Diversity of Canada’s Marine Coastal Habitats

Marine habitatshabitats are habitats found along the coasts of the world’s continents.

Did you know?

Worldwide, there are more than 350 000 kilometres of coastline. More than half of that (202 080 km) is Canadian!

Coastal marine habitats are some of the most dynamic habitats on Earth. They are constantly changing because of waves, tides, and surface runoffsurface runoff from land. Because of their close connection to land, they are also very sensitive habitats that can be easily impacted by humans.

There are many different types of coastal marine habitats in the world. In this backgrounder, we will look at the most common types worldwide. We will look at where they are found, what plants and animals live in them, and how they are impacted by climate change.

Intertidal Zones

Let’s start with the hardest to classify because it is as much an aquaticaquatic as it is a living on land habitat. Intertidal zonesIntertidal zones are habitats that are below the surface of the ocean at high tide and above the surface of the ocean at low tide. Because of this, the animals that live there are amphibiousamphibious. This means that they can live on land and in water. In rocky intertidal zones, tide poolstide pools can also form. These provide temporary pools for marine animals such as sea stars, anemones and urchins.

Temperature changes in the ocean as a whole takes time. But in the intertidal zones, temperatures can change fairly quickly. This is why being able to adapt to various temperatures is important for animals living in the intertidal zone. This is especially important in warm, tropical climates. Scientists have found that intertidal snails can completely shut down when the water they live in gets too hot.

Common intertidal animals include crabs, limpets, chitons and barnacles. All these animals have exoskeletonsexoskeletons . These external shells help them from drying out during low tide. Crabs, like other crustaceans living in intertidal areas, can move. This allows them to find food, escape predators and avoid crashing waves.

Limpets 

Limpets may not seem like they move, but they can. Only very slowly! Like other gastropodsgastropods, limpets grazegraze  on algae that grows on rocks and other surfaces. Like snails, they suction themselves to surfaces using a very strong muscular “foot”.

Barnacles

Barnacles are sessilesessile animals. This means that they don’t go anywhere. First they attach themselves to a surface, such as a rock or a pier. Then they stay put for the rest of their lives! Barnacles “close off” at low tide and open up at high tide.

You may have seen photos of lumps on whales. These were likely barnacles! It is thought that whales breach to get rid of these unwanted hitchhikers. Scientists are even looking at how a barnacle’s super sticky adhesiveadhesive could be used for human surgeries! 

Chitons

There are more than 900 species of chitons found throughout the world. All live in the intertidal zone. Chitons have a segmented shell and a foot like a snail. Unlike limpets and snails, some chitons are herbivoresherbivores and some are carnivorescarnivores.

Sandy Beaches

Mudflats are another type of intertidal zone. They look similar to sandy beaches but differ in having muddy, nutrientnutrient-rich soil. This makes them an ideal place for many species.

Finally, intertidal habitats often welcome some more adventurous typically marine or terrestrial animals too, such as this octopus hunting in a tidal pool!

Now, let’s dive into the fully aquatic habitats.

Rocky and Sandy Underwater Habitats

Underwater shallow coastal habitats are very much like the intertidal zone. The animals here still need to be able to withstand waves and tides. However, they don’t need to be able to survive dry periods. In underwater sandy areas, you’ll find a variety of burrowing animals. You will also find their predators, such as sea stars. Rocky areas offer a great variety of hiding spots. This is ideal for young fish and sessile animals that need to hide from their predators.

Estuaries

An estuaryestuary is a place where freshwater meets saltwater. There is a gradient of salinitysalinity as you go from one type of water to the other. Both freshwater and marine species can be found there.

In Canadian estuaries, there is a strong seasonal variation in the types of animals that can be seen. This is especially true in the spring. This is when there is a lot of freshwater flowing into the ocean from melted snow and ice.

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Shown is an aerial view of an estuary. A river is emptying into a larger body of water. The river channel can be seen in the distance. Green islands and thin peninsulas are shown where the river meets the larger body of water. The water is light blue. Tan sediment is visible in the water in several locations, especially close to the land.

 

For the species that can tolerate the variations in salt, estuaries offer plenty of food. It is considered the most productive aquatic habitat. This is because of the high levels of nutrients coming from surface runoff. Surface runoff also makes those habitats prone to pollution from land.

Many marine species also take advantage of this habitat as a nurserynursery. Young fish and other animals often have a hard time surviving in the open ocean. Estuaries provide a safer place to develop into adulthood.

Estuaries are classified according to how they are formed and how the waters mix. For example, a fjord is a type of estuary formed by glaciersglaciers. In a fjord, the freshwater tends to mostly float on top of the saltwater, which has a greater density. In some fjords, glacial erosion results in majestic canyons leading to the ocean.

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Shown is a view from a tour boat at the fjords of the Western brook pond in Gros Morne National Park, Newfoundland and Labrador. A large body of water is surrounded by tall cliffs on both sides. The cliffs are primarily made of tan rock with some green trees and vegetation. The sky is blue with wisps of purple clouds.

 

Salt Marshes

Natural salt marshes another type of intertidal habitat.

Salt marshes can be found between land and estuaries, or between land and bodies of saltwater.

At high tide, the habitat is flooded. At low tide, the habitat is drained of its water.

Salt marshes are found throughout the world, except in places where ice doesn't allow plants to thrive.

Image - Text Version

Shown is an animation of a salt marsh as the tide comes in from two different perspectives. Both show how the rising tide impacts various zones of a salt marsh. As the water rises, it first fills the pools and mudflats which have a brown, textured appearance. It then rises up to the low marsh which is made up of marsh flats which are vegetation on top of a layer of peat. The water finally reaches the high marsh. It stops right before flooding the trees that are located at the upland zone on a levee.

