Screening the toxicity and toxin content of blooms of the cyanobacterium Trichodesmium erythraeum (Ehrenberg) in northeast Brasil

Blooms of the cyanobacterium Trichodesmium occur in massive colored patches over large areas of tropical and subtropical oceans. Recently, the interest in such events has increased given their role in major nitrogen and carbon dioxide oceanic fluxes. Trichodesmium occurs all along the Brazilian coast and patches frequently migrate towards the coast. In this paper we screen the toxicity and toxin content of Trichodesmium blooms off the coast of Bahia state. Four samples, collected from February to April 2007, were analyzed. Organisms were identified and assessed for toxicity by means of several methods. Analogues of microcystins, cylindrospermopsins and saxitoxins were analyzed using HPLC. Microcystins were also assayed through ELISA. Results showed dominance of T. erythraeum, which makes up as much as 99% of cell counts. Other organisms found in smaller quantities include the dinoflagellates Prorocentrum minimum and P. rhathymum. Extracts from all samples delayed or interrupted sea urchin larval development, but presented no acute toxicity during a mouse bioassay. Saxitoxin congeners and microcystins were present at low concentrations in all samples, occurrences that had not previously been reported in the literature. Despite our finding of saxitoxin analogues and microcystins in Trichodesmium blooms, these toxins do not represent a potential harm to human health by primary contact. We conclude, based on our results and those reported in the recent literature, which differ from results published in 1963, that although toxins are present, there is no evidence that T. erythraeum blooms represent a threat to humans.

Screening the toxicity and toxin content of blooms of the cyanobacterium Trichodesmium erythraeum (Ehrenberg) in northeast Brasil

Blooms of the cyanobacterium Trichodesmium occur in massive colored patches over large areas of tropical and subtropical oceans. Recently, the interest in such events has increased given their role in major nitrogen and carbon dioxide oceanic fluxes. Trichodesmium occurs all along the Brazilian coast and patches frequently migrate towards the coast. In this paper we screen the toxicity and toxin content of Trichodesmium blooms off the coast of Bahia state. Four samples, collected from February to April 2007, were analyzed. Organisms were identified and assessed for toxicity by means of several methods. Analogues of microcystins, cylindrospermopsins and saxitoxins were analyzed using HPLC. Microcystins were also assayed through ELISA. Results showed dominance of T. erythraeum, which makes up as much as 99% of cell counts. Other organisms found in smaller quantities include the dinoflagellates Prorocentrum minimum and P. rhathymum. Extracts from all samples delayed or interrupted sea urchin larval development, but presented no acute toxicity during a mouse bioassay. Saxitoxin congeners and microcystins were present at low concentrations in all samples, occurrences that had not previously been reported in the literature. Despite our finding of saxitoxin analogues and microcystins in Trichodesmium blooms, these toxins do not represent a potential harm to human health by primary contact. We conclude, based on our results and those reported in the recent literature, which differ from results published in 1963, that although toxins are present, there is no evidence that T. erythraeum blooms represent a threat to humans.

Microphytoplankton structure from the neritic and oceanic regions of Pernambuco State - Brazil

This research was carried out to assess phytoplankton diversity, distribution and ecology on the Pernambuco Continental Shelf and Oceanic region (lat. 7º 33' 00" S to 8º 41' 50" S and long. 34º 04' 47" W to 35º 01' 20" W). Samples were collected during the Joint Oceanographics Projects (JOPS II-Leg 5) by double oblique hauls with a baby bongo net 64 µm mesh size at depth between 14 and 150 m in inshore and offshore waters respectively, in seven transects, totaling 34 stations. The temperature and salinity characterised the tropical water masses. The dissolved oxygen was oversaturated in all stations. The nutrient-low concentrations showed an oligothrophic pattern in the whole area. 173 specific and infraspecific taxa were identified: Dinophyta (103 taxa), Bacillariophyta (61 taxa), Cyanobacteria (7 taxa), Chlorophyta and Chrysophyta (1 taxon). The family Ceratiaceae presented the highest species number (47 taxa). The cyanobacteria Trichodesmium erythraeum Ehrenberg, Oscillatoria spp. and the diatom Leptocylindrus danicus Cleve had higher frequence of occurrence and abundance. Species diversity varied from 0.71 to 3.46 bits.cell-1 and this low index was due to Trichodesmium erythraeum bloom and evenness from 0.14 to 0.65, showing an unstable pattern. The oceanic planktonic species were responsible for the higher richness with 78 taxa, corresponding to 58.39% of the total microphytoplankton. The species association presented two groups. The first one divided in two subgroups: one associated to the neritic/oceanic and oceanic planktonic species and the other to the oligotrophic indicator species. The second group was composed of some key species which were the most abundant and frequent in the area. The first three Principal Component Analyses (PCAs) explained 50.91% of the data variance showing that the area is structured by two groups: one offshore composed by oligotrophic indicators, and another nearshore influenced by continental fluxes.

O presente trabalho foi desenvolvido com o objetivo de ampliar os conhecimentos sobre a diversidade, distribuição e ecologia da comunidade fitoplanctônica na Plataforma Continental de Pernambuco e área oceânica (lat. 7º 33' 00" S a 8º 41' 50" S e long. 34º 04' 47" O a 35º 01' 20" O). As coletas foram realizadas durante a prospecção Joint Oceanographics Project (JOPS II- Leg 5), através de arrastos oblíquos utilizando-se uma rede do tipo baby bongo com abertura de malha de 64 m a profundidades entre 14 m para as estações neríticas e 150 m para as estações oceânicas, em sete perfis perpendiculares à costa, totalizando 34 estações. A temperatura e a salinidade apresentaram características de Água Tropical. O oxigênio dissolvido manteve-se elevado durante todo em todas as estações. As baixas concentrações de nutrientes apresentaram um padrão oligotrófico em toda a área. Foram identificados 173 táxons específicos e infraespecíficos: Dinophyta (103 táxons); Bacillariophyta (61 táxons); Cyanobactéria (7 táxons); Chlorophyta e Chrysophyta (1 táxon). A família Ceratiaceae apresentou maior riqueza, com 47 táxons. As cianobactérias Trichodesmium erythraeum Ehrenberg, Oscillatoria spp. e a diatomácea Leptocylindrus danicus Cleve caracterizaram a área em termos de frequência de ocorrência e dominância, respectivamente. A diversidade específica variou de 0,71 a 3,46 bits.cél-1, sendo estes baixos índices caracterizados pelo predomínio de Trichodesmiumerythraeum. A equitabilidade variou de 0,14 a 0,65. As espécies marinhas planctônicas oceânicas se destacaram com 78 dos táxons representando 58,39% do microfitoplâncton total. A associação das espécies permitiu evidenciar dois grupos. O primeiro, subdivido em dois subgrupos: o primeiro associado às espécies planctônicas neríticas/oceânicas e oceânicas e o segundo, às espécies indicadoras de condições oligotróficas. O segundo grupo associou algumas espécies chave que caracterizaram a área em termos de dominância e frequência de ocorrência. Na análise dos componentes principais (ACP), os três primeiros fatores foram responsáveis por 50,91% da variância dos dados, mostrando que a área está estruturada por dois grupos: um composto por espécies indicadoras de oligotrofia e o outro, por espécies costeiras influenciadas por fluxo continental.