What Do Clams Eat? The 5 Foods They Consume

Written by Kyle Glatz
Published: December 15, 2021
Image Credit Greg Amptman/Shutterstock.com
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Clams are bivalve mollusks that generally thrive in freshwater and saltwater settings. Although they resemble other mollusks like oysters and mussels, clams have some unique characteristics that make them worth examining. For example, their means of locomotion, a “foot”, along with their feeding methods are just two interesting facets of clams. Looking at these creatures, it can be hard to imagine that they eat at all, so let’s answer the question, what do clams eat?

Discover what foods they prefer, how they process a meal, and what creatures are trying to eat them, too!

What Foods Do Clams Eat?

What Do Clams Eat
Clams eat plankton, algae, and other organic matter.

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Clams eat algae, zooplankton, phytoplankton, and other organic matter that passes through their filtration system. These mollusks are omnivores that eat both plants and animals, albeit in their smallest forms. These bivalves do not have a voracious appetite, but they eat all the following:

  • Algae
  • Byproducts from symbiotic algae
  • Zooplankton
  • Phytoplankton
  • Organic matter flowing in their aquatic habitats

Although these broad categories of foods might make it seem like clams do not eat a lot of food, the truth is that the clam’s diet has serious variety in it. As filter feeders, clams will eat anything with nutritional value that comes through their siphons.

That could be organic matter from decaying plant life or even excrement from aquatic creatures. In that sense, the clam’s diet can be very diverse under the umbrella of these five types of food.

How Do Clams Eat Their Food?

Animals That Don't Have a Brain - Clam
Clams filter-feed to obtain food and also form symbiotic relationships.

maya_parf/Shutterstock.com

Clams use very intriguing methods to obtain and consume their foods. For one thing, clams can move a little bit with the help of a “foot.” They use this conical muscle to better position themselves in water to obtain nutrition. They do not bind themselves to a substrate like oysters; they’ll find an area rich with food, and burrow enough to stay put while they feed.  

Clams obtain their food by filtering water through an intake siphon and an exhalation siphon in their bodies. Food passing through their gills is trapped in a sticky mucus that moves through cilial action to the labial palps and later to the clam’s mouth. Plankton, algae, and organic matter are consumed this way.

Clams also have another method for obtaining nutrition, too. Some species of clams develop a symbiotic relationship with algae, such as zooxanthellae. These algae live in the mantle of the clams. While the mollusk takes in and feeds the algae the nitrogen it needs to thrive, the algae provide the clam with various nutrients.

All told, clams can process about 24 gallons of water each day in search of food.  

What Do Clams Eat in Winter?

digging for clams
Clams bury themselves and go dormant in winter, but they can be harvested during this time.

knelson20/Shutterstock.com

The clam’s “foot” helps the creature move around to more habitable areas or find safety by burrowing into the sand. Typically, they will only dig down into the sand or mud enough to keep themselves safe from predators but not too deep that their siphon can’t bring in nutrient-rich water.

During the winter, clams use this muscle to dig an extra-deep hole for themselves. This burrow is slightly deeper than their siphons are long, effectively burying them for the duration of the winter season. The clams go dormant for the season, beginning when the temperature dips below freezing.

In other words, clams eat very little, if anything, during the winter as they are too busy trying to survive the cold that accompanies the season.  

What Impact Does the Clam’s Diet Have on Others?

A massive Giant clam (Tridacna gigas) grows on the seafloor in the Republic of Palau
Large clams help remove excess nutrients from waterways, improving the environment.

Clams’ filter-feeding methods have a significant impact on the bodies of water that they inhabit. Specifically, they can help prevent eutrophication, the process by which excess nutrients in bodies of water leads to suffocating algae blooms, increased phytoplankton levels, and low oxygen levels.

Eutrophication can cause mass fish deaths and create cascading damage to the ecosystem. Fortunately, clams and other mollusks, like oysters, help remove a lot of the excess nutrients through their filter-feeding. The symbiotic relationship between clams and zooxanthellae is even more beneficial in this light, removing nitrogen from the environment while also creating food for itself.

 A large clam can filter up to 24 gallons of water each day, so areas with thousands of clams can remove quite a bit of nitrogen and phosphorous from a body of water throughout the course of a year. That results in cleaner waterways and a thriving ecological system.

All told, the foods consumed by clams have a significant and measurable impact on the environment, and this effect might be purposely utilized in the future to repair waterways.

What Predators Eat Clams?

Largest eels - California moray
Eels can crack a clam’s shell and eat the mollusk within.

Clams are invertebrates with soft bodies wrapped in a hard shell. Unfortunately for them, their shell and the ability to bury themselves in sand and mud are the only means of protection available to them. These creatures are very easy to prey upon, and many animals throughout the world take advantage of the clam’s helplessness.

Even though they have a rudimentary foot protrusion, it is not enough to help them escape predators even when they are buried.

The most common clam predators include:

Each of these creatures can pry open the shell or otherwise get to the clam’s soft body. Human beings are the most dangerous of all to the clams because they frequently catch and eat clams as part of their diet or kill them and keep their shells for decoration.

Clams are somewhat unfortunate in the sense that they lack a way to fight back against predators or detect them in time to close their shells all that often. Their environment does help to a degree, though. Fortunately, most common clams are not endangered.

Clams might not be exciting creatures at first glance, but they have many interesting facets. Their contributions to the environment, symbiotic relationships with algae, and the mere presence of their “foot” make clams worth looking at with a sense of intrigue. The clam’s diet is not particularly exciting, but it is diverse and helps keep their waterways clean.  

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About the Author

I am a freelancer specializing in SEO content writing. I write in a variety of niches such as video games, animals, and managed service providers. I've been writing full-time since 2018, so I've been doing remote work before it was cool. When I'm not working, I can be found reading, trying to catch up on my tv show backlog, playing video games, and starting stories that I'll never finish.

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