4. which aquatic ecosystem typically forms along coastlines where fresh water and salt water meet, leading to varying degrees of salinity?

I would say estuary, because that's where a fresh water river and an ocean meet, and that leads to a transition between salt to fresh water.

The virus is considered to be are living item since they have hereditary material dnas or rnas. they can imitate and change. they respond to boosts, for example, radiation, chemicals, and warmth. they have antigenic properties. they are proficient to duplicate with a same hereditary constituent.