How Does an Oyster Filter Water?

An adult oyster can filter up to 5 liters or 1.3 gallons of water an hour. That’s equal to 30 gallons per day, for just one oyster!  Historically, oysters could filter the Chesapeake Bay’s entire water volume in less than a week.  Today, with 1% of the oyster population left in the Chesapeake Bay, it would take oysters nearly a year.


So how do oysters do it?

Oysters are filter feeders, meaning they eat by pumping large volumes of water through their body.  Water is pumped through the oyster’s gills by the beating of cilia.  Plankton, algae and other particles become trapped in the mucus of the gills.  From there these particles are transported to the oyster’s mouth and esophagus to be eaten, then to the stomach to be digested.

Once the oyster removes all nutrients, indigestible material is expelled as feces through the anus.  This waste trails away from the oyster in a string, waving in the current of water that is flowing out of the oyster. Eventually the string breaks off and settles to the bottom, followed by more strings.

The oyster also produces an interesting waste called pseudofeces. Pseudofeces is unwanted material, like silt, that the oyster chooses not to eat, that gathers next to the gills and is expelled from the oyster’s shell via a rapid closing of the valves.

The expelled particles swirl through the water and resemble a puff of smoke. These puffs of smoke are an indication that oysters are filtering the water and doing what they are meant to do.

How Can I Teach About Oysters?

Now that you know a little bit about oysters and how they filter water, share the knowledge with your students! Here are some resources and lesson plans to help you do so:

Please refer to Bay Backpack’s searchable teacher resources section for more oyster-related lesson plans


Sonia Gibson says:

Sonia Gibson…

I appreciate you sharing this article post.Much thanks again. Really Cool….

Blanca Steib says:

Blanca Steib…

I value the blog post.Really looking forward to read more. Really Great….

Azizbek says:

It’s very generous of you and I do appreciate this information.

Guest says:

Thank you so much for this! :D Surprisingly, there aren’t too many things on the Internet about the actual anatomy of the oyster and how their filtering works. I must not be looking hard enough, haha.

michael smith says:

this is awesome it helped me with my classwork. thx