Ancient Glass Sponge Reefs

Glass sponge reefs were believed to have become extinct 40 million years ago. However, in 1984, Glen Dennison discovered glass sponge reefs in the depths of Howe Sound while doing research for his book on diving.

His discovery launched a private citizen effort to locate and protect the reefs, eventually resulting in the DFO protecting seventeen different sites in Howe Sound and the Hecate Strait. The three reefs within the Hecate Strait and Queen Charlotte Sound Marine Protected Area cover 1000 km2.

The discovery team led by Glen Dennison became the first humans to ever set eyes on a living glass sponge reef. It is estimated that there are more than 20 glass sponge reef sites in Howe Sound alone.

How are Glass Sponges Formed?

As sponges grow, they filter silica out of the water and use it to create a lattice-like exoskeleton called spicules. When sponges die, juvenile sponges and sediment attach to the dead skeletons, which is how a reef complex forms. Some reefs have been identified as having grown over twenty meters in height.

What Role Do Glass Sponges Play in a Marine Ecosystem?

The filtering capability of glass sponge reefs is so efficient that the Howe Sound reefs filter all the sound’s water in three months. Glass sponge reefs also provide essential habitat for several marine species, such as zooplankton, sea stars, urchins, salmon, spot prawns, rockfish, herring, halibut, and sharks.

Scientists have dated the Howe Sound reefs to around 9,000 years old. This means that these ancient yet living reefs started to form just after the last ice age. Photo credit: Canadian Geographic

Here’s a full breakdown of how they contribute to marine ecosystems:

1. Habitat Formation: Glass sponges provide habitat and shelter for a variety of marine organisms, including small fish, shrimp, and other invertebrates. The complex architecture of glass sponge reefs offers protection from predation and serves as a substrate for attachment and colonization.

2. Filter Feeding: Like all sponges, glass sponges are filter feeders. They draw in and filter water through their porous bodies, capturing tiny particles, plankton, and organic matter. This feeding behavior can help maintain water clarity by removing suspended particles, and it contributes to nutrient cycling in the ecosystem.

3. Calcium Cycling: Glass sponges absorb and incorporate calcium carbonate from seawater into their spicules. When these sponges die and their spicules settle on the seafloor, they contribute to calcium cycling in the ecosystem. This process can have implications for the overall carbonate chemistry of the ocean.

4. Sediment Stabilization: The presence of glass sponge reefs can help stabilize the seafloor by reducing sediment erosion and preventing sediment resuspension during underwater currents. This can have a positive impact on the surrounding environment by maintaining suitable conditions for other benthic (bottom-dwelling) organisms.

Glass sponges, with their filter-feeding behavior, habitat provision, and role in nutrient cycling, contribute to the overall health and functioning of marine ecosystems, particularly in deep-sea environments where they are commonly found. Conservation efforts to protect these unique and vulnerable organisms and their habitats are essential for maintaining the ecological balance of these ecosystems.

“To see how the reefs looked even 10 years ago. It is really sad to see the images we are witnessing when we go down there [now].”

Tori Preddy, Marine Life Sanctuaries Society

Why are Glass Sponge Reefs Still Under Threat?

Prior to the DFO protecting glass sponge reefs in BC waters, 50% of the reefs were damaged or destroyed by bottom trawling. However, despite the current protections in place, glass sponge reefs continue to be damaged by human activity. One cause of damage is the continued use of prawn and crab traps in these protected areas. Trappers who drop their traps right onto the reefs are destroying nine thousand years of nature’s work in a millisecond. Even if a dropped trap does not directly hit glass sponges, the sediment which is kicked up will suffocate them.

“We cannot enforce on destruction. That means that you can’t wait till someone drops a trap down there and hope that you’re going to give them a ticket or take away their gear. The reefs will be gone.”

Glen Dennison, Marine Life Sanctuaries Society

Glass sponges usually take over 200 years to grow only one meter in height. This means that every time they get damaged, they will also take hundreds of years to recover, if ever. Photo credit: Nate Slaco on Oceanographic

 “The DFO enforcement officers are doing the best job they possibly can out there. But they are so short-staffed that they just cannot protect the sound properly.”

Glen Dennison, Marine Life Sanctuaries Society

The fact that protected reefs are being damaged by illegal trapping indicates the DFO does not have the resources to properly monitor the protected areas. Moreover, while bottom-contact fishing is banned in these protected zones, anchor dropping is not, which means it is not illegal to drop an anchor and obliterate nine thousand years of nature’s work. The only way the glass sponge reefs on the Great Bear Coast will be properly protected is through the establishment of the Great Bear Sea Marine Protected Area Network, which will include vigilant monitoring through Coastal First Nations’ guardians and enhanced punishment for those callous enough to destroy these ancient wonders.



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