SOG: Glass Sponge Reefs

My Research Interests

I study the ecology of glass sponges (Porifera, Hexactinellida) - common animals throughout the world's deep oceans (> 200 m). On the continental shelf and fjords of British Columbia Canada, hexactinellids are particularly abundant and diverse. Western Canada is also where they form the world's only glass sponge reefs - city sized, some 9000 years old, and built entirely by 2-3 species of hexactinellids. In the Strait of Georgia, recently discovered reefs (2004-2008) represent tractable and accessible model systems that allow us to study sponge reefs at the ecosystem level.

For my Master's, I empirically established the biological patterns and processes that define the “glass sponge reef” system. During my degree I took a multiscale, multifaceted approach to examine this unique ecosystem.

Themes and Questions I have attempted to address:

(1) Spatial Patterns of Glass Sponges

Most of a sponge reef, up to 21 m, is buried underneath sediments. It is the upper 1-2 m of exposed sponges, the living component of a reef, that creates the added seafloor complexity which creates habitat for other animals such as fish and crustaceans. With recent interest in establishing entire glass sponge reefs as marine protected areas (MPAs)1, it has become increasingly important to understand the biology of the live sponges because they are the biological foundation of the entire ecosystem.

By mapping out the sponge populations in a reef, this establishes a biological baseline to allow temporal patterns and processes to be addressed in future monitoring. This also creates the empirical foundation required to address quesitons regarding how such dense communities of sessile suspension feeders could be affecting their local environment.

Questions I have attempted to address:

Published in:

Chu JWF, Leys SP (2010) High resolution mapping of community structure in three glass sponge reefs (Porifera, Hexactinellida). Marine Ecology-Progress Series 417:97-113.

Chu JWF, Leys SP.The dorid nudibranchs, Peltodoris lentiginosa and Archidoris odhneri, as predators of glass sponges. Invertebrate Biology (accepted)


(2) Glass Sponge Silica

Sponges are currently not considered important players in biological silicon cycling in the ocean. Largescale Si cycling is entirely contributed to diatoms which rapidly turnover biogenic silica (bSi) into dissolved silicates (dSi) in surface waters. Glass sponge reefs, however, represent city sized areas densely covered by sponges that are 80% bSi by drymass. In order to illustrate the potentially overlooked massive reservoirs of bSi locked into the large sponge populations, we have set out to determine the Si flux and establish a silicon budget for a glass sponge reef.

Questions I have attempted to address:

Published in:

Chu JWF, Maldonado M, Yahel G, Leys SP (2011) Glass sponge reefs as a silicon sink. Marine Ecology-Progress Series 441:1-14. (Feature Article).




(3) Trophic Patterns of Glass Sponges

Glass sponges are extremely selective suspension feeders on water column bacteria. The high densities of the main reef forming sponge, Aphrocallistes vastus, in the reefs would suggest that food has an important role in sustaining the sponge populations. We use stable isotopes analysis (carbon & nitrogen) to examine the trophic patterns that are characteristic of A. vastus, and to determine if this signature is different between populations and locations.

Questions I have attempted to address:

I am currently a Phd Student at the University of Victoria. Please e-mail me at jwfchu@uvic.ca