View Full Version : What causes the powder blue splashes on rocks at St Catherines?
alexmaclennan
28-12-08, 15:23
I dived St Catherines 2 reef today - the one with the small rocky jetty on the turnoff before the Bottle Bank
Every now and then I came across powder blue splashes ? algae ? bryozoan on the rocks on the boulderslope. Most of the rocks have pink encrusting algae and keelworm casts. The blue stuff is always closely applied to the rock but fairly easily scraped off. What is it?
alex
Dive Tramp
28-12-08, 16:30
Is it this
http://i184.photobucket.com/albums/x33/DiveTramp/DSCF2521-1-1.jpg
Or this
http://i184.photobucket.com/albums/x33/DiveTramp/DSCF2054.jpg
Coz I've been trying to find out what the first one is for ages, then I go and find the second one too. I haven't managed to find an ID for either one yet.
Edit, might have found it now. Possibly Hymedesmia paupertas, This sponge grows as a small thin sheet, typically in patches of only 1-2cm in diameter. The colony usually has a very irregular outline, giving the appearance of several separate patches. The colour of this sponge is a very distinctive bright blue or green. The surface has small pore sieves. Info courtesy of http://www.habitas.org.uk/marinelife/index.html
Still no ID for the first one tho...
alexmaclennan
28-12-08, 18:20
Definitely looks like picture no 2,
I did not see any pores and it could be up to 5 or 6cm diameter tho more usually 2 to 3cm diameter
alex
I think it may be a star sea squirt or Botryllus schlosseri. Its a colonial sea squirt and grows in groups. I'm referring to the first pic. Heres another example but they do come in a variety of colours
http://www.glaucus.org.uk/StarAscidian065.jpg
Dive Tramp
29-12-08, 12:32
You're a star Triplefin! Well done! Yeehaa finally, only been looking for a year.:eek:
When are you coming up North for some good diving then?
When are you coming up North for some good diving then?
You'd have trouble keeping me away. I usually come up several times a year and spend all of august north of the border. Best diving in the UK :)
If it's the stuff in the 2nd pic, that looks like Blu-Tac, there's lots of it on the wall at Stallion Rock too.
It's a form of sponge.
I've not tried to find the name.
There's not much of it about and the patch at St Cats is the largest I've seen.