Thermal niche of the dinoflagellate Karlodinium veneficum across different salinity and light levels.

This article focuses on the interactive effects of temperature, salinity, and light on the growth, thermal niche, and cellular carbon and nitrogen content of the harmful dinoflagellate Karlodinium veneficum in the Chesapeake Bay. Laboratory experiments showed that K. veneficum growth is highest at temperatures of 25–28°C, salinities of 10–20, and high light conditions, which align with in situ bloom occurrences predominantly at 25–29°C and salinity 10–14. The study found that higher light intensities increased thermal sensitivity and lowered optimal growth temperatures, while cells at higher salinity (30) exhibited greater thermal tolerance, suggesting that lower bay regions may serve as over-summering habitats. These findings imply that warming above 28°C may suppress bloom formation, but mixotrophic feeding behavior and habitat variability could modulate bloom dynamics under future climate scenarios.