What causes the amount of salt in the water of an estuary to change ?

the national environmental policy act (nepa) is a united states environmental law that promotes the enhancement of the environment and established the president's council on environmental quality (ceq). the law was enacted on january 1, 1970. to date, more than 100 nations around the world have enacted national environmental policies modeled after nepa.

it's anything that aren't producers and consumers.

explanation:

you've got to be clear on what "this" is