To live in salt marsh, plants must be able to tolerate high levels of salt. Plants that are able to do this are known as halophyteshalophytes. The word “halophyte” comes from the ancient Greek words Halo meaning “salt” and phyto meaning “plants”. Most normal plants would die in those conditions, but halophytes have some special adaptations. Some halophytes have found ways to prevent the absorption of salts through their roots. Others can excreteexcrete salt through their leaves. Others have special salt glands to excrete salt.

Halophytes are essential for stabilizing the land and protecting it from erosionerosion. Salt marshes also protect the land by reducing the impact of storms. Salt marshes can slow down waves before they reach land. This ability of marshes to do this has been studied a lot in recent years, especially due to climate changeclimate change. Realizing their importance, some countries are even building artificial salt marshes to reduce the impacts of rising sea levels.

Image -Text Version

Shown is a colour photograph of an aerial view of a salt marsh. The foreground of the image is made up of large patches of yellow/green grasses surrounded by dark water that is reflecting the blue of the sky. In the background, a small hill rises above the salt marsh. The hill is covered in grasses and dark green trees. A thin beach of tan sand sits between the hill and the marsh.

 

Salt marshes also act as biological filters. This prevents somecontaminantscontaminants from reaching the ocean. For example, they can prevent coastal eutrophication caused by nitrogen in surface runoff. Like freshwater marshes, the ecological valueecological value of salt marshes had long been misunderstood. But now scientists better understand their role, which has allowed many areas to now be protected.

Seagrass Meadows

Seagrass meadows are the equivalent of prairie grasslands, only underwater! This kind of habitat can be found all over the world, including the Canadian Atlantic and Pacific 
coastlines.

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Shown is a colour photograph of a seagrass meadow. The lower part of the image looks like a grassy field, but the upper part of the image is clearly pale blue water. Streams of sunlight highlight and shade the grasses.

 

Did you know?

Marine grass, such as eelgrass, can grow up to 2 metres long.

As with most coastal habitats, seagrass meadows are the nurseries for many species. For this reason, protecting these habitats in Canadian waters also means helping fisheriesfisheries. For example, young codcod are known to live in this habitat.

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Shown is a colour photograph of a seagrass meadow. The lower part of the image looks like a grassy field, but the upper part of the image is clearly pale blue water. A large school of silver and black striped fish swim towards the left.

 

When the Atlantic cod populations collapsed in 1993, more than 35 000 workers lost their jobs and way of life in the Canadian maritimes.This dramatic decline pushed more scientists to research the effect of fisheries on marine ecosystems. As a result, people came to better understand the life cycle of fish and their needs. For cod, this included protecting the seagrass meadows. This also involved reviewing other fishing methods, such as bottom trawlingbottom trawling, that can destroy seagrass meadows. 

Kelp forests

KelpKelp is a group of algae that grow best in cold and nutrient-rich waters. In ideal conditions, it can grow up to 18 inches per day! This creates a perfect habitat to house all sorts of fish. It is also an ideal hunting ground for many marine mammals.

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Shown is a colour photograph of giant kelp in the ocean. A long green stalk stretches up through teal water. The stalk is covered with long leaves pointing towards the right, like flags blowing in the wind. More stalks of kelp are visible in the background.

 

Kelp is also a favorite food for many grazersgrazers  such as sea urchins. In a balanced ecosystem, animals like sea otters and seals control the sea urchin population by eating them. However, in some areas, like the Northwest coast of British Columbia, kelp forests have been destroyed by large sea urchin populations.

The reason scientists found to explain what happened illustrates how complex ecosystems are. Decades ago, when whalingwhaling was legal, whale populations declined. This forced orcas to find other prey, such as seals, sea lions, and even sea otters. As a result, sea urchins had fewer predators, which allowed them to eat and reproduce as much as they wanted!

Image -Text Version

Shown is a colour photograph of a sea urchin on a kelp plant. The water is teal in this underwater scene. The narrow leaves of yellow brown kelp stretch across the top, center, and right side of this image. A sea urchin is stuck to the kelp in the middle of the image. It is circular and dark brown with many light coloured spikes on it. The bottom and left side of the image is made up of grey rock with a variety of colorful algae stuck to it.

 

Sea urchins are not the only animals that eat kelp. Humans also harvest kelp for commercial uses. This includes putting kelp into food for animals and extracting algin from kelp to use in foods and cosmetics.

People are now beginning to realize how important kelp forests are for reducingclimate changeclimate change impacts. This is because kelp forests are great carbon sinks.This means that they capture more carbon matter than they create. However, this is not only true for kelp forests. Seagrass meadows and salt marshes are also important carbon sinks.

Did you know?

Blue carbonBlue carbon is the term used for the carbon captured by the world's ocean and coastal ecosystems.

Coastal Habitat Conservation

This backgrounder was really just a quick introduction into the amazing plants and animals that live in coastal marine habitats. But there are many more living things we didn’t even touch upon. For example, we didn't even mention all of the shorebirds that rely on oceanic resources.

We encourage you to learn more about the habitats close to your community - both terrestrial and aquatic. If you live near a coast, there are ways you can help. You can be a citizen scientist and report species sightings, such as the capelin of the maritimes. Or you can participate in a shore cleanup.

Coastal habitats are home to a huge number of living things, but human activities put increasing pressures on these sensitive habitats. If we don’t protect them, one day, they will be gone!