King County's 1996/1997 Beach Assessment

Richmond Beach Park, Shoreline

Site Description

The surveyed section of this beach was that which lay within the Richmond Beach, King County Park, in the north-west corner of King County. It is about a mile south of Point Wells. The beach is L-shaped and is about 1,300 feet long. The west-facing section is quite steep and the surface during the summer is very sandy (see contour map). There are a few patches of gravel overlaid by 3 to 6 feet of sand which the horse clams find attractive. The cockles prefer the sand and the small eelgrass beds offshore.

The point is not as steep and is composed primarily of cobbles. On the upper beach, the cobbles are loose because the surf washes out the sand and gravel. The cobbles are loose and they rattle when one walks on them. The cobbles on the beach below that are mixed with sand and gravel, providing a habitat for horse clams and butter clams.

East of the point, the beach is composed of smaller grained material, although it is steep. That beach abruptly becomes a sand flat that supports some eelgrass.

There is some evidence of erosion on this beach; the ends of some pilings, which were flush with the surface of the sand a few years ago, now protrude one to 2 feet above the beach.

It appears that the sediments on the beach move during the winter months: consequently, there is a limited clam population here.

Invertebrates

Thirty-seven (37) species of invertebrates were found during the formal survey of this beach. That diversity was ranked fifth highest for the 14 beaches surveyed. More mollusks were identified than any other phylum. The mollusks included three species of limpets, two snails, two chitons, five bivalves, and three nudibranchs. Large flatworms, both Kaburkia sp. and Freemania sp., were common. The rocks near the 0 foot level provide suitable habitat for a variety of mollusks such as: chitons, sea slugs, limpets and jingle shells.

Lynwood Smith, author of Common Seashore Life of the Pacific Northwest assisted with our survey of this beach.

Limpets
Plate Limpet	Acmaea scutum
Variegated Limpet	Acmaea persona
Finger Limpet	Acmaea digitalis
Snails
Sitka Periwinkle	Litorina sitchana
Checkered Periwinkle	Litorina scutulata
Chitons
Mossy Chiton	Mopalia mucosa
Woody Chiton	Mopalia lignosa
Bivalves
Cockle	Clinocardium nutalli
Softshell	Mya arenaria
Horse Clam	Tresus sp.
Inconspicuous Macoma	Macoma inconspicua
Bay Mussel	Mytilus edulis
Sea Slugs
Rough Mantled Doris	Onchidoris bilamellata
Sea Lemon	Archidoris monterreyensis
Shaggy mouse	Aeolidia papillosa
Sea Stars
Mottled Sea Star	Evasterias troschelli
Purple Sea Star	Pisaster ochraceus
Brittle Stars
Long Armed Brittle Star	Amphiodia occidentalis
Sea Cucumbers
Orange	Cucumaria miniata
Urchin
Green Urchin	Strongylocentrotus droebachiensis
Barnacles
Acorn Barnacle	Balanus glandula
Thatched Barnacle	Balanus cariosus
Crabs
Black Clawed Crab	Lophopanopeus bellus
Graceful decorator crab	Oregonia gracilis
Red rock crab	Cancer productus
Anemones
Colonial anemone	Cribrina elegantisima
Green Anemone	Anthopleura xanthogrammica
Hydroids
Segmented worms
Corrugated worm	Glyseria
Scale worm	Halosydna
Irridescent worm	Hemipodus borealis
Sand worm	Nereis virens
Tube worms
Calcareous tubeworm	Serpula vermicularius
Flatworms
Large speckled	Kaburakia excelsia
Small speckled	Freemania
Nemerteans
Green nemertean	Emplectonema gracile
Isopods
Oregon Pillbug	Exosphaerona orgonensis
Brown Isopod	Idotea urotoma

Clams

The clam band here is apparently very small; only eighth of 22 holes dug contained one or more clams. The three-quarter acre clam bed here is the smallest estimate among the 14 beaches surveyed. There are essentially two habitats available for colonization by the clams: sand flats, which are too mobile to support a large population, and wave-swept cobbles and boulders from which the spat are routinely washed during the winter storms.

Numerically, horse clams dominated the population (69% of the 73 clams) but because they were mostly small, they only represented 22% of the biomass. Numerically, butter clams made up 19% of the population and 11% of the biomass. The statistical impact of large individuals on the averages of small populations is shown by contrasting numbers with biomass. Cockles represented only 1% of the population, which, in a population of 73, means one cockle. That one cockle weighed about 200 grams and made up 46%, nearly half, of the biomass.

The 73 clams found weighed 442 grams (a 6.1 gram average). That average is the fourth lowest average for all of the beaches. Without the large cockle, the average would be about 3.2 grams each. The population density of nine clams per square foot and biomass density of 54 grams per square foot were fourth lowest as well.

Check out the following graphs for more information about the clam population:
Numeric composition of clam population
Weight composition of clam population
Numeric distribution of clam population
Biomass distribution of clam population

There were very few legal-sized clams on this beach. Only one of the five manila clams was of legal size, the native littleneck was not and only two of 14 butter clams were of legal size.

It appears that the horse clams and butter clams do better here because they live deeper in the substrate and survive the winter storms. Their long siphons help them survive being buried periodically by the shifting sands.

Seaweed

Seventeen (17) species of marine algae were identified here, ranking it fourth among the eight surveyed. There were four species of green algae, five of red (including Nori,) and the brown algae (Phaeophyta), were the represented by eight species including sargassum, the invasive algae from Asia. There is a green "fuzz" on many of the cobbles at about the +3' level and below. Since they resemble 3 mm. bright green tubes, it is presumed that the fuzz is some species of Enteromorpha.

Green (Chlorophyceae)

Cladophora sp.

Enteromorpha intestinalis

Enteromorpha linza

Ulva lactuca

Brown (Phaeophyceae)

Costaria costata

Fucus sp.

Hedophyllum sessile

Leathesia difforimis

Nereocystis leutkeana

Petalonia debilis

Punctaria hesperia

Sargassum muticum

Red (Rhodophyceae)

Ceramium pacificum

Gigartina latissima

Iridea cordata

Porphyra perforara

Smithora naiadum

Other

The nest of an intertidal fish, called a midshipman, was found in a cavity under a rock. The bright yellow eggs were attached to the bottom of the rock in a spiral arrangement and a ten-inch adult stayed in the cavity to protect them. Tide pool sculpins were also common here.

Use

While this beach is not much used for harvesting, it is very heavily used for other recreation including beachcombing year-round and swimming or wading during the summer. The beach is littered with the steel fittings and iron spikes and nails from surplus ships run aground and burned following the Alaska gold rush. Searching for these provides recreation.

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Updated: 11/02/98