King County's 1996/1997 Beach Assessment

Lincoln Park, Seattle

Site Description

Lincoln Park is the oldest and one of the larger Seattle City parks. The park is located in West Seattle a short distance north of the Fauntleroy ferry dock and it occupies most of Williams Point. The beach is about a mile long and is stabilized by a sea wall for the entire length. The beach on the south side of the point undergoes constant erosion and has had beach materials replaced by the U.S. Army Corps of Engineers several times in the past, most recently in 1994. The beach at the south end of the north section is very sandy and steep. Rather than being concave in cross-section, the beach is nearly flat. Local residents stated that this sand originated on the south beach and has been washed around the point. That beach drift explains why the south beach requires re-nourishment periodically.

Because the beach is continuous around the point, the north and south beach sections are subject to very different wave actions and the beach dynamics. The upper beach on the south side is composed mainly of the washed gravel used to re-nourish the beach down to about the +2' level. Northward, the beach becomes more cobbled and concave with a few very large boulders at about the +2' level. Below that, the beach becomes flatter and sandier and, eventually, eelgrass beds appear.

Invertebrates

South Beach

Thirty-one (31) invertebrate species were found here, the fourth lowest of the 13 beaches surveyed. Most of the animals found on the south beach were also found on the north beach. The diversity on this beach was in the mid-range of the beaches, but it contained some relatively uncommon species such as the burrowing anemone and native oyster. Mottled sea stars and graceful decorator crabs were common, as was the red rock crab. Looking down the length of the beach as the tide receded, clam squirts appeared to be continuous, which was surprising given evidence of heavy harvesting.

North Beach

Forty-six (46) species of invertebrates were identified on this beach, the third most diverse of the beaches surveyed. The diversity of crabs is notable: red rock crab, Dungeness crab, graceful crab, Lophopanopeus bellus (black-clawed crab), purple shore crab, Pugettia gracilis (graceful kelp crab), northern kelp crab, and yellow shore crab were found. Solaster stimpsoni (sun star), the beach assessment project logo, was observed. Three species of sea cucumbers were found during the survey. Two species of porcelain crabs were common, Petrolisthes cinctipes (flat porcelain crab) and P. eriomerus (flattop crab). Mottled sea stars, purple sea stars, and red sea cucumbers were common near the boulders, and long-armed brittle stars were easy to find under the larger rocks.

Limpets		North	South
Plate Limpet	Acmaea scutum	X	X
Variegated Limpet	Acmaea persona	X	X
Shield Limpet	Acmaea pelta	X	X
Finger Limpet	Acmaea digitalis	X	X
Snails
Sitka Periwinkle	Litorina sitchana	X	X
Checkered Periwinkle	Litorina scutulana	X	X
Moon Snail	Polinices lewisi	X	X
Fringed Dogwinkle	Thais lamellosa	X	X
Half-slipper shell	Crepipatella lingulata	X
Chitons
Lined Chiton	Tonicella lineata		X
Mossy Chiton	Mopalia mucosa		X
Woody Chiton	Mopalia lignosa	X	X
Black Katy	Katharina tunicata	X	X
Bivalves
Native Littleneck	Protothaca staminea	X	X
Manila Clam	Tapes japonica	X
Butter Clam	Saxidomus gigantea	X	X
Cockle	Clinocardium nutalli		X
Horse Clam	Tresus sp		X
Inconspicuous Macoma	Macoma inconspicua	X
Bent Nose Macoma	Macoma nasuta		X
Bay Mussel	Mytilus edulis	X	X
Horse Mussel	Modiolus rectus		X
Geoduck	Panope generosa		X
Jingle Shell	Posodesmus cepio		X
Native oyster	Ostrea luridea	X	X
Sea Stars
Mottled Star	Evasterias troschelli	X	X
Sun Star	Solaster stimpsoni	X
Purple Star	Pisaster ochraceus	X
Serpent Star
Long Armed Brittle Star	Amphiodia occidentalis	X
Sea Cucumbers
White	Eupentacta quinquesemita	X
Orange	Cucumaria miniata	X
Barnacles
Acorn Barnacle	Balanus glandula	X	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	X
Black Clawed Crab	Lophopanopeus bellus	X
Graceful kelp crab	Pugettia gracilis	X
Northern kelp crab	Pugettia producta	X
Red rock crab	Cancer productus	X	X
Commensal crab
Burrowing pea crab	Scleroplax granulata	X
Hermit crabs
Hairy hermit	Pagurus hirsutiusculus		X
Porcelain crabs
Thick claw porcelain crab	Pachycles rudis	X
Pubescent porcelain crab	Pachycheles pubescens	X
Anemones
Colonial anemone	Anthopleura elegantisima		X
Green anemone	A. xanthogrammica	X	X
Burrowing anemone	A. artemisia		X
Hydroids	unidentified	X
Segmented worms
Corrugated worm	Glyseria	X
Shellbinder worm	Thelepus crispus	X
Scale worm	Halosydna sp.	X
Irridescent worm	Hemipodus borealis	X
Sand worm	Nereis virens	X
Tube worms
Calcareous tubeworm	Serpula vermicularius	X
Flatworms
Large speckled	Kaburakia excelsia	X
Small speckled	Freemania sp.	X
Isopods
Beach Cockroach	Ligia pallasii	X	X
Amphipod
Skeleton Shrimp	Caprella kennerlyi	X

