyanotoxins: producing organisms, occurrence, toxicity, mechanism of action and human health toxicological risk evaluation

Ecology of Cyanobacteria

Harmful algal blooms (HABs) are symptomatic of ecosystem imbalance, often caused by the many environmental changes that demonstrate the expanding global human footprint and climate change. HABs are a major issue in marine, brackish, and freshwater systems worldwide. HAB species include representatives from most major algal and cyanobacterial taxonomic groups, but, despite this diversity, many HAB taxa respond to similar broad environmental stimuli (e.g., nutrients, light) and employ similar growth and defense strategies to maximize growth and minimize losses. In inland waters, attention is focused on dense surface HABs caused by planktonic cyanobacteria (cHABs), and the past few decades have seen an apparent increase in cHAB frequency and geographic range. There has also been an apparent rise in blooms of eukaryotic phytoplankton, including invasive marine flagellates, while reports of thick shoreline and benthic mats of chlorophytes, cyanobacteria, and other benthic HABs are likewise increasing. Research has made tremendous advances in our understanding of HAB events, yet they remain poorly understood. This chapter provides an overview of these intriguing and challenging phenomena, which affect ecosystems and human societies. While HABs are as diverse as the water bodies they impact, we focus on some specific examples of known HAB taxa that affect inland waters in North America and highlight some of the important strategies used by these species to enable their excessive growth.

http://scitechconnect.elsevier.com/wp-content/uploads/2016/01/Wehr_Excerpt1.pdf

Harmful Algal Blooms

It is now clear that several of the filamentous bacteria in activated sludge wastewater treatment plants globally, are members of the phylum Chloroflexi. They appear to be more commonly found in treatment plants designed to remove nitrogen (N) and phosphorus (P), most of which operate at long sludge ages and expose the biomass to anaerobic conditions. The Chloroflexi seem to play an important beneficial role in providing the filamentous scaffolding around which flocs are formed, to feed on the debris from lysed bacterial cells, to ferment carbohydrates and to degrade other complex polymeric organic compounds to low molecular weight substrates to support their growth and that of other bacterial populations. A few commonly extend beyond the floc surface, while others can align in bundles, which may facilitate interfloc bridging and hence generate a bulking sludge. Although several recent papers have examined the phylogeny and in situ physiology of Chloroflexi in activated sludge plants in Denmark, this review takes a wider look at what we now know about these filaments, especially their global distribution in activated sludge plants, and what their functional roles there might be. It also attempts to outline why such information might provide us with clues as to how their population levels may be manipulated, and the main research questions that need addressing to achieve these outcomes.

The Phylogeny, Biodiversity, and Ecology of the Chloroflexi in Activated Sludge

An overview of the accumulation of microcystins in aquatic ecosystems

A review of current knowledge on toxic benthic freshwater cyanobacteria--ecology, toxin production and risk management.

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A review of current knowledge on toxic benthic freshwater cyanobacteria--ecology, toxin production and risk management.