What are rocky shorelines?

rocky shorelines 1  220x136 hhRocky shorelines are composed of solid bedrock with very little sediment. They are often exposed to tremendous forces from waves and currents. Due to their bedrock composition, they are not prone to erosion in human time scales. Rather, change on rocky shorelines occurs in geologic time, over thousands or millions of years. Rocky shorelines provide habitat to many marine organisms that have adapted to life in this environment.

Where are rocky shorelines found in the CRD harbours?

Rocky shorelines are found in many areas in Esquimalt Harbour and in small areas of Victoria Harbour, such as West Bay, McLoughlin Point, Saxe Point and Harrison Island. Other well-known rocky shorelines in the Victoria area include Cattle Point, Clover Point and Ten Mile Point.

How are rocky shorelines formed/shaped?

The bedrock composing rocky shorelines was formed millions of years ago by geologic processes (see Geological History of Vancouver Island). Glaciers played a large role in sculpting this rock to its present form. They formed fjords and U-shaped valleys, scoured away sediment from some locations and deposited it in others. Evidence of the most recent glaciation (~29,000 to 10,000 years ago) can be seen in the features of much of the exposed bedrock around Victoria. Look for striations (parallel ridges up to a few cm in height), grooves and rounded forms. Most ridges and grooves around Victoria are oriented northwest-to-southeast, in line with the direction the glaciers flowed.

What lives on rocky shorelines?

The plants and animals that live on rocky shorelines have adapted to very challenging conditions. A basic requirement is the ability to hang on tightly, against the constant forces of waves and currents. For example, seaweeds such as kelp hold on with root-like holdfasts, barnacles secrete “cement” and mussels anchor themselves with sticky threads. As in other intertidal areas, marine life on rocky shorelines must be able to survive large temperature and salinity fluctuations as well as dry conditions during the low tide. Some shelled animals can capture a small amount of water and seal it in their shells (e.g. oysters, mussels, barnacles), and mobile animals like snails and like limpets usually move to shady rock crevices as the tide ebbs.

r-sTidepools are unique features of the rocky shoreline. These small pools of trapped seawater can contain creatures that normally occur in the subtidal zone.

Despite the hardships of this environment, abundant nutrients are provided by cool waters and constant flushing. Plant and animal communities become established in the tidal zone to which they are best suited. This results in zones called bio-bands, distinguishable by the type and colour of vegetation and animal life. Some of the organisms that inhabit the various bio-bands of rocky shorelines include:

  • In the backshore zone (above the high tide line): lichens, insects, salt-resistant grasses and other coastal land plants
  • In the upper intertidal zone: lichens, barnacles, periwinkle snails, limpets
  • In the mid intertidal zone: chitons, mussels, whelks, rockweed, sea lettuce, purple laver (a red alga)
  • In the lower intertidal zone: sea stars, sea anemones, mussels, oysters, sea lettuce, red algae, Turkish towel (a red alga) surf grass, hermit crabs, shore crabsrocky
  • In the subtidal zone (below low tide line):, kelp, surf grass, red algae, nudibranchs, sea urchins, anemones, crabs, sponges, sea cucumbers, Greenling (fish), sculpins, rockfish

Why are rocky shorelines important?

Habitat for Plants and Animals

Rocky shorelines are particularly rich in species diversity. The crevices, tidepools, surge channels, ledges and other formations typical of rocky shores create a wide variety of microhabitats for marine life.

Protection from Storm Waves

Rocky shorelines form headlands that shelter leeward shores and provide a natural breakwater.

Education, Tourism and Recreation

With so many species crowded in to a fairly accessible environment, rocky shorelines provide ideal sites for marine biology education. The beauty of these ecosystems attracts visitors and local residents alike to the region’s rocky shores.

What threatens rocky shorelines?

Rocky shorelines are not very prone to erosion, so they are not as vulnerable to disturbance from upland development as shorelines formed of soft sediment. However, the marine species on rocky shores are easily damaged by trampling, harvesting or pollution. Some types of seaweeds are sensitive to shading from structures such as docks, wharves and walkways.

How can I help protect rocky shorelines?

For information on protecting shorelines please visit our How Can I Help section.

Additional Information & Links

© Second and third image courtesy of Stewardship Centre for BC

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