Padilla Bay is an estuary at the saltwater edge of the large delta of the Skagit River in the Salish Sea. It is about eight miles long (north to south) and three miles across. In 1980, this bay was selected to be included in the National Estuarine Research Reserve System.
Because the bay is filled with sediment from the Skagit River, the bottom is very shallow, flat, and muddy. It is so shallow that almost the whole bay is intertidal. This means that it is flooded at high tide but when the tide goes out the whole bay empties out, exposing miles and miles of mud flats. This condition allows unusually large eelgrass meadows to grow. There are nearly 8,000 acres of eelgrass in Padilla Bay. Click here to see a habitat map (simple version, 16KB) (more detailed version, 2.5MB).
Eelgrass is valuable because it is habitat for wildlife and commercially harvested animals. Eelgrass is used as a nursery by salmon, crab, perch, and herring. Eelgrass is also home for millions of worms, shrimp, clams, and other invertebrates that are food for great blue herons, eagles, otters, seals, as well as humans. This is why Padilla Bay was selected to be a National Estuarine Research Reserve.