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Amazing Aquarium: The Intertidal Zone at Discovery Islands

“Between ocean and land exists a remarkable place unlike any other in the world—the intertidal zone, where marine ecosystems are both exposed to air at low tide, and under water during high tide. This unique space where land and sea meet is comprised of diverse oceanic systems and a wide array of saltwater species.”

From: The Nature Conservancy of Canada, Land Lines Blog, December 2015

My husband Eric and I circumnavigated Read Island in June 2022, and extremely low tides during the paddling on this trip revealed the extraordinary life in the lowest region of the intertidal zone. Along the coast of Read Island and Penn Islands, strange creatures we had never witnessed before were on full display above the water on the rocky shores. The most amazing natural aquarium was witnessed from our kayaks!

The three-night Read Island circumnavigation launched at Hoskyn Landing on Quadra Island, with a planned clockwise route around Read Island. Our three planned campsites were South Rendezvous Island south, Penn Islands north, and Read Point east (which we were unable to find, so we continued on to Freedom Point instead).  

We sourced all our campsites using the BC Marine Trails map tool. Study resources used for this article are listed at the end of the article.

Eagles’ Nest at Frederic Point, Read Island

An especially memorable and favourite section of the trip was the intertidal aquarium we enjoyed after leaving the Penn Islands, travelling south along Read Island to the next campsite.

We crossed Whale Passage to Frederic Point on Read Island, where we were treated to the spectacle of a couple of active eagles in a nest high up on the point.  We looked at the campsite on this point, which is listed on the BCMT map, completed a circuit of Evans Bay (Read Island), and stopped for lunch.

Low tide was shortly after our lunch break, reaching a remarkable low of 0.8 meters (2.6 feet)—about four meters below the high tide level. This is when the day became truly special. With such a low tide, we were treated to the surprising creatures and sights in the lowest depths of the intertidal zone.

As we hugged the shoreline heading south along Read Island, the strangest sights began to emerge along the rock ledges of the shore. About four meters of rock face that would be underwater at high tide, was exposed above water. It was a visit to the lower intertidal zone from the seat of my kayak!

Two giant red Sea Cucumbers, a Limpet (top center), and Sea Urchins (bottom right) at very low tide

What are these strange, spiky, orange sausage things? We researched a few of the creatures when we returned home and learned these are “giant red” or California Sea Cucumbers. The sea cucumbers remove excess organic stuff from surrounding water—they filter or absorb the uneaten feed and waste from fish farms. Perhaps with the recent closure of fish farms in Discovery Islands we’re seeing more sea cucumbers spreading around the region? (Just my own speculation!)

Sea Star (purple), Sea Anemones (“hanging globs”), and a Chiton (to the left of the sea star)

What are these peculiar globs hanging from the rocks? The sea anemones, attached to rocks high above the water, were truly interesting! Below the water, sea anemones are nice and plump, partly open, and are exposing the tentacles used to catch prey. Anemones out of water have their tentacles retracted into their bodies to prevent drying, and appear as sagging, wet, squishy lumps. We saw multiple types of anemones. Did you know that some sea anemones can clone themselves?

Clusters of Sea Stars (purple), various Sea Anemone, and a single ochre-coloured Sea Star above the Water at low tide

Ochre Sea Stars were fairly abundant on the rocky shores, in mostly purple and some ochre colours. There are indications that the population of these marine creatures is recovering after the decade-long sea star wasting syndrome, which decimated their numbers. Did you know the ochre sea star is a keystone species? They keep the populations of mussels, barnacles, and sea urchins in check as these are favourite foods. So, please don’t touch these creatures if you are lucky enough to see them—help protect and preserve this special species by taking photographs only.

Ochre Sea Star Cluster (purple), and Plumose Anemone (below the water) at low tide

Leather Stars are a type of sea star, and a few of these appeared too in our tour of the intertidal aquarium. Leather Stars often feed on anemones, but will also consume sea cucumbers, sea urchins, and chitons.

Did I mention we even saw chitons? Chitons are molluscs with eight plates that act as armour on their backs. These plates are mobile, and allow the oval-shaped mollusc to curl itself into a ball when hiding from predators.

Sunflower Sea Stars, with 16 to 24 limbs, are very uncommon, so we did not see any on this trip. However, I was lucky enough to see a Sunflower Sea Star on another trip to the Discovery Islands at low tide. If you’re lucky you will see one in this area!

In the Discovery Islands you will see lots of Pacific Purple Sea Urchins, ranging in size from very small to very large, and these creatures devour the kelp forests, unfortunately. Sea urchins are a favourite food for sea stars, so it’s great to see a revival of sea stars that will keep the sea urchin population in check, helping to save kelp forests. Another way to help save kelp forests is for humans to eat more sea urchins! Hmm, Uni, a sushi delicacy! Sea Otters also love to eat urchins, however, you will not likely find any Sea Otters in the Discovery Islands today.

Exposed Rocks several meters below the high tide level

Exploring the intertidal zone from your kayak is an educational experience. I am not at all a marine biologist, yet found it very interesting to research some of the creatures when I returned home—to learn about what they are, how they fit in the ocean ecosystem, and their behaviours, life cycle, habitats, reproduction, and history.

I can highly recommend this experience! Check your tide table to find the ideal time to go and explore our natural aquarium in British Columbia!


Feature photo: Lycette Clark, “Ochre Sea Star (purple), Sea Anemones (“hanging globs”) and Leather Star on right at very low Tide”

Intertidal Zone quote: The Nature Conservancy of Canada: Land Lines Blog, December 4, 2015

Sea Cucumbers: Infotel: Is the lowly sea cucumber the new superhero of sustainable aquaculture?

Sea Anemones: Introduction to Sea Anemones: E-Fauna BC, Electronic Atlas of the Wildlife of British Columbia

Sea Stars: UC Santa Cruz: MARINe Multi-Agency Rocky Intertidal Network

Leather Stars: Vic High Marine: Echinoderms

Chitons: Mayne Island Conservancy: Chitons

Pacific Purple Sea Urchins: Oceana: Marine Life Encyclopedia

Lycette Clark

Lycette and her husband Eric discovered a keen adventurous spirit for exploring remote British Columbia coastlines after starting multi-day kayak tripping in 2020. Based in Victoria, British Columbia, Lycette is a volunteer for the BC Marine Trails Stewardship committee and a Coastal Caretaker.