Discovery of a “Living Dinosaur”: Globally unique modern hexactinellid sponge reefs off British Columbia, Canada

Globally unique hexactinellid sponge reefs occur on the continental shelf off British Columbia, Canada. They cover about 425 km^sup 2^ of seafloor on the continental shelf off British Columbia (Canada) in water depths between 165 and 240 metres and occur on a low-angle deep shelf, iceberg scoured se...

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Bibliographic Details
Published in:Facies 2001-01, Vol.44 (1), p.265-282
Main Authors: Krautter, Manfred, Conway, Kim W., Barrie, J. Vaughn, Neuweiler, Matthias
Format: Article
Language:English
Subjects:
Aphrocallistes vastus
Continental shelves
Environmental conditions
Farrea occa
Marine
Ocean floor
Population density
Reefs
Refugia
Sedimentation rates
Submarines
Trawling
Water depth
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Summary:Globally unique hexactinellid sponge reefs occur on the continental shelf off British Columbia, Canada. They cover about 425 km^sup 2^ of seafloor on the continental shelf off British Columbia (Canada) in water depths between 165 and 240 metres and occur on a low-angle deep shelf, iceberg scoured seafloor, characterized by very low sedimentation rates and very stable environmental conditions. The sponge bioherms are up to 19 metres high with steep flanks, whereas the biostromes are 2-10 metres thick and many kilometres wide. They all consist of dense populations of only seven hexactinellid species. Three of them, all hexactinosan species (Aphrocallistes vastus, Heterochone calyx, Farrea occa) are the main frambuilders, composing a true rigid framework of sponge skeletons encased in a organic rich matrix of modern clay baffled by the sponges. Growth rates of hexactinosan sponges range in the order of 0-7 centimetres per year. The base of the oldest sponge reefs date from approximately 9000 years b.p. Different invertebrate and fish faunas occupy the reefs than occur on adjacent seafloor areas and some species appear to use the sponge reef complex structures as refugia where they can hide. Sidescan sonar data and direct observation by manned submersible clearly show that large areas of sponge reefs have been heavily damaged by seafloor trawling in the past decade. These unique extant siliceous sponge reefs can be used as a modern analogue for a better understanding and interpretation of fossil siliceous sponge reefs, known from many ages and many locations world wide.[PUBLICATION ABSTRACT]
ISSN:0172-9179
1612-4820
DOI:10.1007/BF02668178