As the Chesapeake expanded north and west, the Rhode River sub-estuary was formed. An estuary is a semi-enclosed body of water with sources of both fresh and salt water. Estuaries have access to the ocean, so they are influenced by the tides. Salt water enters the Chesapeake Bay from the Atlantic Ocean, while fresh water comes primarily from rivers such as the Susquehanna, Potomac, and the James. The Rhode River sub-estuary receives salt water from the Bay and a large portion of its fresh water from Muddy Creek.
Estuaries are extremely productive ecosystems.
Nutrients such as Nitrogen and Phosphorus are transported by water running off the land from agricultural fields. Plants growing in the shallow waters of an estuary use the sun's energy to convert these nutrients into food through photosynthesis. These plants become food for small animals which then become food for larger animals. It is this abundant food resource which brought the earliest inhabitants to this area. They also gathered berries, nuts, and seeds.