What are these green jelly blobs?

The Question: I saw these bright green jelly like blobs in Easdale Tarn, in Cumbria, England. The blobs ranged in size from about 1.5 cm (1/2 inch) to 4 cm (1 ½ inches) cm.  There were quite a few of them, some floating in the water and a couple attached to rocks. What are they? Are they some sort of egg?

Submitted by: Alison, Cumbria, England

The Short Answer: These blobs are made by a colonial microscopic single-celled protozoan called Ophrydium versatile. They can be found all over the world in fresh water. The individual cells line up side by side in the “blob” and attach themselves to a jelly-like substance they secrete. They are symbiotic with microscopic Chlorella algae which live inside the Ophrydium cells and give the blob its green color. This page shows a number of pictures of the blobs in the water:


This brief youtube video clearly shows the hundreds of green Chlorella cells living inside the Ophrydium cell:


This one shows the cilia that Ophrydium uses to gather particles including bacteria, other organisms and detritus from the water:


ophrydiumMore Information:  Ophrydium cells reproduce by dividing.  As the number of Ophrydium cells increase, they remain on the outside of the growing blob, and the interior, which is now empty of Ophrydium cells, becomes a watery gel. This soupy interior gel can become home to all kinds of microorganisms such as mastigotes, euglenids, chlorophytes, heliozoans, diatoms, bacteria, rotifers, nematode worms, other ciliates, and even tiny crustacean copepods, leading some to compare Ophrydium blobs to a floating zoo of tiny creatures.

Ophrydium is always found with its algal symbionts. The Ophrydium structure probably helps the algae gather light efficiently. The Ophrydium also shares nutrients like nitrogen it gains from the bacteria and other particulate material it sweeps from the water with its cilia. In return, the algae supplies Ophrydium with sugars it makes through photosynthesis. During the summer, the majority of the carbon assimilated into the colony comes from photosynthesis. In the winter, the colonies remain active, but most of the carbon assimilated comes from the organisms Ophrydium gathers from the water column.

Other Common Blobs: One of the most common questions to AskaNaturalist.com is “What is this blob I found in the water?” I’ve written about Bryozoan blobs and amphibian egg masses. Other possibilities for fresh water blobs include snail egg masses, fish egg masses and freshwater jellyfish. Keep those blob questions coming!


Thanks to Ophrydium expert and University of Saint Joseph professor Mark Johnson for his help identifying these blobs and for the information in his dissertation Seasonal Changes in Distribution and Tropic Mode of the Mixotrophic Ciliate, Ophrydium versatile, in a Freshwater Pond Ecosystem.

Sand-Jensen, K, Pedersen, O, & Geertz-Hansen, O. (1997). Regulation and role of photosynthesis in the colonial symbiotic ciliate ophrydium versatile. Limnology and oceanography, 42(5), 866-873.

Duval, B, Margulis, L. (1995). The microbial community of ophrydium versatile colonies: endosymbionts, residents and tenants. Symbiosis, 18:181-210.

Cite this article as: Pelletier, TC. (August 16, 2012). What are these green jelly blobs? Retrieved from http://askanaturalist.com/what-are-these-green-jelly-blobs/ on July 3, 2020.

21 thoughts on “What are these green jelly blobs?”

  1. Alison,
    Thanks for saying that! And thanks for the great question. You’re helping me to become Blob Central on the web.


  2. Pingback: Ask a Naturalist.com » Donut blob that stumped the experts …
  3. Tom: I have found a plethora of these green blobs in a constructed wetland bog in central Massachusetts, USA. I did not collect any since I honestly thought they might have simply been empty salamander egg masses. However, upon looking carefully at my digital photos, I believe they are very likely Ophrydium versatile …. Some appended to underwater stems of aquatic plants are unto 1.0 meter long and as wide as 10-15 cm. I would like to send you a photo or two…to see what you think. Regards… Mal Gilbert

  4. Tom: I am a wetland scientist here in the US and have had considerable experience over the last 40 years (here in US and internationally). I was simply flummoxed when I encountered the “blobs”… I will be pulling together a PDF file too images to send to you via email. It will include the “setting” and reasonably good close-ups of the “blobs”. As my spouse has suggested, I really need to collect a small sample to assess with one of our microscopes…. In any event, if Ophrydium versatile, I believe it would be important to document the location in the US. Thanks…. I hope to have the PDF ready to send in the next 1-3 days. Cheerio…. Mal G.

