What is a key difference between marine and freshwater ecosystems?

The key difference between marine and freshwater ecosystems lies in salinity and nutrient availability. Marine ecosystems include oceans and seas that have high concentrations of salt, significantly influencing the type of organisms that can thrive there. In contrast, freshwater ecosystems such as rivers, lakes, and ponds have much lower salinity levels, making them suitable for a different set of aquatic organisms that are adapted to these conditions.

Salinity affects not only the types of species present but also the physiological processes of organisms. For example, saltwater species must be able to osmoregulate to cope with the higher salt concentration, while freshwater species have different adaptations. Nutrient availability can also differ between these ecosystems, with marine environments often being less nutrient-rich in open ocean areas, leading to distinct food web structures compared to the typically nutrient-rich freshwater bodies.

In summary, the distinction in salinity and nutrient availability is fundamental to understanding the ecological dynamics and biodiversity in marine versus freshwater ecosystems.