Intertidal Living
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Intertidal Living
on Race Rocks

westside island
The intertidal zone on the West side of Great Race Rocks as viewed and photographed on June 12, 1999 at a minus 0.1 tide. The predominant macroalgae is Hedophylum sp. although immature bull kelp (Nereocystis luetkeana) is also anchored in this zone close to the shore The small island on the North West corner is completely exposed at low tide but submerged at high tide. It contains a rich assortment of hydroids as well as other invertebrates where Dr. Anita Brinckmann-Voss has collected specimens at the zero tidal level.
hydro low
antho plus hydroids
Small pink dots of a Melobesia mediocris, a calcareous pink encrusting algae which grows as an epiphyte on the leaves of surf grass Just below the green fringe of surf grass, Phyllospadix scouleri, pink hydrocorals and other hydroids such as this Abietinaria amphora survive the current and wave swept zone. The hydroid Aglaophemia latirostris with an Intertidal Anemone.
red urchin
Other Cnidarians such as the green anemone, Anthopleura xanthogrammica, are found in the low intertidal area. These large anemone with symbiotic algae are also found in the surge channel on the south-west corner. The knife placed in the picture for scale measures 10cm in length. Giant red urchins Strongylocentrotus franciscanis live here at the upper limits of their range and the purple urchin, Strongylocentrotus purpuratus also inhabits a narrow band in this area. A giant barnacle, Balanus nubilus plays host to a colony of Symplectoscyphus turgidus ( formerly Sertularella turgida) . Hydrocoral, (Allopora sp. ) encrusts much of the substrate
SW cave
sw cave
purp urchin
Two of the small caves at this level yield a variety of invertebrates. The ceilings of these caves usually support a variety of hydroids The floor of this cave on the south-west corner is covered with the red encrusting sponge, Ophlitaspongia Here on the small island, the purple urchins reside in a crevasse next to the mussle Mytilus californianus.
Lester B. Pearson College