Hexactinellid (glass) sponge reefs are unique biogenic habitats found along the Northeast Pacific margin of North America. Seabed surveys with remotely operated vehicles and drop cameras revealed expansive dead areas, with few or no living glass sponges observed on reef surfaces, in some of the reefs. We collected sediment cores and undertook radioisotope age dating using Pb-210 and Cs-137 methods in dead or largely dead areas within three glass sponge reefs along the coast of British Columbia, Canada (Hecate Strait, Chatham Sound, and Howe Sound), to determine whether the sponges died due to environmental or anthropogenic causes. Our results indicate that these reef areas stopped growing within the past 70 years, and at least one probably died within the past 20 years. The historical spatial patterns of fish and invertebrate trawl and trap fisheries correlate well with heavily damaged or destroyed reef areas, suggesting that sponge-free reef surfaces and finely broken and fragmented reef areas are likely a consequence of modern bottom-contact fishing. Our findings support the need for protection of glass sponge reefs from human activities and shed light on the possibility of glass sponge reef recovery. • Some of the ancient glass sponge reefs in Canada exhibit expansive dead areas • Core samples were collected to determine the timing and cause of demise of 3 reefs • Radioisotope methods indicate the reefs died within the past 70 years • Historical fishing pressure maps suggest bottom-contact fishing is the likely cause • The longevity of glass sponge reefs requires protection from human impacts
Dunham et al. (Sun,) studied this question.