What is this Jelly-like Blob Under My Dock?

This site is supported by donations. If you find the information helpful or interesting, please click here to make a small contribution (credit card or PayPal). Thank you!

The Question: I was swimming in the lake behind our house with a friend one day and we found a thing attached to our dock and it appeared to be brown fish egg sacks. But with closer observation it turns out to be a jelly like substance. What is it?

Submitted by: Kali, Tennessee

(click on photos and graphics to expand)

"Pectinatella magnifica 8568" by Jomegat
Freshwater bryozoan (photo by Jomegat)

The Short Answer: Without any other information or photos, it’s hard to be definitive about this, but usually, when people ask this question, what they have found is colony of the freshwater bryozoan Pectinatella magnifica. Freshwater bryozoans are tiny colonial animals that can form jelly-like masses, which are often found attached to sticks or docks.  Bryozoan colonies can be as much as a foot (30 cm) in diameter.

This Youtube video shows a couple of very nice bryozoans blobs: http://www.youtube.com/watch?v=g1H3e0Iynso

Pectinatella magnifica (photo by Triclops200)
Pectinatella magnifica (photo by Triclops200)
Pectinatella magnifica
Pectinatella magnifica

More Information: Though they are not closely related to corals, bryozoans are superficially similar in that they are tiny colonial aquatic creatures that effectively filter particles from the water. The large gelatinous species is native to North America and often grows on docks and other submerged wood. During the summer it releases small larvae that swim away and establish new colonies nearby. In the fall each colony produces thousands of tiny, seed-like disks that remain dormant over winter and germinate the following spring. Most other freshwater bryozoan species form branching tubules that resemble brown moss in the water (Bryozoa = “moss animal”). While freshwater bryozoans improve water quality, some species become a serious nuisance when they clog intake and irrigation pipes.  For further information on freshwater bryozoans, the site of Dr. Timothy Wood at Wright State is very helpful: http://www.wright.edu/~tim.wood/bryozoans.html. (My thanks to Dr. Wood for his help in preparing this answer.)


This Youtube video shows a very nice view of a bryozoan filtering food particles out of the water: http://www.youtube.com/watch?v=utPtyceR_YY&feature=related

This site is supported by donations. If you find the information helpful or interesting, please click here to make a small contribution (credit card or PayPal). Thank you!

Cite this article as: Pelletier, TC. (September 16, 2010). What is this Jelly-like Blob Under My Dock? Retrieved from http://askanaturalist.com/jelly-like-blob-under-my-dock/ on November 19, 2017.

44 thoughts on “What is this Jelly-like Blob Under My Dock?”

  1. I was cleaning the weeds from around our boat and saw two opaque jelly like substances just below the surface of the water(looked like jelly fish)among the weeds. I caught one on the fork and removed it with the weeds, the other one quite large in size like a small football slipped of the fork and escaped. This was in the Trent canal system in the Bobcageon area. Has anyone else seen anything like this, does anyone know what I saw and has anyone else seen anything like this.

  2. Yes we have recently found some too around our beach as we were cleaning the weeds. i was interested in finding out what it is

  3. Marcus and George,

    Sounds to me like what you’ve found is the bryozoan Pectinatella magnifica. I assume you read my article on these blobs, but if not, you can find it here:

    What is this jelly-like blob under my dock

    The other commonly found blob-like things found in fresh water in North America are amphibian egg masses. But as you both are reporting these in mid-late August, that’s very unlikely. Most amphibians lay eggs in the spring. So I’m pretty sure what you’ve found is a bryozoan colony.

    Here’s another site with good info:

    ALIEN LIFE FORMS? NO, JUST BRYOZOANS

  4. Pingback: Ask a Naturalist.com » Jelly-like blob under the dock – part two
  5. Pingback: In Case You Were Wondering | Brandy Lake Muskoka
  6. I have some photos of very strange gelatinous blobs attached to submerged twigs and branches in the waterways near my home. I kayak a lot and see them everywhere but don’t know what they are. Is there a way for me to upload any of these photos for identification or can I attach them to an email? I’d appreciate the help, I’m very curious. They look almost alien. lol

  7. Pingback: Ask a Naturalist.com » What are these green jelly blobs?
  8. Pingback: Ask a Naturalist.com » Donut blob that stumped the experts …
  9. I have also see “jelly-like blobs” in Stoney Lake. I have been told they may be algea. I have a photo if you tell me how I can post it.

