AUTHOR=Viana Tatiana V. , Fistarol Giovana O. , Amario Michelle , Menezes Rafael B. , Carneiro Beatriz L. R. , Chaves Daisyane M. , Hargreaves Paulo I. , Silva-Lima Arthur W. , Valentin Jean L. , Tenenbaum Denise R. , Arruda Edilson F. , Paranhos Rodolfo , Salomon Paulo S. 

TITLE=Massive Blooms of Chattonella subsalsa Biecheler (Raphidophyceae) in a Hypereutrophic, Tropical Estuary—Guanabara Bay, Brazil

JOURNAL=Frontiers in Marine Science

VOLUME=6

YEAR=2019

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2019.00085

DOI=10.3389/fmars.2019.00085

ISSN=2296-7745

ABSTRACT=<p>Cell concentrations of the potentially harmful raphidophyte <italic>Chattonella subsalsa</italic> Biecheler were quantified in surface waters of Guanabara Bay, a heavily eutrophicated estuarine system in tropical Brazil, from February 2014 to January 2018. Cells were imaged and quantified in live samples by means of an automated imaging system (FlowCam®). Bloom episodes (&gt;0.1 × 10<sup>6</sup> cells L<sup>−1</sup>) were observed in 37 samples, mostly in a shallow (&lt;10 m) area with extremely high nutrient and organic matter loads (average total <italic>P</italic> = 19 μM and total <italic>N</italic> = 344 μM), intermediate salinity (average 24.5), and low water transparency (average Secchi depth = 0.54 m) due to continental runoff. Blooms in this area reached up to 13.3 × 10<sup>6</sup> cells L<sup>−1</sup>. <italic>C. subsalsa</italic> cell concentration was correlated with parameters linked to eutrophication of the bay. On a monthly basis, <italic>C. subsalsa</italic> abundance was correlated with a period of positive Multivariated El Niño/Southern Oscilation Index (MEI) that lasted from the beginning of 2015 to mid-2016 (known as Godzilla El Niño), indicating a potential influence of regional climate on the occurrence of <italic>C. subsalsa</italic>. Notably, at least six fish kill episodes were reported in the Bay during this period which, added to the toxicity of <italic>C. subsalsa</italic> strains isolated from the bay to <italic>Artemia</italic> nauplia (48h-LC<sub>50</sub> = 7.3 × 10<sup>6</sup> cells L<sup>−1</sup>), highlights the threat that this HAB species poses to the environment. This is the first report of recurrent, massive <italic>C. subsalsa</italic> blooms in Guanabara Bay. Regardless of the influence of climatic forcing in favoring <italic>C. subsalsa</italic> development, reducing nutrient loads would be the best strategy to mitigate blooms of this and other potentially harmful algae in Guanabara Bay.</p>