The effect of saxitoxins (STX) on phytoplankton species is poorly understood. To date, no correlation between STX concentrations and phytoplankton physiology has been reported. We investigated the effect of STX (STX+, 0.5-10 μg L −1 total STX) and non-STX (STX−, 0.5-10 μg L −1 total STX biomass equivalent) extracts of Cylindrospermopsis raciborskii on Microcystis wesenbergii BCCUSP11, Microcystis aeruginosa BCCUSP232 (microcystin producing), Scenedesmus acuminatus UFSCar036, and Monoraphidium convolutum CMEA/UFF0201 under controlled laboratory conditions. Both STX+ and STX− extracts inhibited the cell density and specific growth rate of M. wesenbergii, M. aeruginosa, and S. acuminatus. However, the effect of STX+ extract on the phytoplankton strains was significantly higher than that of STX− extract. M. convolutum, on the other hand, was tolerant as both STX+ and STX− extracts did not significantly reduce its cell density and specific growth rate (day −1). The exposure of M. aeruginosa to STX+ and STX− resulted in higher total (intracellular and extracellular) microcystin concentration than the control. STX concentrations had a significant negative correlation with cell density and growth response of the phytoplankton strains investigated in this study. Conclusions can be made that although both STX+ and STX− extracts of C. raciborskii inhibited the growth of some phytoplankton species, the STX+ extracts were more toxic. Keywords Growth inhibition. Cyanotoxins. Phytoplankton. dc-Saxitoxin. Neo-saxitoxin. Microcystins on sodium channels in both prokaryotes and eukaryotes (Neilan et al. 2013). STX are of high ecotoxicological risk due to the toxicity they induce in fish, mussels, copepods, mammals, and birds (Landsberg 2002). A number of cyanobacteria such as Aphanizomenon flos-aquae, Cylindrospermopsis raciborskii, Lyngbya spp., and Anabaena spp. synthesize STX in freshwater ecosystems. However, the production of this group of toxins tends to be strain specific (Molica et al. 2002; Bernard et al. 2003; Wiegand and Pflugmacher 2005; Al-Tebrineh et al. 2010). The discovery that C. raciborskii produces STX and cylindrospermopsin has made it an important cyanobacterium to be monitored in aquatic ecosystems. This is due to the increased frequency of its occurrence, scientific interest, improved water quality monitoring, availability of suitable habitat, and in some cases, its invasion of new habitats (Figueredo et al. 2007; Kling 2009; Sukenik et al. 2012). The cosmopolitan and increasing distribution of C. raciborskii is easily traced to its ecophysiological adaptation and tolerance to changing physicochemical

Our objective was to investigate crude extracts toxic (MC+) and non-toxic (MC-) effects on the growth of Microcystis panniformis, Microcystis aeruginosa and Microcystis wesenbergii. Cultures were submitted to extracts MC+ at 5 and 10 MC µg.L-1 , and to MC-equivalent weight of these concentrations. Both crude extracts worked toward reducing the growth of M. wesenbergii and stimulating the growth of M. panniformis. Likewise, M. aeruginosa was inhibited by addition of crude MC-extract. The action of microcystins at concentrations commonly found in natural environments, plus the presence of other substances in intracellular M. aeruginosa produced differentiated effects in Microcystis spp.

O estado do Espírito Santo (Brasil) tem sido pouco explorado em termos de microalgas e cianobactérias de ambientes aquáticos continentais, apesar de possuir doze bacias hidrográficas, tendo a maior contribuição, em termos de volume de água da bacia do rio Doce. Este fato é resultado do baixo número de pesquisadores e instituições com pesquisas ecológicas e taxômicas. As primeiras investigações limnológicas com microalgas e cianobactérias ocorreram na década de 90, tendo avanço considerável em lagoas costeiras, lagos, rios e represas a partir da década de 2000, tanto com fitoplanctôn quanto com o perifíton, devido ao incremento de pesquisadores e editais de pesquisa. Este estudo cienciométrico visou identificar tendências das pesquisas já realizadas, apontando os ecossistemas aquáticos mais estudados e os autores dos artigos. Os resultados evidenciaram que a maioria dos estudos se concentrou na ecologia das comunidades, com listas de táxons; raros foram os estudos taxonômicos; poucos foram os trabalhos experimentais para compreensão de fatores reguladores das comunidades. Inúmeras lacunas precisam ser preenchidas, especialmente no que tange ao: levantamento da biodiversidade nas diferentes regiões do estado, com ênfase em taxonomia; desenvolvimento de pesquisas experimentais para compreensão de fatores reguladores das comunidades; estudos preditivos frente a impactos ambientais; uso destas comunidades como bioindicadores de impactos ambientais; estudos biotecnológicos com microalgas; pesquisas que abordem impactos na saúde pública relacionados, principalmente, com as florações de cianobactérias potencialmente tóxicas; realização de testes de hipóteses ecológicas. Há também a necessidade e relevância de publicações em revistas internacionais de maior impacto e com colaboradores nacionais e internacionais e o estabelecimento de parcerias com instituições externas ao Espírito Santo e ao Brasil. Os novos direcionamentos favorecerão o incremento do conhecimento das comunidades fitoplanctônica e perifítica nos ecossistemas aquáticos continentais do Espírito Santo e fornecerão subsídios para a tomada de medidas de recuperação e/ou preservação. CONTINENTAL MICROALGAE AND CYANOBACTERIA IN ESPÍRITO SANTO STATE: PAST, PRESENT AND FUTURE: The Espírito Santo State (Brazil) has been little explored in terms of microalgae and cyanobacteria from inland waters, despite its twelve hydrographic basins and being the greatest contribution in water volume of the Doce river basin. This fact is the result of the low number of researchers and institutions with research lines about freshwater ecology and microalgae taxonomy. Literature records indicate that the early limnological researches that studied microalgae were published in the 1990s, with a considerable increase in studies in coastal lagoons, lakes, rivers, and dams from the 2000s onwards, about phytoplankton and periphyton, due to the increase in the number of researchers and more research notices. The present scientometric work aimed to identify trends in the past studies, showing the aquatic ecosystems with the greatest number of studies and the authors of the articles. Our results showed that most studies focused on aquatic ecology and the community with lists of taxa; taxonomic studies were rares; there is little experimental work to understand community regulatory factors. Numerous gaps need to be filled, especially regarding to biodiversity in different regions of the state, with accurate taxonomy studies; more experimental research to understand regulatory factors in communities and predictive studies on environmental impacts; biotechnological studies; research related to public wealth and cyanobacteria blooms; and studies testing ecological hypotheses. It is also necessary to consider the needs and relevance of publications in international journals with greater impact and with national and international collaborators, establishing partnerships with institutions outside Espírito Santo and Brazil. The new directions will favor the increase of knowledge of the phytoplankton and periphytic communities in the continental aquatic ecosystems of Espírito Santo and will provide subsidies for taking measures for their recovery and/or preservation.