1. Sponge Reefs M. Krautter, U. Stuttgart Sponge Reef Project, 1999 http://www.porifera.org/a/cif1.htm

2. Fig 4-8 Sponge reefs occur on the continental shelf of the North Pacific

3. bioherms 70 m high http://www.brookes.ac.uk/geology Reefs: Carbonate bodies Contain fossil organisms Biologically ‘influenced’ Rigid framework Some are buried by sediment Others have positive relief Bioherms – mounds (lens shaped) Biostromes – flat (laterally extensive)

4. Ancient sponge reefs

5. J. Ghiold, New Scientist 1991 Sponge reefs during the Jurassic Location of Jurassic reefs relative to modern Europe

6. Distribution of the main reef forming glass sponges

8. Glass sponges: Deep water animals (> 500 m usually) Skeleton of glass – SiO 2 Soft tissue is largely multinucleate (syncytial) Can send electrical signals (like nerves) These signals shut down the feeding current Respond to mechanical stimuli – including sediment Two principal types: fused skeleton; loose skeleton

9. Glass sponges have a skeleton of silica dioxide (SiO 2 ) = nearly pure glass In reef-forming glass sponges this is fused into a rigid scaffold as shown at right

10. The tissue of glass sponges is largely a multinucleate giant cell. The top image shows tissue growing in a petri dish The bottom image shows masses of nuclei (blue) scattered around massive microtubules (red) – the length and straightness of the microtubules confirms that the sponge is syncytial.

11. The sponges live in a very turbid environment and can filter lots of sediment

12. Thermistor flow meter – recording pumping (flow) Sponge osculum Water current Normal ‘arrests’ of feeding Sediment added Pumping Not Pumping Glass Sponges respond to sediment in their incurrent water by shutting down their feeding current

13. What have we learned about the reefs?

14. Core Formed on boulders at the edge of ice berg scours 8-10,000 years ago Northern reefs are 5-21 m thick Individual sponges are 50-220 years old The reefs are up to 6000 years old! What have we learned about the reefs?

15. Glass sponges are affected by their environment. It is thought that the following conditions are required for growth of a sponge reef: Low temperature (7-12 o C) Low light High dissolved silica (>50 uM) Low sediment – juveniles need firm substrates to attach to.

16. Trawl marks have been found through one reef Conservation

17. Summary: 1.Glass sponges are abundant in deep water world wide but can be found in shallow water in 4 locations 2.One type of glass sponge has a fused skeleton. These sponges form reefs by juveniles settling on the skeletons of adults. Reefs = bioherms. 3.Sponge reefs were common during the Jurassic, when they formed a vast band across an area that is now much of Europe. These leave a fossil trace that can be found in rocky outcrops in Spain, France and Germany. 4.Today living sponge reefs are only found in Canadian Pacific continental shelf waters (<500m deep). 5.Canadian sponge reefs are up to 6000 years old. The first sponges probably colonized ice berg scours after the glacial retreat on the Pacific Coast. 6.The reefs are now approximately 6 m high – consisting of sponge skeletons cemented together with sediment. 7.The reefs likely need low light, cold water, high silica levels, and low sedimentation to survive; (juveniles settle on the skeletons of adults). 8.Some of the reefs have been endangered by trawl fisheries which drag large nets held open by heavy doors through the reefs.