Clams

South Beach

The clam band here is not continuous; it is separated by a shallowly buried layer of clay. There are two distinct sections: one between the south end of the beach and 300 feet, the other from 900 feet from the south end to 1,600 feet, but they will be discussed together. They cover about 2.3 acres but the distribution of the clams is somewhat spotty. The population density of eight clams per square foot was the second lowest of all of the beaches.

Of the 41 holes dug, 25 contained at least one clam. Numerically, the littleneck, macoma and butter clams dominated the population here with 45%, 28% and 20% respectively. By weight, the population was dominated by the littleneck clams (47%), butter clams (36%) and horse clams (9%).

Check out the following graphs for more information about the clam population on the south beach:
Numeric composition of clam population
Weight composition of clam population


One hundred and ninety-two (192) clams were collected weighing 4026 grams, total. The average weight was 21 grams per clam, the highest for all of the beaches. There are relatively few clams overall, but they tend to be large. One explanation is that harvesters have selected the most easily accessible species, which tend to be located in the first three inches, and are smaller.

Thirty-eight (38) of the 64 (59%) littleneck clams were legal and 22 of the 32 (or 69%) of the butter clams found were legal size. This was the second highest for the beaches surveyed. No manila clams were found. The littleneck and butter clams here were somewhat larger than the average for all of the beaches; the cockles and horse clams were about twice the average and the macoma clams were about five times the average for all beaches.

North Beach

The clam band along this beach is extremely narrow. The high percentage of cobbles in the substrate may limit the density of the clam population on this beach. The band is about 800' long but is less than 40' wide in most places. While clams were found all along this strip, most came from an area 400' long which lays between 800' and 1200' west of the north end of the beach. Neither Manila nor soft-shell clams were found on this beach. Numerically, the littleneck (47%), butter and macomas (24% each) dominated the samples. The butter clams contributed most of the weight (40%) and the littleneck clams contributed 36%. One hundred and thirty-six (136) clams, found in the 12 holes dug, weighed more than 4605 grams, total. The average clam on this beach weighed 34 grams, the highest for all beaches; the yield was estimated to be 383 grams per square foot, the second highest for all of the beaches surveyed. The littleneck, butter, and horse clams found on the north beach weighed about twice as much as the averages for all beaches, while macoma clams were about the same as the average.

