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Estuary


Where the freshwater of the Nisqually River meets the salt water of the Puget Sound, a rich habitat called an estuary is created. Estuaries provide rich nutrients and sediment for plants, animals and invertebrates. Twice each day, the high tide floods the estuary with water and twice each day the low tide drains the area of water. The Refuge has restored 762 acres of the Nisqually estuary by removing dikes and introducing tidal waters after an absence of more than 100 years. In the estuary there are several distinct habitat types that are described below.

Salt Marsh, Sloughs, and Channels of the Estuary

The Nisqually estuary has both high and low salt marsh. Salt marshes are areas of slightly higher elevation and covered with water only during high tides. The low salt marsh (lower elevation) will be covered with water most of the time during high tides. The high salt marsh (higher elevation) will only be covered during very higher tides. Plants and animals that live in the salt marsh must adapt to handle salt water. Some examples are the Puget Sound gumweed and pickleweed, which sweat out salt through evaporating pores in their leaves. This process deposits a salt film or dusting on the leaves. Sloughs and channels on the estuary provide habitat and food for salmon fry before they head out to the Sound, as well as adults returning to spawn. These fish provide food for birds such as great blue heron, hooded merganser and grebes.
 

Birds: Grebes (various species), Great Blue Heron, Common Merganser, Caspian Tern, Glaucous-winged Gull, Bufflehead

Animals/fish: Clams, Crab, Amphipod, Salmon, Steelhead, Lugworm

Plants: Puget Sound Gumweed, Lyndbys Sedge, Tufted Hairgrass, Pickleweed

Mudflats on the Estuary

The Nisqually River and McAllister Creek continually drop sediment on some 1,000 acres the mudflats. This area is rich in invertebrates, including worms, clams and crustaceans (crabs). One square yard of mudflats can contain 100 clams, 2,000 worms and 30,000 amphipods! During spring and fall migrations shorebirds gather to feed on this wealth of invertebrates.
 

Birds: Western Sandpiper, Dunlin, American Wigeon, Greater Yellowlegs

Animals/fish: Amphipod, Threadworm, Midge Larvae, Clam, Snail, Sculpin

Plants: Sea Lettuce, Phytophankton

Last Updated: Aug 17, 2012
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