Human poisoning by microcystin has been recorded in many countries, including Brazil, where fatal cases have already occurred. The Amazon River is the main source of drinking water in municipalities such as Macapá, where there is no monitoring of cyanobacteria and cyanotoxins. This study investigated the presence of cyanobacteria and cyanotoxins in samples from a drinking water treatment plant (DWTP) that catches water from the Amazon River. The toxin analyses employed ELISA, LC/MS, and molecular screening for genes involved in the production of cyanotoxins. The sampling was carried out monthly from April 2015 to April 2016 at the intake (raw water) and exit (treated water) of the DWTP. This study reports the first detection of microcystin-LR (MC-LR) in the Amazon River, the world’s largest river, and in its treated water destined for drinking water purposes in Macapá, Brazil. The cyanobacterial density and MC-LR concentration were both low during the year. However, Limnothrix planctonica showed a density peak (± 900 cells mL⁻¹) in the quarter of June–August 2015, when MC-LR was registered (2.1 µg L⁻¹). Statistical analyses indicate that L. planctonica may produce the microcystin.

During the various hydrological periods in 2011, we studied the phytoplankton along an 87-km stretch of the Araguari and Falsino rivers, which are located in the eastern Brazilian Amazon, in the state of Amapá, Brazil, the most ecologically preserved state in the country. In the study area, the aquatic ecosystem is under pressure from human activities such as, mining, hydroelectric power generation and urbanization, which contrast with the surrounding areas that are designated for biodiversity conservation. The aim of this study was to characterize the composition, frequency and richness of algae species and also to identify spatial-temporal patterns of taxa distribution. During the study period, we identified 185 taxa (136 species in 49 genera). The division Chlorophyta (class: Zygnematophyceae) presented the greatest number of taxa, whereas the division Rhodophyta accounted for only 1% of the taxa recorded. Most of the species identified (69%) were classified as sporadic in occurrence. The few taxa that were classified as common belonged mainly to the group Bacillariophyta. Species richness was greatest richness in the lentic stretches (in a reservoir) and in November (during the dry season). Of the 185 taxa identified, 174 are new records for the state of Amapá

The Amazon region contains a great diversity of species, and the Amazon River basin accounts for almost 20% of all the freshwater in the world. Despite the favorable environmental conditions in this region, little is known about the cyanobacterial diversity of this waterbody, especially at the mouth of the river. In this paper, we used the polyphasic approach to identify 14 cyanobacterial strains isolated in the Amazon River on the inlet site from a drinking water supply located close to the river mouth. The isolated strains were characterized based on morphology, behavior in culture, 16S rRNA gene sequencing, phylogenetic analysis and potential for toxin production. The isolated strains belong to seven different genera, namely, Alkalinema, Cephalothrix, Limnothrix, Leptolyngbya, Phormidium, Pseudanabaena and an unidentified Nostocales taxa that may represent a new genus. Strikingly, there were no new species, nor detection of gene clusters associated with cyanotoxin production. However, the phylogenetic placements of the Amazonian strains of Limnothrix and Pseudanabaena provide new insight into the taxonomy of these genera, reinforcing the need for taxonomic revision.

The records of blooms and cyanotoxins in the Brazilian Legal Amazon are scarce and do not represent the reality observed in recent years when there was an increase in notifications and studies carried out in this region. In this article, we carefully analyzed 48 studies to identify the locations where the blooms occurred, the most frequent species, and the tests performed to detect cyanotoxins within the territory of the Brazilian Legal Amazon. The analyzed studies identified approximately 145 taxa of cyanobacteria, and the most frequent species belong to the genera Microcystis and Planktothrix. The most frequently detected cyanotoxin was microcystin, and, in some locations, even with a low cell density, there was the production of toxins. In most cases, Microcystis and Dolichospermum were the major genera associated with blooms and toxin production. The state of Pará had the highest number of records of toxin-producing cyanobacteria, including records of seasonal events, while Acre had no records. This work contributes to our knowledge of the geographic distribution and occurrence of cyanobacteria and cyanotoxins in the Brazilian Amazon and proposes new strategies for improving the monitoring of cyanotoxins in the Amazon region.

O fitoplâncton é formado por microalgas e cianobactérias, fornecedores de oxigênio para o meio aquático. Em ecossistemas desequilibrados esses organismos podem se multiplicar e produzir toxinas que afetam a saúde humana e animal. Este estudo teve como objetivo identificar padrões de densidade no fitoplâncton da água bruta da ETAm e relacionar a influência de fatores físicos, químicos e ambientais sobre a densidade das espécies. As amostragens foram realizadas entre maio de 2019 e agosto de 2020 (exceto em março-maio/2020, devido ao isolamento social). Foram identificados 86 táxons: Bacillariophyta (45), Cyanophyta (18), Chlorophyta (10), Charophyta (10), Dinophyta (1), Euglenophyta (1) e Rhodophyta (1), sendo as cianobactérias e diatomáceas os grupos mais abundantes. E as espécies mais abundantes foram Aulacoseira granulata e Limnothrix planctonica, respectivamente. Em relação à densidade de cianobactérias, observou-se que há padrão de aumento no período maio-agosto similar aos anos anteriores (2015-2016). Porém a densidade de cianobactérias observada neste estudo em 2019 (7083,2 cels. mL-1) foi 7x maior que em anos anteriores (1090 cels.mL-1 em 2015), todavia ainda estão em conformidade com os padrões estabelecidos pelo Ministério da Saúde (<10.000 cels.mL-1). Em junho e julho de 2020, quando era esperado o pico de cianobactérias, ocorreu queda expressiva na densidade. Pode-se inferir que isto ocorreu pela relação entre o aumento do isolamento social em Macapá e a diminuição da abundância de cianobactérias observada neste período de 2020 (R2= 0,94). Quanto à influência dos parâmetros ambientais, a transparência da água foi o parâmetro com maior influência na densidade de cianobactérias.