Check out the following graphs for more information about the clam population on the north beach:
Numeric composition of clam population
Weight composition of clam population


Forty-eight (48) of the 80 (60%) of the littleneck clams collected were of legal size-the highest percentage of all of the beaches. Nineteen (19) of 36 of the butter clams, or 53%, were legal.

Seaweed

South Beach

There was no formal survey of the algae here, but several varieties were mentioned in the field notes. Punctaria and Smithora were found growing on the eelgrass. Sugar kelp, Costata sp., Iridea, nori and P. lanceolata, Rockweed, Microcladia, Desmarestia sp., Ceramium sp. and Nereocystis luekeana (bullwhip kelp) were also noted.

Green (Chlorophyceae)

Ulva lactuca

Brown (Phaeophyceae)

Desmarestia intermedia

Desmarestia munda

Fucus sp.

Hedophyllum sessile

Laminaria saccharina

Leathesia difforimis

Nereocystis leutkeana

Pylaiella littoralis

Ralfsia sp.

Sargassum muticum

Red (Rhodophyceae)

Agardhiella tenera

Cryptosiphonia woodii

Gigartina cristata

Gigartina exasperata

Gigartina latissima

Grateloupia californica

Hymena sp.

Iridea cordata

Microcladia coulteri

Polyneura sp.

Polysiphonia collinsii

Porphyra lanceolata

Porphyra perforara

Prionitis lanceolata

Pterosiphonia bipinnata

Rhodymenia palmata

At the south boundary of the beach, cobbles are more common, as are the large brown algae that attach to them. Near the point, a large sand spit extends to the southwest for a 100 yards or more. In deeper water nearby, there is a bull kelp bed. Along the shore on the south end of the point, there is a very large bed of sweet kelp that has drastically diminished over the past two years. The harvesting of these algae at nearly commercial levels, which has been observed on more than one occasion, may account for the decline. For instance, kelp, being dried, covered over a 100 feet of drift-wood.

Sargassum is very common on the south beach, although it was not reported in any significant quantity by Thom during his survey of this beach in the 1970s. It is now on both beaches, but there is more on the south beach.

North Beach

Twenty-six (26) species of algae from this beach were identified. That is the highest number for all of the beaches surveyed. The red algae dominated the beach (16 species), the brown algae were subdominant (nine species) including Sargassum and one green specie, sea lettuce, was found. There is a long bed of bullwhip kelp offshore from the clam bed.

Near the 4,000 foot transect (starting from the south end of the beach), the rocks on the lower beach are nearly covered by red algae such as Porphyra sp., Iridea sp., Gigartina esasperata (Turkish towel), Grateloupia sp. and Prionitis sp. Nori is common on the upper beach here.

Other

There is no north/south beach differentiation in the bird surveys. The birds were surveyed in 1994 and again in 1996. Forty-seven (47) bird species were found on the beach or a short distance offshore. Some of the birds appear to by year-round residents (western gull, northwest crow, great blue heron). Others were apparently migrants between freshwater bodies during the summer and saltwater during the winter. such as the common goldeneye, Barrow's goldeneye, bufflehead and the hooded merganser. American widgeons, which can appear in the area in huge flocks, were observed. A large pod of dolphins were observed here in the spring, as were harbor seals.

Use

The difference in accessibility to these two beaches accounts for the differences in the amount and diversity of intertidal life on these beaches. The south end is easily accessed by both harvesters and herds of school children in mid-June near the end of the school year; consequently, there are fewer clams to be collected here and the diversity is much lower than on the north end.

The most noticeable difference between the habitats on the two beaches is that all of the larger rocks on the south beach have been overturned at least once. In the north beach, the rocks appear undisturbed, and only a few craters have been left by clam harvesters. At the south beach, parking is within a few hundred feet of the beach; at the north beach one must park a half mile away.

The large kelps are being removed from sections of the beach and might not survive the harvesting pressure without vigilant monitoring by enforcement personnel.

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Updated: 11/02/98