Distribution, biodiversity, and function of glass sponge reefs in the Hecate Strait, British Columbia, Canada

• Author / Creator

  Law, Lauren, KP

• Reefs of glass sponges (Porifera, Hexactinellida) off western Canada were recently established as a marine protected area (MPA), however effective management and monitoring of this MPA is hindered by a lack of baseline data about reef distributions and biodiversity. MPA boundaries were established around reef polygons mapped using multibeam acoustics. Multibeam technology does not differentiate between live, dead, and buried portions of sponges. To ground-truth past multibeam mapping, a remote operated vehicle (ROV) was used to conduct fine-scale photographic surveys at three reef sites in the Hecate Strait, British Columbia. I performed semivariogram analyses and spatial interpolations to produce maps of reef distributions. The relationship between glass sponges and associated megafauna (> 2 cm) was analyzed from ROV images. Polygons mapped by multibeam acoustics represented the densest areas of sponge with ~10% of live and dead sponges found outside these polygons, while the remaining area was bare substrate (i.e. buried sponge or patches of mud). Glass sponges were patchily distributed in the reefs and spatially dependent at 28 to 36 meters. Although total megafauna density was significantly higher in the presence of glass sponges, glass sponges did not correlate with an increase in all taxa. Megafauna associations in the reefs occurred at a taxon-specific level and sponge reef structural complexity was found to be an important influence on reef community structure. The reefs also hosted numerous non-reef forming sponges, which until now have been previously overlooked. Molecular analyses and taxonomic classification were used to identify multiple encrusting sponges in the reefs, of which one was a new cryptic sponge in the genus Desmacella. This study garnered baseline data for Fisheries and Oceans Canada to improve their capacity for monitoring changes in the status and health of sponge reef ecosystems in Canada.

• Subjects / Keywords

  • Hecate Strait
  • Sponge reefs
  • Glass sponges
  • Glass sponge reefs

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3TX35N3S

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.