  5. Hi Tom I have a small pond, 3m x 5mx 1m deep, which is full of Ophrydium versatile. I would like to treat the water to eliminate them, but don’t want to hurt the salamanders and potential frogs.
    We have pond supplies who sell algae clearing products but I’m not sure if it will clear Ophrydium.
    Thus far I have emptied out some of the Protozoa onto wet areas near the pond not wishing to kill the blobs just move them from the pond.
    Any thoughts would be most helpful.

  6. Hmmm … that’s a tricky one. Your hesitation to just applying algae killing products is probably valid, since any toxic products often kill “non-target” creatures. And the organisms that make ophrydium work are similar to the ones that form the bottom of the food chain that sustains the salamander and frog tadpoles. So physical removal the way you’ve been doing is probably the safest thing. Is it an issue of aesthetics?

  7. Yes Tom it is aesthetics but also would like to see what’s under the blobs as they cover the top completely.
    We have another pond right next to this one, same size but on a lower level. It has lots of lily pads so in summer it doesn’t have much of a bloom of anything (except lilies). And it doesn’t have any Ophrydium. But both have lots of dead leaves to be cleaned out (leaving the muck by the edge of the pond so creatures can crawl back).
    I’ve read that some folks who have aquariums use a low solution of hydrogen peroxide(3%) to get rid of algae but not the fish. However I take your point regarding creatures lower on the food chain.
    Guess I’ll have to clear the pond as best as possible and plant lots of lily’s.
    Thanks Tom.
    P.S. given the problem with micro plastics in our seas, do you eat fish?

  8. Teresa, I didn’t mean to imply that aesthetics isn’t important. You put in a backyard pond because you want to see stuff, not because you want to have a slimy puddle. 🙂

    I keep aquariums. I could let algae grow all over the glass and the fish would probably like it better, but then I wouldn’t see anything.

    The lilies might help. Do you have a water test kit? You might have too much nitrogen or phosphates, or both, which can encourage algae and probably ophrydium. The lilies would compete with algae for the nitrates and phosphates.

  9. Thanks Tom I do have a test kit and will test the water in both ponds. And I’ve bought some small pond netting which will be going over the ponds come autumn.
    Look forward to following your site.
    Best wishes

  10. Hi, I have a 12 acre,very deep (45 ft. plus) lake and in 28 years have never seen these blobs before.
    What is the cause? Some are floating, some are suspended and some are attached to weeds on the bottom. We had dominate N.W. winds which blow into our shore leaving a six foot wide row of this on the shore. What could be the cause?

  11. Yes… appears that once again the Ophrydium are the culprits. Their propensity to filter and clear the water column of bacteria might, however, be of comfort to those fearing the 1950’s invasion of “The BLOB”….. Well done Tom.

  12. Discussion of the problem is good. Solution ?
    Should we leave the “blobs” alone, remove them, chemically (?) treat them ? Are they disruptive to the ecology; fish or plant life.

  13. Hi Tony, they are a natural and harmless part of aquatic ecosystems. You don’t need to do anything to them. Tom

  14. I’m in entire agreement with Tom… if Ophrydium versatile, they are actually helping to filter and clean-up the water column. I didn’t see the photos, but they certainly sound like Ophrydium.

    Mal Gilbert

  15. I have been citing your most-helpful post about Ophrydium versatile in regards to an enormous transparent but greenish jelly blob I found in a shallow bay of a pristine Adironack Lake (Lens Lake), and I’m wondering now if I was correct to do so, since most folks seem to report much smaller blobs than the one I found, which was a good six feet long by two feet across and perhaps 8 or 10 inches deep. Could mine be anything else BUT Ophrydium? You can see a photo of the one I found on my blog: https://saratogawoodswaters.blogspot.com/2017/09/lens-lake-early-autumn.html

  16. The ones you show are very similar to the masses I have found in waters near Springfield, Massachusetts. Although they appear as a much larger mass, I think they are clustered individual “colonies”… very similar to the way I found them in Massachusetts. I am still inclined to call your find Ophrydium versatile.

    (PS> awesome photos of that area!)

  17. Hi Tom,
    We found some round, hollow sac-like, green organisms in a lake in Island Falls, Maine. They hold their shape when they are out of the water and feel quite tough. They don’t look jelly like. I was assuming they were just algae until I saw this page. They were free floating on the bottom in a shallow and warm part of the lake. My husband has been noticing them for years. I will send you some photos of them not in their native environment. One of my friends suggested they might be a Bryozoan colony, but they don’t quite look like that either.

  18. Are these dangerous for the life of the pond? We have lived on our pond in Plymouth, MA for 9 summers and this is the first time we have seen these. And, there are plenty of them. Thanks!

Leave a Reply

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

1,204,620 Spambots Blocked by Simple Comments