King County's Beach Assessment

West Point Beach at Discovery Park, Seattle

Site Description

This beach is located in Discovery Park on both the north and south sides of the West Point Wastewater Treatment Plant. The north and south beaches are very different and are discussed separately.

South Beach

The gradient of this beach is very low. When the tide is at MLLW, more than a quarter mile of beach is exposed. Most of the beach lies at the base of a sand/clay bluff from which the beach material is eroded; consequently, the beach is very sandy. At about 0 feet, a large eelgrass bed begins. Closer to the shore, there are a few boulders and some cobbles. The sand forms a layer about 6 feet thick over cobbles and crushed rock used to build sludge lagoons, which have been dredged and dismantled.

North Beach

The beach here is more typical of the majority of the beaches in this region. On the point, the beach is relatively steep and is composed mainly of cobbles and gravel. However, as one proceeds east, the slope lessens and the beach becomes a flat composed of fine gravel and coarse sand. The upper beach here is stabilized with riprap. Near the flat area to the east, there is a deposit of concrete slabs that does not appear to have been disturbed for many years. Access to the beach has been limited to some extent for many years either by Metro or the Seattle City Parks Department.

Invertebrates

South Beach

Thirteen (13) species of invertebrates were found here. The horse clams seem to favor this kind of sandy environment over gravel. Since there is not much hard substrate for plants and animals to use for attachment, the diversity on this beach is relatively low. The boulders are colonized by barnacles, among which a few animals such as snails, chitons, colonial anemones and decorator crabs find shelter. The eelgrass bed is inhabited by Dungeness crabs, moon snails, cockles and burrowing anemones. Sea lemons, shaggy mice, and two sea slugs were also found here.

North Beach

The invertebrate population was surveyed and 29 species of invertebrates were found here, the ninth highest of the beaches surveyed. The population was particularly rich on and under the concrete slabs. As on most beaches, the mollusks and crustaceans were the best represented groups with fifteen and twelve species, respectively. The anemones seem to be well represented as well.

Snails		North	South
Sitka Periwinkle	Litorina sitchana		x
Checkered Periwinkle	Litorina scutulata		x
Direwhelk	Searlesia direa	x
Chitons
Lined Chiton	Tonicella lineata		x
Mossy Chiton	Mopalia mucosa		x
Hairy Chiton	Mopalia ciliata		x
Bivalves
Native Littleneck	Protothaca staminea	x	x
Manila Clam	Tapes japonica	x
Butter Clam	Saxidomus gigantea	x	x
Cockle	Clinocardium nutalli	x	x
Softshell	Mya arenaria		x
Horse Clam	Tresus sp.	x	x
Sand Clam	Macoma secta		x
Inconspicuous Macoma	Macoma inconspicua		x
Bay Mussel	Mytilus edulis		x
Jingle Shell	Posodesmus cepio		x
Sea Slugs
Sea Lemon	Archidoris monterreyensis	x
Shaggy mouse	Aeolidia papillosa	x
Sea Stars
Mottled Star	Evasterias troschelli		x
Purple Star	Pisaster ochraceus		x
Barnacles
Acorn Barnacle	Balanus glandula		x
Small Acorn Barnacle	Chthanalus dalli		x
Thatched Barnacle	Balanus cariosus	x	x
Crabs
Purple Shore Crab	Hemigrapsus nudus		x
Green Shore Crab	Hemigrapsus oregonensis		x
Black Clawed Crab	Lophopanopeus bellus	x	x
Dungeness crab	Cancer magister	x	x
Red rock crab	Cancer productus		x
Pygmy Rock Crab	Cancer oregonensis		x
Graceful Crab	Cancer gracilis		x
Porcelain Crabs
Pubescent porcelain crab	Pachycheles pubescens		x
Flattop crab	Petrolisthes eriomerus		x
Isopods
Brown Isopod	Idotea urotoma	x
Oregon Pillbug	Exosphaerona orgonensis	x

Clams

No formal clam survey was conducted, because volunteers would have gotten in the way of construction and landscaping activities at both the north and south beaches. No well defined clam band was observed on the south beach. The clam band on the north beach was very well defined.

Seaweed

There was no formal seaweed survey here, but Sargassum muticum was seen to be invading the area.

Other

Herons were common. A bald eagle was observed eating a fish it had caught and dragged onto the beach.

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Updated: 11/02/98