An introduction to glass sponge reefs

by Amanda Kahn

Okay, as far as we know, glass sponges do not form reefs offshore of Barkley Sound, but the same species that form the reefs in these videos do appear as solitary individuals near Bamfield, and in any case, the idea that sponges form reefs is so awesome that this video should be posted here anyway.  Check out the first installment of a series of short videos about glass sponge reefs, put together by Sameena Sherman from the Leys lab at the University of Alberta.  A transcript of the video can be found below.

Transcript of the video:

Fossils suggest that glass sponges were established by the Late Proterozoic era. In the Jurassic, there were large reefs formed of glass sponges that covered the Northern shore of the Tethys Sea, which is now the area representing Europe and Eastern Canada. Sponge reefs, as a biogenic structure, were initially thought to be extinct until the discovery of the reefs in the Pacific Northwest.

Most glass sponges live in depths greater than 500 metres. Off the coast of British Columbia in the North Pacific, vast reefs spanning hundreds of square kilometres live in shallower depths of approximately 200 metres. This depth is speculated to be favourable for sponge reefs because of high silica content, high food content, high water flow, and cold temperatures reminiscent of the deep sea.

Glass sponges possess a unique silicon dioxide skeleton and syncytial tissue formed by fused embryonic cells. They are typically vase, plate, or tube-shaped.

There are two structural types of glass sponges. Lyssacine sponges have a loose spicule skeleton and are non-reef-forming. Dictyonine, on the other hand, can form reefs due to a fused spicule skeleton. Only 3 species make up reefs; they are Aphrocallistes vastus, Heterochone calyx, and Farrea occa. These species are found throughout the Pacific as individuals; it is only in the northeast Pacific that they form reefs.

You can learn more about glass sponges and see more videos at our website: http://www.biology.ualberta.ca/leys_lab/.

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