Final answer:
To survive in an estuary, plant species must have adaptations that allow them to tolerate salty conditions and obtain oxygen. For example, halophytic plants have filters in their roots to remove salt and can pump oxygen. Estuarine animals have behavioral adaptations to cope with changes in salinity, switching between anaerobic respiration and aerobic respiration.
Step-by-step explanation:
To successfully live in an estuary, a plant species must have an adaptation that allows it to tolerate salty conditions resulting from saltwater on their roots or from sea spray. Halophytic plants, which are adapted to deal with salinity, have filters in their roots to remove salt from water and some can pump oxygen into their roots. For example, estuarine plant species like mangroves have adapted aerial roots called pneumatophores that allow them to obtain oxygen from the air when submerged in water. In addition, estuarine animals like mussels and clams have developed behavioral adaptations to cope with changes in salinity. When exposed to low salinity, they stop feeding, close their shells, and switch to anaerobic respiration. When high tide returns and salinity increases, they open their shells, begin feeding, and switch back to aerobic respiration.