Over time, saltwater is replaced by freshwater. Freshwater barrier ponds are located throughout the coastal zone of Atlantic Canada. Every province in Atlantic Canada has several significant freshwater barrier ponds. The life found in a freshwater barrier pond will vary depending on the salinity level. Snails, clams, and mussels are abundant in freshwater.
Molluscs live in the sediments of the pond and on aquatic plants.
The fish that are most successful in brackish water can adapt to varying degrees of salinity, temperature, and oxygen. Freshwater barrier ponds can be greatly affected by human activities. If an ecosystem close by is altered in any way it can have detrimental effects on the pond. Freshwater barrier ponds provide a unique opportunity to further understand how coastal ecosystems interact with one another. Unfortunately, they are the least well understood and the least studied of all the ecosystems of the coastal zone of Atlantic Canada.