Browsing by Author "Churro, Catarina"
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- Detection of a Planktothrix agardhii Bloom in Portuguese Marine Coastal WatersPublication . Churro, Catarina; Azevedo, Joana; Vasconcelos, Vitor; Duarte Silva, AlexandraCyanobacteria blooms are frequent in freshwaters and are responsible for water quality deterioration and human intoxication. Although, not a new phenomenon, concern exists on the increasing persistence, scale, and toxicity of these blooms. There is evidence, in recent years, of the transfer of these toxins from inland to marine waters through freshwater outflow. However, the true impact of these blooms in marine habitats has been overlooked. In the present work, we describe the detection of Planktothrix agardhii, which is a common microcystin producer, in the Portuguese marine coastal waters nearby a river outfall in an area used for shellfish harvesting and recreational activities. P. agardhii was first observed in November of 2016 in seawater samples that are in the scope of the national shellfish monitoring system. This occurrence was followed closely between November and December of 2016 by a weekly sampling of mussels and water from the sea pier and adjacent river mouth with salinity ranging from 35 to 3. High cell densities were found in the water from both sea pier and river outfall, reaching concentrations of 4,960,608 cellsL(-1) and 6810.3 x 10(6) cellsL(-1) respectively. Cultures were also established with success from the environment and microplate salinity growth assays showed that the isolates grew at salinity 10. HPLC-PDA analysis of total microcystin content in mussel tissue, water biomass, and P. agardhii cultures did not retrieve a positive result. In addition, microcystin related genes were not detected in the water nor cultures. So, the P. agardhii present in the environment was probably a non-toxic strain. This is, to our knowledge, the first report on a P. agardhii bloom reaching the sea and points to the relevance to also monitoring freshwater harmful phytoplankton and related toxins in seafood harvesting and recreational coastal areas, particularly under the influence of river plumes.
- Distribution, identification and cytotoxicity of Gambierdiscus (Dinophyceae) in the Atlantic Selvagens Islands (Madeira, Portugal): a ciguatera gateway to EuropePublication . Godinho, Lia; Soliño, Lucia; Churro, Catarina; Timoteo, Viriato; Santos, Carolina; Gouveia, Neide; Diogène, Jorge; Reis Costa, PedroThe emerging threat of ciguatera poisoning (CP) in Europe has been associated with fish captured in the Canary Islands (Spain) and Selvagens Islands (Portugal). The first are heavily populated islands where numerous scientific studies have been carried out. Conversely, the Selvagens Islands are a nature reserve with low human pressure that have been rarely surveyed in terms of the marine benthic microalgae, including the epiphytic ciguatera-causing dinoflagellate species. To investigate the harmful microalgal diversity of the Selvagens Islands, a scientific cruise to these remote islands took place in September, 2018. The Gambierdiscus species composition and distribution, and the associated epiphytic dinoflagellate community, were assessed using artificial substrate devices. Gambierdiscus cells were found in all samples, reaching concentrations of up to 725 cells 100 cm(-2). G. australes was the only species identified after morphological and molecular analysis of the retrieved cultures. Species identification was confirmed by molecular characterization based on the LSU D8-D10 region. Nevertheless, phylogenetic studies indicated that some strains diverged from the G. australes clade suggesting genetic differentiation. Toxicity was estimated by neuro-2a cell-based assay in four strains, ranging from 2.46-83 fg of CTX1B eq. cell(-1). The epiphytic dinoflagellate community that co-occurred with Gambierdiscus comprised other toxic or potentially toxic dinoflagellates, such as Ostreopsis, Prorocentrum, Amphidinium and Coolia species. Oceanographic and meteorological data were also obtained to characterize the occurrence of Gambierdiscus. This study is the first stage in understanding the role of the Selvagens Islands in the incubation and proliferation of the ciguatera-causing dinoflagellates Gambierdiscus in the NE Atlantic.