[Coral-List] Strange algae reported by divers

[Bastiaan Vermonden]

Dear coral-listers,

Thanks everyone for helping with the identification. The two main
suggestions are:

Its a sponge
Possible species
       Terpios hoshinota
       Trididemnum

Or Its a tunicate
       didemnid tunicate

Most people seem to suggest its a sponge. I would like to restate that I
found this question in a Linkedin discussion and so I am unable to do any
kind of field analysis (unfortunately). I am currently not working on coral
reef related topics or anywhere near a tropical destination. (also nowhere
near coldwater coral formations)

But I would like to pose some additional questions because I have not come
across a lot of literature regarding sponges or tunicates killing corals.
Most literature on coral reef degradation refers to bleaching, algae
overgrowth, diseases, COTS, etc.

So my question or maybe start of a discussion if people are interested is:

1. Are these sponges and/or tunicates a significant contributor to reef
degradation (a quick search brought up this
http://www.wcs.org/press/press-releases/microbes-sponges-worms.aspx)?
2. If this is a (major) contributor to reef degradation is the occurence of
this phenomena increasing? (Thomas Goreau suggests it is)?
3. What are the (hypothesized) causes of this phenomena? (eutrophication?)

And since I know there are people with blogs, magazines etc reading this,
should they report on this and if so how?

Kind regards,

Bastiaan

PS.

My apologies if this has all already been thoroughly discussed, for me this
is new.