A new study found that a species of Sea Snails found on the beaches of Cortes, Quadra and neighbouring Discovery Islands is already experiencing ocean temperatures beyond their comfort zone. According to the associated UBC press release, oysters will survive as the oceans warm up, but the Nucella lamellosa might not. 

“I conducted a research study using a combination of field and lab experimental methods to answer the big question: are marine ecosystems going to be able to keep up with the rate of environmental change that they’re experiencing? We know that species can respond to ocean warming by moving, by genetically adapting, or by acclimatizing within generations. Every species is going to have a different ability to employ those strategies based on its traits,” explained Lead author Dr Fiona Beaty, from the University of British Columbia.

“A snail, which is the species I looked at, can’t move very far quickly. So we’re going to expect that as snails are experiencing ocean warming, they’re going to have to genetically adapt or acclimatize to cope with warming conditions. We know that populations have different abilities to do that.”  

“I specifically chose this species of marine snail, Nucella lamellosa, because I anticipated that it would be vulnerable to ocean warming due to its life history traits. It lays egg capsules and the babies crawl away from the eggs, and it’s a snail.  It’s highly likely that the species’ genetics are quite localized within the Salish Sea. This is one of the warmest parts of that species range. So we can expect that populations here are already among the most warm adapted out of the species.”

“I wanted to see how two populations along BC’s coast are going to respond to future warming. I found that one population looks like it’s going to probably be okay as its seawater warms because the temperatures that it’s experiencing right now are quite far away from the upper maximum temperatures that it can tolerate and grow. Whereas another population in our beautiful Salish Sea is a lot more vulnerable because it’s already experiencing seawater temperatures that are quite stressful, and the seawater here is warming at twice the global average rate of warming, so it’s quite a different picture, even though these two populations are only 400 kilometres apart.” 

Cortes Currents: “Where was your study area?”

Fiona Beaty: “My field sites were just south of Departure Bay. Two sites, one at Cedar Boat Launch and one at Blue Heron Park, south of Nanaimo. And then my other field sites were up on the central coast of BC. My research was in partnership with the Hakai Institute and I worked at their research station on Calvert Island.”  

“I didn’t do any sampling around Cortes or Quadra, but Cortes and Quadra fall in the middle between my sites.  They are at the northern extent of the Salish Sea, so we can anticipate that species that live around those shorelines might very well have similar vulnerability to climate change, although I will note that there is a higher current around the Discovery Islands.”

Beaty directed Cortes Currents to a video depicting the expansion of warmer than normal ocean waters into our area, as well as the rest of the Salish Sea, every summer between 2016 and 2022. (Look under ‘Supporting Information’ at the bottom of the linked page.)

Fiona Beaty: “Even though snails in the Salish Sea can’t just up and go to the central coast very easily, unlike a bird or a fish species,  they can move around in the intertidal, and they do.”

“There have been studies of Nucella ostrina (another Nucella species that lives in slightly more wave exposed shorelines), that put a little tracker on it and watched how they move around in the shoreline.  They found that these snails can predict, or anticipate, the tidal cycles and when they might be exposed to hot air temperatures. They also opportunistically forage during high tides, so they’re not exposed and vulnerable during low tide when the air temperatures are hot. They can move around within the intertidal to try to reduce their exposure to hot air temperatures.  If you’re under a rock in the intertidal at low tide, for example, you’re going to be a lot cooler than if you’re on top of the rock.”

“I was only looking at seawater temperatures, so the duration of time that the snails are immersed underwater.  I found that for the Strait of Georgia, the populations  are already experiencing quite stressful seawater temperatures. Their only option really would be to try to go deeper in the ocean because generally temperatures decline with depth. If they did that, then they would be shifting their exposure to things that they need to eat and they would also be shifting their exposure to things that would eat them.” 

Cortes Currents: One of the things that caught my interest in the UBC press release is the statement, ‘Creatures like oysters, Northern anchovies and whales are more likely to survive in the warming oceans.’ One of Cortes Island’s principal businesses is growing oysters. 

Fiona Beaty: “Oysters have a variety of life history traits that make them potentially more resilient to future warming, depending on what type of oyster species we’re talking about. Within the Salish Sea, we have a non-native oyster species, the Pacific oyster, which is principally used in many aquaculture facilities and it’s beginning to be able to naturally recruit within our water. 10 or 20 years ago, the Pacific oyster couldn’t naturally recruit because it requires warmer temperatures. Now that our seawater is warming up, we’re seeing self-sustaining populations of Pacific oyster beds growing throughout the Salish Sea. That could indicate that in the future, we might expect to see more of our shoreline dominated by oyster beds.  We might even see the replacement of mussel beds with oyster beds”. 

“The reason why I say that is, when we experienced the 2021 heat dome,  there was massive shellfish mortality and invertebrate and animal mortality along the shorelines of the Salish Sea. There was higher mussel mortality than there was oyster mortality. Oysters seem to have slightly higher tolerance to those crazy hot temperatures, whereas the mussels didn’t fare so well. My precious snails really didn’t do well. Nucella lamellosa were among the species that had the highest mortality during that heat dome effect.”

“Pacific oysters come from Asia’s shoreline and they have ended up in our bodies of water due to aquaculture and also due to ballast water transfer of species, from one region to another due to shipping.” 

“We can probably expect that the shorelines in the Salish Sea are going to look a lot more like the shorelines along Hong Kong and in the warmer regions along Asia’s coastline because the temperature gradient along the West Coast of North America isn’t linear.  The Salish Sea is the warmest body of water that species experience until Southern California and Mexico.”

Cortes Currents: Why is the survival of the Nucella lamellosa important? 

Fiona Beaty: “We have to think about the broader ecosystem and all the tiny little species that we don’t even know exist, or we can barely see. These are all incredibly important to building our complex and diverse and beautiful and resilient natural systems that we as humans so deeply depend upon and are related to. For me, the snail  represents one of those species. It doesn’t have a voice. It’s not necessarily a big charismatic one, but it’s very important within the intertidal. It’s  a charismatic predator,  so it drills into muscles and it drills into barnacles to eat them.  It’s a carnivore, as opposed to some other snails that are herbivores and graze on seaweed and whatnot, and  it is prey to Dungeness crab, to seabirds, and other invertebrates.  If we lost the species, it would mean that there’s altered interactions amongst the intertidal community that could lead to quite stark shifts in what we see when we go down to the beaches.”

Top image credit: close up of two Nucella lamellosa or frilled dogwinkles. Credit: Dr Christopher Harley

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