estuarythe tidal mouth of a large river where it meets the seaEstuaries are highly productive ecosystems that serve as nurseries for many fish species.NoteEstuaries are highly productive ecosystems that serve as nurseries for many fish species.Elon.io is an online learning platformWe have an entire course teaching IELTS Vocabulary — Band 7+ grammar and vocabulary.Start learning IELTS Vocabulary — Band 7+ now