Occurrence of toxin-producing cyanobacteria blooms in a Brazilian semiarid reservoir

Abstract

We report the occurrence of cyanobacterial blooms and the presence of cyanotoxins in water samples from the Armando Ribeiro Gonçalves reservoir (06° 08' S and 37° 07' W), located in the state of Rio Grande do Norte, in the semiarid region of northeastern Brazil. The cyanobacterial species were identified and quantified during the rainy and dry seasons in the year 2000. Cyanotoxins such as microcystins, saxitoxins and cylindrospermopsins were analyzed and quantified using hPLC and ELISA methods. The mixed toxic blooms of Cylindrospermopsis raciborskii, Microcystis spp (M. panniformis, M. protocystis, M. novacekii) and Aphanizomenon spp (Aphanizomenon gracile, A. cf. manguinii, A. cf. issastschenkoi) were persistent and represented 90-100% of the total phytoplankton species. Toxic cyanobacterial blooms from the Armando Ribeiro Gonçalves reservoir were analyzed and found to have three phases in relation to the annual cycle. During the rainy season, an intense toxic bloom of Cylindrospermopsis raciborskii was recorded along with saxitoxins (3.14 µg.L -1 ). During the transition period, between the rainy and dry seasons, different species of Microscytis occurred and microcystin as high as 8.8 µg.L -1 was recorded. In the dry season, co-dominance of Cylindrospermopsis raciborskii, Microcystis spp and Aphanizomenon spp occurred and the concentrations of saxitoxin remained very low. Our results indicate the presence of microcystins (8.8 µg.L -1 ) and saxitoxins (3.14 µg.L -1 ) into the crude water, with increasing concentrations from the second fortnight of April to late May 2000. The occurrence of toxic blooms in this reservoir points to a permanent risk of cyanotoxins in supply waters, indicating the need for the implementation of bloom control measures to improve the water quality. Exposure of the local population to cyanotoxins through their potential accumulation in fish muscle must also be considered.Keywords: reservoir, semiarid, cyanobacteria, microcystin, saxitoxin. RESUMO Ocorrência de florações tóxicas de cianobactérias em um reservatório no semi-árido brasileiroNós relatamos a ocorrência de florescimentos de cianobactérias e a presença de cianotoxinas em amostras de água do reservatório Armando Ribeiro Gonçalves (06° 08' S; 37° 07' W) situado no Estado do Rio Grande do Norte, na região semi-árida do Brasil. Cianobactérias foram identificadas e quantificadas nos períodos seco e chuvoso do ano 2000. Cianotoxinas tais como, microcistinas, saxitoxinas e cilindrospermopsinas foram quantificadas por hPLC e ELISA. Florescimentos tóxicos mistos de Cylindrospermopsis raciborskii, Microcystis spp (M. panniformis, M. protocystis, M. novacekii)

The introduced snail Melanoides Tuberculatus (Muller, 1774) (Mollusca: Thiaridae) in aquatic ecosystems of the Brazilian Semiarid Northeast (Piranhas-Assu River basin, State of Rio Grande do Norte)

“…The phytoplankton biomass is normally high (>100 mm 3 .L -1 ). In this reservoir as well, Costa et al (2006) reported sporadic blooms of toxic algae, mainly Microcystis spp. In the present study, samples were taken for analysis of the benthic community in two stages.…”

Análise da presença do fitoplâncton em bacia integrante do Projeto de Integração do Rio São Francisco, região semiárida, Nordeste brasileiro

“…Os organismos geralmente dominantes nesses ambientes e em alguns reservatórios podem chegar a compor entre 50 a 100% da densidade total, sendo considerada consequência da eutrofização (COSTA, 2003;COSTA et al, 2006;, PANOSSO et al, 2007.…”

“…Rodrigues (2004) relata que, historicamente, o fitoplâncton de ambientes lóticos tem recebido menos atenção em estudos limnológicos, pois a medição das variáveis ambientais é mais difícil em um hábitat que se modifica rapidamente tanto no tempo como no espaço. No entanto, em reservatórios de abastecimento público, espécies potencialmente tóxi-cas, como as cianobactérias, foram designadas como bioindicadoras da qualidade da água (COSTA et al, 2006;ARAGÃO et al, 2007;BROOKE et al, 2008). Dessa forma, conhecimentos sobre a composição, abundân-cia e distribuição de espécies da comunidade fitoplanctônica nos rios e reservatórios que compõem as bacias hidrográficas, sobretudo aquelas localizadas em região semiárida, são relevantes para a compreensão e o monitoramento da qualidade da água utilizada para seus diversos fins.…”

Degradation of cyanotoxins (microcystin) in drinking water using photoelectrooxidation

“…The occurrence of cyanobacterial blooms and the presence of cyanotoxins in water samples from the Armando Ribeiro Gonçalves reservoir, located in the state of Rio Grande do Norte, in the semiarid region of northeastern Brazil was reported (by Costa et al (2006). In the State of Rio Grande do Sul, southern Brazil, cyanobacterial blooms, particularly Microcystis aeruginosa, have been described in the Patos lagoon and its estuary at irregular time intervals in the last two decades (Yunes et al, 1996).…”