Abstract This study addressed the occurrence and distribution of benthic microalgae, with emphasis on toxic species, on different substrates (macroalgae, seagrass and sediments) along the outer, euhaline zone of the Estuarine Complex of Paranaguá Bay, southern Brazil, from July 2015 to May 2016. Canonical analysis of principal coordinates (CAP) was used to identify the potential environmental drivers of microphytobenthic assemblage structure. A total of 18 potentially toxic benthic microalgae species were reported, including 7 dinoflagellates, 9 cyanobacteria, one diatom and one euglenophyte. The abundance of all potentially toxic microalgae varied consistently along the investigated period. Dinoflagellates dominated the microalgae assemblage in July and September 2015. Mean densities on macrophytes ranged from 33.6 cells g-1 in May 2016 to 775.6 cells g-1 in September 2015, being positively correlated with dissolved nitrogen-nutrients, water transparency, salinity, and chlorophyll-a. Prorocentrum cf. lima was the most frequent and abundant dinoflagellate. Overall, the highest abundance of toxic species occurred in February 2016, when cyanobacterial mats dominated by Lyngbya cf. aestuarii were observed throughout the estuary associated with periods of heavier rainfall and higher turbidity (shallower Secchi depth). At that time, a selected microphytobenthic extract exhibited acute toxicity on nauplii of the brine shrimp Artemia salina in the laboratory.

Este estudo investigou a distribuição espacial e temporal de espécies toxigênicas de fitoplâncton entre outubro de 2010 e abril de 2012 na Baía de Guaratuba, Estado do Paraná, Brasil, onde as atividades de maricultura têm se intensificado nos últimos anos. As maiores abundâncias de Pseudo-nitzschia calliantha e P. pungens (até 7,3 x 104 células L-1), diatomáceas causadoras do envenenamento amnésico por consumo de molusco (ASP), foram correlacionadas com valores mais elevados de temperatura (de dezembro a abril), salinidade (>20) e concentrações de silicato (variando de 6,0 a 90,0 µM). A ocorrência destas diatomáceas na baía aparentemente depende do desenvolvimento de mecanismo de inoculação na água costeira adjacente e de seu subsequente transporte pelas correntes de maré para o interior do estuário. Durante o período de estudo, no entanto, a abundância celular de Pseudo-nitzschia permaneceu baixa, provavelmente devido à limitação do crescimento por falta de fosfato, especialmente na área externa. Além disso, espécies nocivas de Dinophysis, um dinoflagelado responsável pela produção de toxinas diarreicas (DSP), foram registradas em todas as campanhas mensais de amostragem. As maiores abundâncias de D. acuminata, D. caudata e D. tripos foram associadas com a camada logo acima da haloclina, nas regiões da baía onde a estratificação da coluna de água foi mais frequente. Em algumas ocasiões, a abundância de células de D.acuminata (até 3,2 x 103 células L-1) em áreas utilizadas para cultivo de moluscos bivalves para consumo humano, superou níveis considerados perigosos. Estes resultados indicam a necessidade de implantação de um programa de monitoramento de microalgas nocivas na Baía de Guaratuba.

This study investigated the spatial and temporal distributions of toxigenic phytoplankton species between October 2010 and April 2012 in Guaratuba Bay, Paraná state, Brazil, where aquaculture has been intensified in recent years. The highest abundances of Pseudo-nitzschia calliantha and P. pungens (up to 7.3 x 104 cells L-1), diatoms which cause amnesic shellfish poisoning (ASP), were correlated with higher values of temperature (from December to April, salinity (>20) and silicate concentrations (ranging from 6.0 to 90.0 µm). The occurrence of these harmful diatoms in the bay also appeared to depend upon the development of seeding mechanisms in the adjacent coastal water and its subsequent advection by tidal currents to the interior of the estuary. During the study period, Pseudo-nitzschia cell abundance remained low to moderate probably as a result of growth limitation by phosphate shortage, especially in the outer area of the estuary. In addition, harmful species of Dinophysis, dinoflagellates responsible for diarrhetic shellfish poisoning (DSP) events, were recorded in every sampling campaign. The highest abundances of D. acuminata, D. caudata and D. tripos were associated with the upper halocline layer in regions of the bay where water column stratification was more frequent. On some occasions, cell abundances of D. acuminata (up to 3.2 x 103 cells L-1) exceeded levels considered harmful in areas used to cultivate bivalve mollusks for human consumption. These novel results strongly indicate the necessity of implementing a monitoring program for harmful microalgae in Guaratuba Bay.

O complexo estuarino de Paranaguá (CEP; 25º30'S, 48º30'W), localizado no litoral sul do Brasil, abriga extensas áreas preservadas de manguezais e tem a pesca e aqüicultura como importantes atividades econômicas. Este trabalho investigou a ocorrência de microalgas nocivas no CEP e a presença de ficotoxinas no molusco bivalve Mytella guyanensis. Para tanto, foram coletadas amostras com periodicidade aproximadamente mensal, entre agosto de 2002 e outubro de 2003. Foram avaliadas variáveis físico-químicas, densidade de espécies nocivas e a presença de toxinas nos moluscos através de bioensaio com camundongos (DSP e PSP) e por cromatografia líquida (ASP). As espécies nocivas encontradas foram Pseudo-nitzschia spp., Dinophysis acuminata,Prorocentrum minimum,Gymnodinium catenatum,Phaeocystis spp., Chattonella spp. e Heterosigma akashiwo. Além dessas, Trichodesmium erythraeum e Coscinodiscus wailesii foram também incluídas no estudo pelo potencial de produzirem eventos nocivos na região. Toxinas diarréicas (DSP) foram detectadas em moluscos em dezembro de 2002 associadas à presença de D. acuminata (até 4.566 cel.l-1). Toxinas paralisantes e amnésicas foram produzidas por cepas cultivadas em laboratório. Primavera (de outubro a dezembro no hemisfério Sul) e final do verão (fevereiro a abril) foram os períodos de maior abundância de algas nocivas principalmente nos setores euhalino e polihalino interno do CEP.

The estuarine complex of Paranaguá - ECP (South Brazil, 25º30'S, 48º30'W) is a large subtropical system, where pristine mangrove forests are still present, and fishery and aquaculture are important economic activities. This work investigated the occurrence of harmful algae in Paranaguá Bay, as well as the presence of toxins in the filter feeding mussel Mytella guyanensis, a local fishery resource. Samples along the Paranaguá sub-system were collected almost monthly from August 2002 to October 2003. Besides physical and chemical variables, cell densities of harmful species and presence of toxins in the mussel by mouse bioassay (DSP, PSP) and HPLC (ASP) were performed. HAB species included Pseudo-nitzschia spp., Dinophysis acuminata,Prorocentrum minimum,Gymnodinium catenatum,Phaeocystis spp., Chattonella spp. and Heterosigma akashiwo.Trichodesmium erythraeum and Coscinodiscus wailesii were also included in this study due to their potential for harmful bloom formation. Toxin results showed the occurrence of DSP (December 2002) in shellfish related to the presence of D. acuminata (max. 4,566 cells.l-1). Additionally, cultivated strains produced paralytic and amnesic toxins in laboratory. Spring (October to December, Southern Hemisphere) and late summer (February to April) were the periods of higher abundance of harmful algae, mainly in euhaline and inner polyhaline sectors of the ECP.