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Marine Ecology Progress Series

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MEPS 283:133-149 (2004)  -  doi:10.3354/meps283133

Patterns of glass sponge (Porifera, Hexactinellida) distribution in coastal waters of British Columbia, Canada

S. P. Leys1,*, K. Wilson2, C. Holeton2, H. M. Reiswig2, W. C. Austin3, V. Tunnicliffe2

1Department of Biological Sciences, CW 405, University of Alberta, Edmonton, Alberta T6G 2E9, Canada 2Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada 3Khoyatan Marine Laboratory, Sidney, British Columbia V8L 4X3, Canada

ABSTRACT: Glass sponges are enigmatic members of the deep-sea fauna that inhabit shallow waters in only a few locations world-wide. In order to understand what factors influence the distribution of glass sponges, patterns of distribution and abundance of reef and non-reef forming hexactinellids in fjords of British Columbia, Canada, were analyzed from photographs and transcripts recorded on dives undertaken by the ‘Pisces IV’ manned submersible during the 1980s. Hexactinellids are widely distributed throughout all fjords from 16 to 650 m depths, and in some fjords abundances reach 240 individuals in 10 m2. In all fjords hexactinellids were most abundant at depths of 20 to 260 m, even where water depths exceeded 500 m. Glass sponges were rare in regions of inlets where oxygen levels fall below 2 ml l-1, or in areas of high sediment deposition. Highest abundances coincided with water conditions of high dissolved silicate, low light, temperatures between 9 and 10°C and low suspended sediments. Extensive glass sponge skeletons in the inner basin of Howe Sound reflect past stress in this fjord that may include oxygen deficit, sediment loading from a mine and contamination from industrial sites. The observations from ‘Pisces IV’ suggest that glass sponges may be sentinel species for current and past seawater conditions in coastal British Columbia.

KEY WORDS: Glass sponges · Hexactinellida · Fjords · Silica · Sponge reefs

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