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

Abstract

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. 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 4.5mg NO3 -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 4.5mg 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. These results suggested temperatures stimulate A. carotinosum growth at 30 and 34°C and cellular toxin quota at 25 and 34°C with increasing NO3 -N levels. 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.