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What’s That Smell?
Have you ever walked by the beach during low tide and thought Ew! What is that smell? Well, a few days ago when I was participating in a beach clean up along Crab Cove, my brother had exclaimed the same thing as we stepped onto the beach to look for trash.
If you have been on a beach during low tide, you might have thought you smelt something like rotten eggs, old seaweed, or even wet dog fur. If the answer is yes, you’re not alone! Lots of people notice a stinky, salty, seaweed-y smell when the tide goes out. But guess what? That smell is actually a sign of life—and it’s part of the amazing story happening right below the waves!
What Is Low Tide, Anyway?
What Is Low Tide, Anyway?
Our Earth's ocean is always moving. Sometimes it rises up and covers the beach, and sometimes it pulls back and leaves behind wet sand and mud. This rise and fall is called the tides, and it’s controlled by the gravity (gra-vit-ee) of the moon and sun. It is considered most predictable phenomena of our world. Weather forcasts and local websites can even tell you the time of each tide! Tides start from the ocean and move into the coastlines we see by our beaches.
There are two main tides every day:
High tide: This happens when the water is at its highest and comes in and covers the shore.
Low tide: This happens when the water pulls away and more beach or mud is showing, which allows us to see more creatures, animals, birds, and cool rocks!
When you can see parts of the Bay that are usually underwater become visible, that's a sign it's probably low tide. We can see things including mudflats, where lots of animals live, dig, and hide and that’s when the funky smell comes from!
So… What’s That Smell??
So… What’s That Smell??
The muddy shoreline is full of powerful natural processes at work, especially when it comes to breaking things down and recycling nutrients back into the ecosystem.
Decomposing plants and animals! When seaweed, algae, or tiny dead organisms get trapped in the mud, they begin to break down. This might not sound very exciting, but it’s actually an essential part of the ocean’s recycling system, helping to return nutrients to the environment so new life can grow.
Another important part of this process comes from bacteria! Special bacteria living in the mud help break down organic waste, including dead phytoplankton (fi-tow-plang-k-ton). These microscopic, plant-like organisms are a major foundation of ocean life. As the bacteria do their work, they release gases such as hydrogen sulfide, the same gas that gives off a strong “rotten egg” smell you might notice at the beach.
Environmental conditions like warm weather can make these smells even stronger. On sunny days, when the tide is low and the mud is exposed, the surface can heat up quickly. This warmth speeds up decomposition and causes more of those gases to be released into the air.
So that “yucky” smell you notice along the shore? It might not be pleasant, but it’s actually a sign that nature is hard at work. It’s all part of a healthy, functioning ecosystem doing its cleanup job and keeping the cycle of life going.
The Mudflats Are ALIVE!
The Mudflats Are ALIVE!
At first glance, they might look like nothing more than a wide stretch of squishy mud. But if you pause, crouch down, and take a closer look, perhaps even with a magnifying glass, you’ll discover something amazing. Beneath the surface lies a bustling, hidden city filled with all kinds of creatures going about their daily lives. What seems quiet and still is actually full of movement, activity, and surprising diversity.
During low tide, this secret world becomes easier to explore. Tiny but hardworking ghost shrimp are among the most active residents, constantly digging and maintaining tunnels deep in the mud. You can often spot their presence by the small, volcano-shaped mounds they leave behind. Nearby, shore crabs scurry about, quick and alert. These little climbers and diggers can sometimes be found by gently turning over rocks or watching closely along the muddy edges of the shore.
If you look carefully, you might also notice signs of clams and worms hidden beneath the surface. These creatures play an important role as filter feeders, helping to keep the water clean. Small squirts of water shooting up from the mud or shallow, coin-sized dips in the sand are clues that they’re just below your feet. Along the shoreline, you may come across eelgrass beds, which appear as thick mats of green and brown during low tide. When the tide rises, these same patches transform into underwater meadows that provide shelter and nursery habitats for young fish and crabs.
Above it all, shorebirds bring even more life to the scene. Birds such as godwits, curlews, sandpipers, and egrets can often be seen walking along the water’s edge. Using their long beaks, they probe the mud between the waves, searching for tasty snacks hidden below. Together, all of these creatures make the mudflats a vibrant, living ecosystem: one that rewards anyone willing to slow down and take a closer look.
These creatures and the environment around them depend on low tide to feed, rest, and breathe. Even though the Bay might look calm, there's a ton of action going on just under the surface which we can see when the low tide comes! So next time you wrinkle your nose at the smell that comes with low tide, remember—the smell means the Bay is alive, doing its messy, muddy work to support the whole ocean!
Fun Fact! Lowtide is considered the most efficient time to conduct beach clean ups. Since the water is pulled back, trash and debris from previous storms or other bodies of water can stay on shore longer, making garbage easier to collect. Self-guided cleanups can be totaled with other community efforts if you log into the data collection app---Cleanswell! Check out this California Coastal Commission website for more information: https://www.coastal.ca.gov/publiced/neighborhoodcleanups.html
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