Hi SR, ...well done..you've run a test and the results show that your algae didn't like a salt. Well, your algae is a kind of freshwater species then. However, the green algae (many species) either fresh or marine showed the adaptation to a wide range of salinity as well. In my area ..the Bay, some marine one can survived through the rainy flooding where the mass of freshwater from the channel empty to the Bay . Then later on this particular species thrive again when the salinity back to the normal range they prefer whereas the other doesn't cope with and die off. We can see the fluctuation of algal bloom in the Bay, up and down due to the growth limiting factors at a certain time. However, some algae species which is not a green one but red one i.e Dinoflagellate ..causes a "red tide"..that is toxic to aquatic wildlife...I don't know if this help you....sorry SR..