Detection of a Planktothrix agardhii Bloom in Portuguese Marine Coastal Waters
Laboratório de Fitoplâncton, Departamento do Mar e Recursos Marinhos, Instituto Português do Mar e da Atmosfera, Rua Alfredo Magalhães Ramalho, 6, 1449-006 Lisboa, Portugal
Centro Interdisciplinar de Investigação Marinha e Ambiental, CIIMAR/CIMAR, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos, 4450-208 Matosinhos, Portugal
Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4069-007 Porto, Portugal
Centro de Ciências do MAR, CCMAR, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
Author to whom correspondence should be addressed.
Academic Editor: Luis M. Botana
Toxins 2017, 9(12), 391; https://doi.org/10.3390/toxins9120391
Received: 3 October 2017 / Revised: 29 November 2017 / Accepted: 29 November 2017 / Published: 3 December 2017
(This article belongs to the Special Issue Selected Papers from the 5th Iberoamerican Cyanotoxins Meeting)
Cyanobacteria 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 cells·L−1 and 6810.3 × 106 cells·L−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.