How to go with the tide

Canadian coastal tides

It’s WWF Water Wednesday, when Love Nature television explores the unique characteristics, natural history, environmental challenges and threats facing waters and aquatic species in Canada and around the world, hosted by WWF-Canada president and CEO David Miller. Tonight at 9 p.m. ET/PT watch Two Oceans, and read on about intertidal zones.

We sometimes talk about “the water’s edge,” but when it comes to the ocean, there’s no permanent line where land and water meet. Instead, the sea moves in and out, usually twice a day, as it’s pulled by the moon and sun. The space that is continuously covered and uncovered by the tide is known as the intertidal zone, and is home to a rich ecosystem that helps sustain life in the water and on land. It’s just one reason WWF-Canada is committed to protecting our oceans and their shorelines. Here are five facts about these ever-changing habitats and the life they support:

1. These zones are brimming with life

When tides are low the exposed shoreline might appear desolate, but these areas are filled with a diverse collection of plants and animals. The amount of wave exposure, competition and the type of shoreline determines exactly what species can live in an intertidal zone. Rocky shores, which tend to be a little steeper, are home to rockweed, barnacles, snails, mussels, sea stars, anemones, chitons, multiple crab and seaweed species. On wide, shallower shores, like those made up of sand, mud and small pebbles, you’ll find everything from clams and sand dollars to mud shrimp and worms.

2. But they’re not an easy place to live

Because its environment is always fluctuating, especially closer to shore, the intertidal zone can be a difficult place to live. At high tide creatures are living in saltwater. At low tide, they could be living in freshwater from rain or runoff, or completely dried out from the sun. Depending on the season, they might also have to contend with huge temperature fluctuations, waves and even ice. But many creatures have adapted to withstand these harsh conditions. To avoid drying out in low tide, species like crabs and snails will hide out under rocks or in moist crevices, while barnacles and mussels will close up tightly, holding small amounts of seawater in their shells.

3. Their inhabitants form very distinct communities

Plant and animal species living in the intertidal zone aren’t evenly dispersed throughout. Competition and predation play key roles in zone formation. To avoid competing with one another for resources like food, light and space, only the species that have evolved to cope with living out of the water live near the shore. Those that dry out easily or are more sensitive to environmental changes, like temperature, live closer to the sea. In doing so, species form distinct horizontal bands along the shore that are relatively easy to spot. Just below the trees you’ll notice a black-grey band of algae and lichens, underneath that there’s often a grey-coloured band of barnacles, followed by a yellow-brown band of rockweed and mussels.

4. They provide an important food source

Countless species are uncovered every time the tide goes out, and because it’s the only opportunity birds and species like bears, wolves or raccoons have to forage this area, the tide’s ebb and flow play a strong role in their lives. The intertidal zone’s abundance of species is also an equally important food source for humans. Along the coasts of Canada, for example, we harvest a variety of marine life from the intertidal zone, including oysters.

5. There are simple ways to reduce your impact on intertidal zones

Our coastlines are beautiful, vibrant spaces. But when hundreds of thousands of people pitch tents on, launch boats from or walk through these areas each year, it can have a negative impact. The plants and animals living on rocks might appear dormant, but they’re very much alive and awaiting the ocean’s return. To enjoy these regions without harming aquatic life, always look before you step, avoid turning over rocks and don’t take anything with you. You can also take part in the Great Canadian Shoreline Cleanup, Canada’s largest conservation-based cleanup, organized by the Vancouver Aquarium and WWF-Canada and presented by Loblaw Companies Limited. In 2015, more than 59,000 volunteers cleaned up more than 2,000 shoreline sites in every province and territory, preventing 175,932 kg of garbage from getting into our aquatic ecosystems, where it degrades habitat and threatens wildlife.

By Jenna Wootton

Tune in every Wednesday at 8 p.m. ET/PT for WWF Water Wednesdays on Love Nature to learn more about current water issues from around the world.