Weekly Sea Discovery: Sea Cucumbers Are Amazing Nutrient Cyclers

While kayaking during our eelgrass surveys this week, I looked down and noticed some bright orange specks hidden amongst the algae and kelp. As we went shallower, I could see that these vibrant blobs were orange sea cucumbers! While nuzzled in between rocks and kelp, these sea cucumbers had their tentacles extended out into the flowing water. Orange sea cucumbers use their tentacles to suspension-feed, collecting small organisms and detritus (decaying organic material) that passes by. 

An orange sea cucumber (Cucumaria miniata) feeding. Photo. Ed Bierman

Check out the video below to see an orange sea cucumber feeding by using its mouth to scrape off the food on its tentacles, by the Marine Detective. 

Not all sea cucumbers feed this way. Another species of sea cucumber local to Mayne Island is the giant red sea cucumber or the California sea cucumber. These sea cucumbers feed differently. Instead of having their tentacles up in the water, they are down on the seafloor, sifting through the sand and rock for algae and detritus (deposit-feeding).  

A giant red sea cucumber feels around with its tentacles along the bottom in search of food. Video by Em Lim, a Master’s student at SFU studying sea cucumbers in Bamfield, BC.

These squishy invertebrates have various important roles in the ecosystems, including filtering sediments and recycling nutrients. Organic material that would otherwise be buried and stuck in the seafloor sediments is eaten by sea cucumbers and made available for other species in their poop! In nutrient-poor zones, this process can ensure other bottom-dwelling species get enough nutrients.

Two giant red sea cucumbers (Parastichopus californicus). Photo: Ed Bierman

In the tropics, scientists have found that sea cucumbers play a part in reducing ocean acidification. Researchers at Simon Fraser University are looking at whether our local sea cucumbers do the same thing. If so, sea cucumbers may be playing a vital role in buffering increases in ocean acidity in British Columbia’s waters. 


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