Assessment of nitrogen interaction with temperature on the growth and toxin production of mat-forming toxin-producing Anagnostidinema carotinosum.

Aims: Global warming and eutrophication contribute to the severity of cyanobacteria blooms. However, it is unclear how these factors influence the growth and toxin production of Anagnostidinema carotinosum.
Methods and Results: Based on morphological and molecular analysis, this is the first time A. carotinosum was identified in South Korea. The interactive effect of temperature (25, 30 or 34°C) and nitrogen (2.5, 3.5 or 4.5 mg NO ₃ -N l ^-1 ) on A. carotinosum growth and toxin production was studied. Increasing nitrogen limitation reflects reduced growth and chlorophyll-a content at all temperatures. However, the growth was effective under nitrogen limitation when temperatures exceeded 25°C. The maximum growth was found at 30°C, followed by 34°C under higher nitrate levels (3.5 and 4.5 mg l ^-1 ). In addition, the cell microcystin and anatoxin-a quota increased significantly at 25°C with increasing nitrate limitation, decreasing considerably at 30°C in the same nitrate gradient.
Conclusion: These results suggested temperatures stimulate A. carotinosum growth at 30 and 34°C and cellular toxin quota at 25 and 34°C with increasing NO ₃ -N levels.
Significance and Impact of the Study: These findings imply that limiting nitrogen input alone can effectively reduce biomass; however, controlling A. carotinosum and its toxins at higher temperatures under nitrate limitation is necessary for water quality.
(© 2022 Society for Applied Microbiology.)