Seagrass-Sponge Interactions

The sponge Halichondria melanadocia growing around the base of turtle grass (Thalassia testidunim).

The sponge Halichondria melanadocia growing around the base of turtle grass (Thalassia testidunim)

Last summer I started noticing this black sponge growing around the base of turtle grass (Thalassia testidunim) shoots, in some cases covering a significant portion of the seagrass and decided to try and quantify the interaction between turtle grass and this sponge (Halichondria melanadocia). We know that sponges can release significant amounts of nitrogen in a form algae and seagrass can use (if you find this interesting- see this review for a thorough discussion of how sponges process nutrients). Last summer, labmate Elizabeth Stoner and I conducted surveys at several sites around Abaco looking at seagrass density and Halichondria densities, and collected samples to look at the nutrient content of seagrass shoots with and without sponge growing on them.


We didn’t find any significant difference between seagrass with and without a sponge growing on it. This was surprising because we didn’t even see differences you’d expect if all the sponge did was shade the seagrass. So this summer we’ve set up an experiment to determine if seagrass shoots that have a sponge growing on them grow more slowly than seagrass shoots without a sponge. We also measured the percentage of the seagrass shoot being shaded by the sponge and attached pieces of dead sponge covering approximately the same percentage to a seagrass shoot nearby (see picture below). This experiment will allow us to determine if the sponge is simply not covering enough of the seagrass shoot to have an effect, if the sponge is shading enough of the shoot to slow growth, or finally if the sponge is shading the shoot enough that growth should be slowed but the sponge is providing something to the seagrass to offset the effects of shading. We’ll go back and collect the seagrass we marked in two weeks and will let you know the results.





By | 2017-12-01T14:03:46-05:00 June 23rd, 2013|Categories: Nutrients, seagrass, Uncategorized|4 Comments

About the Author:



  1. Avatar
    Cristina Diaz October 20, 2013 at 10:16 pm

    Dear Stephanie, I wonder what did you find through your experiments.

    Nice experiment by the way.

    Take care,


  2. Avatar
    Stephanie October 21, 2013 at 9:21 am

    Hi Cristina-

    It’s nice to hear from you! I will be presenting on this stuff at the World Sponge Conference coming up. Will you be there? If not, I’ll post a pdf of my talk after I give it.


  3. Avatar
    Meutia Samira Ismet January 5, 2014 at 2:31 am

    Dear Stephanie, that’s an interesting experiment you have on sponge. I’m interest to know what did you have through the experiment. I’m doing my research on sponges and it’s microbial symbionts in the seagrass area. And found quite similar sponge like you have there, by the way I’m doing it in Indonesia. And I’m really hoping that we can have a nice discussion on it.
    Looking forward for your respond.
    Thank you

    Warm regard from Indonesia,

  4. Avatar
    Stephanie January 5, 2014 at 9:23 am

    Hi Meutia-

    That is great. There aren’t all that many of us working on sponges in seagrass. If you email me, I can send you a copy of the talk I gave at the world sponge conference and we can talk about our research in more detail. My email address is

    Looking forward to hearing from you!


Comments are closed.