  10. Hello, I am a junior high science teacher and one of my students brought in a jelly like blob he took out of the Maumee River near Waterville, Ohio. The blob itself has algae growing on the outside of it, but is clear on the inside. It doesn’t appear to have any visible structures (individual sacs, cell membranes…) It really just looks like a lump of goo. Any suggestions? Thanks so much

  11. I’ve been seeing these gelatinous blobs for years in one local lake in particular. They are very strange both in appearance and texture. I’ve often thought that they must be some form of aquatic organism since I usually don’t start seeing them until late summer or early fall, and this article now confirms my suspicion. Thank you very much for the information!

  12. I’m so sorry for the delay in responding. Did you by any chance take a photo? Late in the season, the bryozoan colonies drop the statoblasts, which are the darker colored structures that give the colony the speckled or polkadotted look. Once they do that, what’s left is a pretty clear blob. Which can then be colonized by algae and molds. That might be what you have.

  13. I’ve been seeing these for years growing on trees in a local lake that I fish. Curiosity finally got the better of my friend and I. I plucked one off a submerged tree near the surface, and set it on the boat to examine it. My friend also picked it up to take a look at it. About 5 minutes later we both had allergic reactions that looked and felt like Poison Oak going up our arms, the reactions lasted about 30 minutes and then went away. Interesting creatures, just be careful when handling them!

  14. Found dozens of them washed up on shore at Barren River Lake SP in KY after a rain storm on Halloween night. 2 were bigger than a football.

  15. My husband and I saw many of these in Lake Grapevine in Texas. These are very strange. Thanks for the identification of them. Are they appearing in the lakes due to polluted water? Our lake even has aerorator over by our dam. I think they are gross and just wonder if those are growing what else is. And what do we need to do about it.

  16. Leah, I can’t find a lot of information on bryozoans and water quality, but what I did come across suggested that bryozoans are associated with good water quality, not bad. Bryozoans filter algae and other microorganisms out of the water, so they would tend to make the water clearer, and some people have speculated that they can change the ecosystem by doing that. I find that a little hard to believe, unless there were a lot more of them than I’ve usually seen. So I don’t think you need to do anything about them. And their scientific name is Pectinatella magnifica, so you can think of them as “Magnificent Bryozoans.” Does that help change your image of them?

  17. Hello! I picked up a piece of plastic that had been sitting out in the yard for about a year now. Under the plastic were two clumps of white squishy eggs. I felt so guilty that I had uncovered them, so I scooped them up in a handful of dirt and put them in an aquarium buried with moist soil. I want to know what they are and how to keep them alive! Please help me!

  18. Have Bryozoans on my boat lift tanks and hoses.
    Notice my lift comes up after I take the boat out. Would the broyozoans have air inside that could cause the lift to rise?

  19. Hmmm …. interesting question. They don’t usually float at the surface, but that’s because they typically grow around a stick or rope in the water. I actually don’t know if they would be buoyant if they weren’t attached. Anyone?

  20. I was climbing up the ladder on our dock at the Lake of the Ozarks when I felt a familiar creepy feeling. I had felt these gross creatures before. They were Bryozoans. I went up to the house and got rubber gloves and pulled off 2 Bryozoans from the steps of the ladder. They each were about the size of 2 softballs put together but in the shape of a football. After taking pictures of them I threw them back in the lake. When I threw them they were heavy enough that they sank. I looked back out at the lake a few minutes later and they were floating and small fish were eating them.

  21. Those things are gross. Are they harmful? They are showing up all over the pontoons on out boat.

  22. My sighting was on the underside of a boat on our lake in NE Washington state. I lifted the boat to drain water and saw a long very smooth and clear jelly like tube attached to the bottom. Inside the gel was a small amount of dots– seed-size. It was about a foot long and maybe an inch or two wide.
    ???

  23. Tom– I wish I did! I was trying to keep a squeamish daughter from noticing it and didn’t take a pic! I’m going to tomorrow if it’s still around.
    It was loosely attached to the boat underside with the whole length of the “jelly tube.” When I tipped the boat it gracefully detached except for one end where it stayed secured.

