Detection of a Planktothrix agardhii Bloom in Portuguese Marine Coastal Waters.

Catarina Churro,Vitor Vasconcelos,Joana Azevedo,Alexandra Silva

doi:10.3390/toxins9120391

Catarina Churro, Vitor Vasconcelos + Show 2 more

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https://doi.org/10.3390/toxins9120391

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Abstract

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.

Highlights

In Portugal, the reports of freshwater cyanobacterial blooms in estuaries were related with the cyanobacterium Microcystis
We found that the bloom-forming cyanobacterium Planktothrix agardhii is reaching sea waters at high cell concentrations and that the surrounding area at the land-sea interface is heavily loaded with P. agardhii cells
The cell densities found in the water, from the river outfall, beach and sea were above the cell limit of 2 × 106 cells·L−1 recommended by WHO, from which microcystin concentration in water can exceed the WHO guideline of 1 μg·L−1 of safe daily ingestion by an oral root [3]

Summary

Introduction

Toxic cyanobacterial blooms have long been a recognized threat to freshwater ecosystems and human health, and their negative impacts have been reported and reviewed extensively [1,2,3,4,5,6,7].These toxic proliferations are still a major concern in freshwater lakes and reservoirs and their complexity and unpredictable nature continue to challenge researchers and monitoring authorities [8].Toxins 2017, 9, 391; doi:10.3390/toxins9120391 www.mdpi.com/journal/toxins oxins 2017, 9, 12ccurrence, magnitude, and persistence of theseoccurrence, blooms are distribution, perceived to magnitude, be increasing and persistence of these blooms are pe Toxins distribution, 2017, 9, 12 of 13Theyears occurrence, distribution, magnitude, persistence of these blooms are global perceived to been be increasing lobally over the last [8,9,10,11,12,13] and have been related toand increasing globally over human the last activities years and [8,9,10,11,12,13]and have related to increasing hum globally over the last years and have been related to increasing human activities proliferations and global warming [9,10,11,12,13,14]. Theyears occurrence, distribution, magnitude, persistence of these blooms are global perceived to been be increasing lobally over the last [8,9,10,11,12,13] and have been related toand increasing globally over human the last activities years and [8,9,10,11,12,13]. Juncture of several factors, occurrence relatedisarebut the not resultexclusive of theand to, juncture several factors, related globally the lastof years and cyanobacterial have been related to increasing human activities global is the result of inputs, thecyanobacterial juncture of several related but not exclusive to,inputs, increasing/reduction ncreasing/reduction of nutrient increasing river factors, barriers, increasing/reduction increased water of nutrient stratification increasing river barriers, increa warming [9,10,11,12,13,14].

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