What impact does increased salinity have on freshwater species?

Increased salinity can create significant challenges for freshwater species, which have adapted to thrive in low-salinity environments. Freshwater fish and plants typically maintain their internal saline balance through osmoregulation, a process that can be disrupted when they are exposed to higher salinity levels.

When salinity levels rise, freshwater species may experience physiological stress as their bodies struggle to maintain the proper balance of salt and water. This stress can lead to a range of negative effects, including impaired growth, reduced reproduction, and even mortality if the salinity levels exceed their tolerance thresholds.

In contrast, the other options suggest outcomes that do not align with the responses of freshwater species to increased salinity. Healthier growth and enhanced reproductive success would imply an advantageous condition, which is not the case for organisms that are not adapted to saline environments. Similarly, stating that increased salinity has no significant impact overlooks the well-documented biological stress that occurs in freshwater species when exposed to saline conditions.