Effects of Salinity and Temperature on the Growth, Toxin Production, and Akinete Germination of the Cyanobacterium Nodularia spumigena

Abstract

Harmful blooms of the cyanobacterium Nodularia spumigena occur in several parts of the world, and this species is notorious for its ability to produce cyanotoxins, such as nodularin. This species is also able to perform akinete differentiation, thus favoring the success of their populations under adverse conditions. In southern Brazil, N. spumigena has developed large blooms in experimental shrimp production farms. In this study, we implemented an experiment to evaluate the influence of salinity and temperature on several physiological attributes of a Brazilian strain of N. spumigena: cell growth, nodularin production, the ability to form akinetes and germination potential. A factorial experiment (3 × 4) was conducted to test the effects of temperature (15, 23, and 30 • C) and salinity (1, 7, 15, and 30 ppm) on the growth, production of nodularin and the differentiation of akinetes. The germination potential of the akinetes was tested after incubation for 30, 60, 90, 120, 180, and 360 days at 4 • C in the dark. N. spumigena grew under a wide range of salinity and temperatures, but salinity had a greater influence. The highest cell densities at the temperatures tested were observed at salinity 7 ppm and the lowest at salinity 1 ppm. The toxin nodularin was produced in all treatments, but there was an inverse relationship between the content of nodularin per cell and cell density. The akinetes were also differentiated in all the treatments, with the exception of S1T30. However, the largest proportion of akinetes (65% of the cells) was observed in the treatment with low cell growth at salinity 15 and 15 • C, possibly indicating an effort of the population to survive over the long term. The akinetes germinated in all treatments, but those cultivated at salinity 7 and 15 ppm (except S15T30) showed a higher percentage of germination and, in contrast, the lowest germination rate was observed in the treatments with salinity 1 ppm. Thus, the low salinity (1) at all the temperatures tested has the potential to inhibit N. spumigena blooms, since it hampers cell growth and the formation of akinetes.

Factors Driving Bacterial Microbiota of Eggs from Commercial Hatcheries of European Seabass and Gilthead Seabream

“…Since the broodstock water in sites 2 and 3 had a lower temperature (mean ∼ = 16 • C) and salinity than site 1, environmental conditions including these two factors may explain the higher abundance of Cyanobacteria in these sites. Studies characterizing the growth and physiology of Cyanobacteria have demonstrated that temperature and salinity directly influence their growth [42]. Corroborating evidence for the importance of salinity on fish-associated microbiota also comes from studies of the skin-associated microbiota in Atlantic salmon (Salmo salar) transitioning between fresh and saltwater.…”

A Mini Review on Microcystins and Bacterial Degradation

“…WHO [1] reported that blooms of toxic cyanobacteria are gradually increasing worldwide in both frequency and severity. While cyanobacterial blooms occur naturally in water bodies, the combination of environmental factors such as nutrients (nitrogen and phosphorus), weather conditions, carbon dioxide, water body, salinity, sunlight, pH, heavy metals, brief periods of drought and heavy rain may trigger for the proliferation of the blooms [2][3][4][5][6]. Cyanobacterial blooms have become a serious global environmental problem in both developing and developed countries due to the unpleasant odor, taste and cyanobacterial toxins produced.…”

Genomic and Metabolomic Analyses of Natural Products in Nodularia spumigena Isolated from a Shrimp Culture Pond

“…Although cyanobacteria naturally compete with algae in aquaculture tanks, cyanobacteria often dominate eutrophic tanks due to their higher ability to thrive with low dissolved oxygen, high temperature, and turbidity [56]. Moreover, the water salinities commonly used in shrimp ponds are optimal for N. spumigena growth [49,[57][58][59]. Therefore, cyanobacteria may form blooms in these environments and negatively interfere with shrimp production [60].…”