Acute toxicity of Microcystis spp. (Cyanobacteria) bloom on Moina minuta (Cladocera) in a tropical reservoir, Northeastern Brazil

Abstract

Worldwide cyanobacterial blooms have been registered, where harmful species dominance is associated to producing of toxic compounds (cyanotoxins) with adverse effects on several organisms. Acute toxicity of crude extracts from Microcystis bloom occurring in Mundaú reservoir was evaluated by bioassays with the neotropical Cladocera Moina minuta. Samples were taken in the reservoir during the rainy (April/2012) and dry season (September/2012). Cyanobacterial analyses were performed by identification on optical microscopy and direct counting using an inverted microscope. Bloom samples were frozen, lyophilized and re-suspended in deionized water for preparation of extracts. Tests with the cladoceran were carried out in test tubes with different concentrations of the crude extract, diluted in 10 mL reconstituted water. In both rainy and dry periods, densities of Microcystis spp. were above 15x10 3 ind mL-1. Microcystin concentrations in the extracts were 0.70 (+ 0,009) (rainy season) and 0.69 (+ 0,005) (dry season) μg g-1. The LC 50 (48h) of crude extract for both rainy and dry periods was 160 (100-255) and 72 (4-1113) mg L-1 , respectively. These results indicated that extracts of Microcystis spp. were acutely toxic to M. minuta population with suggesting that such events represent potential toxicity to zooplankton.

Qualidade da água superficial de reservatórios temporários localizados entre a região semiárida e o litoral do Nordeste Brasileiro

“…Além destes íons, outras substâncias que ocorrem naturalmente nos reservatórios, podem infligir efeitos deletérios ao ecossistema aquático. As toxinas produzidas por cianobactérias, conhecidas por cianotoxinas, são comuns em vários reservatórios do nordeste do Brasil (Vilar et al, 2014;Borges et al, 2015) são um exemplo disso. Ao avaliar o efeito tóxico de florações de Microcystis sp sobre a mobilidade de M. minuta, Vilar et al (2014) mostraram que, embora durante o período chuvoso e seco, a composição da floração seja semelhante, a toxicidade foi maior no período seco (Setembro/2012).…”

“…As toxinas produzidas por cianobactérias, conhecidas por cianotoxinas, são comuns em vários reservatórios do nordeste do Brasil (Vilar et al, 2014;Borges et al, 2015) são um exemplo disso. Ao avaliar o efeito tóxico de florações de Microcystis sp sobre a mobilidade de M. minuta, Vilar et al (2014) mostraram que, embora durante o período chuvoso e seco, a composição da floração seja semelhante, a toxicidade foi maior no período seco (Setembro/2012). Outro trabalho que mostra o potencial tóxico destas substâncias aos cladóceras, detectou efeito tóxico agudo à M. micrura, quando exposta a águas de um reservatório tropical no Rio de Janeiro, Brasil (Ferrão-Filho et al, 2009).…”

Experimental Studies on Zooplankton-Toxic Cyanobacteria Interactions: A Review

“…The adverse effects of cyanobacterial extracts have been studied since the early 2000s [ 30 , 92 ] on several cladocerans including Moina macrocopa , Ceriodaphnia dubia , Ceriodaphnia silvestrii, and Daphnia similis . Ever since, many studies indicate the toxicity of extracts from blooms on rotifers and cladocerans [ 29 , 38 , 39 , 41 , 43 , 93 ]. These studies are based on acute and chronic toxicity tests and data related to survivorship and fecundity of the test zooplankton.…”

An Overview of Cyanobacteria Harmful Algal Bloom (CyanoHAB) Issues in Freshwater Ecosystems

“…Therefore, they cause changes in the trophic levels and adverse impacts on the functioning of freshwater ecosystems. This begins with the zooplankton community, which has its composition changed, especially by the mortality of certain species resulting therefore in the reduction of their diversity [59,109,116,117]. For example, the copepod Diaptomus birgei was the most sensitive to microcystins with a lethal concentration (LC 50 ) at 48 h of 0.45 to 1.0 μg mL −1 followed by the cladoceran Daphnia pulex, D. hyaline, and D. pulicaria with LC 50 at 48 h of 9.6, 11.6, and 21.4 μg L −1 , respectively [109].…”