Status of the glass sponge reefs in the Georgia Basin

• Published in: Marine environmental research Vol. 66; no. suppl.; pp. S80 - S86
• Main Authors: Cook, Sarah E., Conway, Kim W., Burd, Brenda
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-01-2008; Elsevier science
• Subjects: Animals; Aphrocallistes vastus; British Columbia; Continental shelf; Ecosystem; Effects – bottom trawling; Environmental Monitoring; Fisheries; Fishes - physiology; Geologic Sediments; Georgia Basin; Glass sponge reefs; Hexactinellida; Marine; Megafauna; Multibeam; Oceans and Seas; Porifera - physiology; Reef status; Relative abundance; Rockfish; Sebastes; Sidescan sonar; British Columbia; Canada, British Columbia; INE, North America, Georgia Strait; INE, Canada, British Columbia, Georgia Basin; Georgia Basin; Hexactinellida; Megafauna; Continental shelf; Relative abundance; Reef status; Sidescan sonar; Rockfish; Effects – bottom trawling; Glass sponge reefs; Multibeam; Life Sciences
• ISSN: 0141-1136; 1879-0291
• DOI: 10.1016/j.marenvres.2008.09.002

The purpose of this paper is to describe the status and general faunal composition of sponge reefs in the Georgia Basin (GB), British Columbia, Canada. Fourteen distinct deep-water glass sponge (Hexactinellid) reefs have been mapped using multibeam bathymetry and sidescan sonar in the GB. Seven of these have been surveyed visually using video from remotely operated vehicles (ROVs). Analysis of video data indicated that three reefs were undamaged, two were damaged and the other two were damaged but potentially recovering. The nature of the damaged reefs, with large areas of scattered dead sponge skeleton fragments and few live reef-building sponges (
Aphrocallistes vastus and
Heterochone calyx), as well as video evidence of tracks suggest they were damaged mechanically by mobile fishing gear.
Relative abundance of the megafauna associated with the reefs is discussed in the context of oceanographic conditions, such as sediment accumulation and organic flux, as well as overall reef status. Of particular interest for fisheries conservation efforts in the area was the fact that one undamaged reef in the southern GB showed higher taxonomic richness and abundance of rockfish (
Sebastes spp.), both adult and juvenile, compared to an adjacent damaged reef. This result suggests that undamaged reefs may act as refugia for these endangered stocks.