[Coral-List] Fwd: Mat tunicate problem?

Helen Sykes helen at marineecologyfiji.com
Thu Jan 17 02:05:46 EST 2008

Sounds like a Didemnum species of Ascidian (Tunicate).

We have seen immense overgrowths on degraded rubble reefs. Natural predators
are nudibranchs etc. I used to think it was the end of a reef as it
overgrows corals, algae etc, but we have seen huge mats disappear over a
matter of weeks, for reasons unknown. Probably best to leave it alone -
peeling off individuals only allows them to spread in the current.

Helen Sykes

marine ecology
Fiji's leading company for Coastal & Marine Ecology Assessments 
PO Box 2558, Govt Buildings
Suva, Fiji Islands
t: +679-336-3625 / +679-359-2136
e: helen at marineecologyfiji.com 

-----Original Message-----
From: Alex Brylske [mailto:Brylske at aol.com] 
Sent: Thursday, January 17, 2008 5:44 AM
To: coral-list coral-list
Subject: [Coral-List] Fwd: Mat tunicate problem?

Received this letter from a reader, and would appreciate some insight from
the group. Is he talking about some kind of colonial tunicate?  
Sorry, he didn't send any images.


Alex Brylske, Senior Editor

4314 SW 18th Place
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Phone: 239-471-7824
Cell: 954-701-1966
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E-mail: brylske at aol.com
Website: www.dtmag.com

Begin forwarded message:

> From: Roger Dunton <roger335 at comcast.net>
> Date: January 16, 2008 12:26:47 PM EST
> To: Alex Brylske <brylske at aol.com>
> Subject: Mat tunicate problem?
> Alex,
> While leading a group in Cozumel this Christmas, I met a lovely couple 
> who pointed out what we believe may be a problem infestation of the 
> coral reefs. I am including their description to see if you are aware 
> of this and perhaps what might be done. They referred to it as a "MAT 
> TUNICATE", but it was unlike any tunicates of which I am aware.
> "First of all, we are not sure of the name, it was given to us by a 
> dive master in Belize on Turneffe Island.  We have looked through the 
> name on internet but did not find anything close to it.
> Whatever its name, this algae is light grey - a bit greenish, and when 
> taken to surface it is actually a pale pink.  It is thick and feels 
> rather soft to touch, like leather.  It covers the coral like a 
> blanket.  Actually when you look close, it seems to start with a small 
> drop, and you can see several drops like sprayed from above.
> Each drop seems to develop into a blanket that covers the whole coral 
> head it started on, and grows along the stems of fans and sponges 
> until it covers it entirely.
> The dive master in Belize indicated that the algae should be removed, 
> or at least untucked from the coral head on the edges to stop its 
> growth.  When you do this, it is sometimes easy and comes in large 
> pieces, sometimes it breaks into small crumbs.  Below the blanket, the 
> coral is dead, and it seems there is only rock.  There are often thin 
> spiders with long legs or long worms between the rock and the algae.  
> The algae is soft when taken off the coral, and when it dries on the 
> surface it becomes rigid.
> We have seen it a lot in Belize on the East side of Turneffe Island, 
> and we start to see it a lot in Cozumel, at about any depth.  We have 
> not been able to observe a pattern, but I thought there was maybe more 
> of it in shallower waters.  The weird thing is that when you start 
> looking for it, you see it a lot whereas if you are not looking, you 
> don't notice it so much.
> I would be interested in learning what it is, and what should be done 
> with it: remove it and dispose of it at surface, or just untuck it, or 
> leave it alone?
> Thank you for any light you might shed on this."
> -Roger Dunton

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