The researchers studied how different amounts of salt (NaCl) affected the growth and content of Haematococcus pluvialis algae. They found that low to medium salt levels increased the algae's biomass, but decreased protein content. Salt also reduced the amount of certain pigments in the algae, especially beta-carotene. However, salt led to higher levels of a beneficial pigment called astaxanthin. The algae produced more astaxanthin with 100 mM of salt. Salt also caused the algae to produce more reactive oxygen species (ROS), which are harmful molecules. Overall, salt had both positive and negative effects on the algae's growth and pigment production.