To assess the extent and nature of the impacts on glass sponges and associated community, we collected video and still imagery
along fixed transects using a Remotely Operated Vehicle (Phantom
ROV HD2 þ 2, Deep Ocean Engineering) twice a year for four years
following cable installation. Our study followed a 2-way
(treatment time) design. Transect locations were chosen by
overlaying the reef perimeter mapped by the Canadian Hydrographic
Service using multibeam bathymetry data (K. Conway,
Natural Resources Canada) and cable crossing locations provided by
the BCTC. Three cable transects followed the three cables crossing
the reef polygon. Control transects were plotted parallel to cable
transects at a distance of approximately 100 m (Fig. 1). Cable
transects were 108 ± 23.6mand control transects were 125 ± 7.4 m
long (mean ± SD, n ¼ 3). Three 2 2 m index sites were randomly
chosen along each transect and each marked with two numbered
hard trawl floats (diameter 95 mm) attached to iron weights and
carefully positioned between the living glass sponges. Cable index
sites were laid out in away that the cable ran through the middle of
each site. The resulting six transects and 18 index sites were surveyed
twice a year, in spring and fall, between October 2008 and
February 2012.