  24. We found one of these Magnificent Bryozoans in the Golden Cedar River in Gladwin MI during a river cleanup project in late August 2016. We had a retired doctor with us as a river cleanup volunteer who was knowable of many plant and animal species but not this one. He picked it up and it split in half rather (too) easily. The kid in my canoe, smelled the inside of it and said it smelled like “crap”. It looked amorphous inside with no features except a columnar tube-like structure like you would see if you broke open a coral reef or a bunch of straws piles in a straight line but without the surface texture. Each column seemed to have a hexagonal or circular shape and they went to the center of the ball and met with the ones on the other side of the sphere. The center was not defined with any feature that I could see. We did take some photos but the flash was on and the images are burnt out pretty much. He wrapped it in a towel took it along to examine it more later when he gets home but when he got to the takeout landing, it smelled so bad that he tossed it because he wasn’t in his own car and the driver said he didn’t want it in there. He will be happy to know it really is a living specie. Thanks for this page.

  25. A photo of one of these broken open can be found here:

    http://www.brcleansweep.org/2016_0825_GCR_small/33.html

  26. My science teacher recently found a blob that is monochromatic in grey, no patterns but kind of looks like ones in the pictures above in lake muskoka, and its tiny and apparently theres a zebra mussel on the weed its attached to. Im not sure if its the same one though? Is it?

  27. Found these bryozoans in the Monksville Resevoir, NJ attached to logs as well as concrete walls. Thanks for your explanation. We thought they were proof of aliens. I took pictures. If you want them, let me know.

  28. Trying to find any info on a gelatinous, clear, jelly like organism that lives on land (no bodies of water nearby) and moves. One was rolling (for lack of a better word) through our house. Must have gotten in through the back door when we left it open for a breeze. I can only find info on blobs that thrive in water (bryozoan, salps, etc). Looked more like a salp.

  29. We seem to be finding more and more of these blobs in the canal. Are they an invasive species?

  30. Hi Nanci, it’s hard to answer your question because I don’t know where you live. As far as we know, Pectinatella magniifica is native to North America, and I have not heard or read of any places where it creates a serious problem. However, it has been introduced to Europe and other parts of the world, and they are more worried about it. Even so, I have not seen any evidence that it causes environmental problems. One recent study in the Czech republic looked for toxic-algae toxins, but didn’t find any.

  31. I have found two in the past week. One in Nashua, NH on a river, one in Derry, NH on a lake. Very interesting! What people don’t realize is that they are hard like rubber, although they look soft, like jelly. Mine look exactly like they ones you have pictured.

  32. My husband found one by our dock. He put it on the dock and after about 1/2 hr. it rolled off the dock and quickly floated away. It was strange to see – we’ve never seen these before and now we’ve seen at least 4 of them in the past 2 weeks. I wonder why they would now start to show up??

  33. This is the time of year when people typically start reporting them. They grow bigger over the summer and then die out and start over again every spring, so this is the time of year when they are more noticeable. Are your water conditions different this summer? Warmer? Colder? They filter microorganisms like algae out of the water, so if you’re having more microscopic algae and other organism this year, that might have led to larger growth.

  34. Thanks Tom! Very helpful as we have a lot of these colonies in our brown lake in Western Washington state. I’m glad to hear they clean the water.

  35. I saw someone ask if they are buoyant. I believe they are not. We have them attached to a rope, and the weight of them is actually pulling the rope down in the water!

  36. I found one in river I kayak often in Western Mass. Sent pics to my son. A week later Gizmodo published pic of similar object and what it was. Very interesting. And great to know it’s helpful to the eco system where it is and that it will be back again next year. Will search for it as kayak season gets into swing 2018.

  37. Have just seen several bryozoans this week in the Oxtongue River in Haliburton County, Ontario. The largest was football shaped, 10 inches long, and 4 inches wide. All were attached to reeds in the water and sank when the stems were detached from the bottom of the river.

Leave a Reply

Your email address will not be published. Required fields are marked *

HTML tags are not allowed.

883,253 Spambots Blocked by Simple Comments