Morphology, phylogeny, growth rate and nodularin production of Nodularia spumigena from Brazil

ABSTRACTBlooms of the toxic cyanobacterium Nodularia spumigena occur in various locations worldwide, but have not been observed in Brazil until recently. Three Nodularia strains were isolated from summer blooms in experimental shrimp production ponds of Penaeus vannamei in Rio Grande, in southern Brazil; these strains were characterized by morphology, phylogeny, growth rate and toxicity. The strains were identified as N. spumigena based on the size of vegetative cells, heterocytes and akinetes under a light microscope and based on the number of gas vesicles per μm2 under a transmission electron microscope. The 16S rRNA gene sequences of the three strains showed high identity (> 99%) with N. spumigena sequences available on the NCBI database but were grouped closer in the phylogenetic tree with N. spumigena strains from Australia and USA than those from the Baltic Sea. The growth rate in batch culture varied between 0.2 and 0.6 μ d−1 based on cell density, optical density and chlorophyll-a content. The thr...