Glass Sponges and Some Possible Effects of Climate Change

Glass sponges are interesting animals that may be heading for trouble. They were thought to have become extinct millions of years ago but were discovered in British Columbia in the 1980s. In the laboratory, researchers at the University of British Columbia have found that the increased ocean temperature and acidity that are predicted to soon occur may harm the sponges. According to a UBC news report, the strength of the animals’ skeleton and their ability to obtain food were “drastically” reduced in the experiment.

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Staurocalyptus is a type of glass sponge. (Photo by NOAA/Monterey Bay Aquarium Research Institute, public domain license)

The Nature of Sponges

Sponges are animals, even though they lack organs. They belong to the phylum Porifera and bears pores called ostia on their surface. Water and its contents enter the sponge through the ostia. Inside the animal’s body, nutrients are removed from the water and waste added. The water then enters the central cavity of the sponge and leaves through an opening at the top called the osculum.

The current of water through the sponge is maintained by flagellated cells called choanocytes (or collar cells). These cells line the central canal. The flagellum of each cell beats to create the current leading to the osculum.

A basic illustration of sponge anatomy is shown below. The interior anatomy (and the physiology) are more complex than indicated, but the picture gives a useful overview of the situation. Though most sponges operate according to the system described above, scientists have discovered some fascinating carnivorous sponges that eat animals. Nature often has surprises for us.

Choanoflagellate_and_choanocyte

Sponge choanocytes resemble single-celled creatures called choanoflagellates. (Illustration by Open Stax, CC BY 4.0 License_

What Are Glass Sponges?

Glass sponges belong to the class Hexactinellida within the phylum Porifera. Their bodies contain spicules made of silica. Spicules are thin, needle-like structures that have a glassy texture. In some glass sponges, the spicules are joined together to form a lattice. The lattice is often referred to as a skeleton. This “skeleton”  provides support for the softer parts of the body.  It sometimes remains when a sponge dies and its soft tissues decay.

Glass sponges feed by filter feeding. Plankton (small, non-swimming or weakly swimming organisms in the water) and bacteria enter the sponge and are absorbed by its cells.  Wastes created by cell activity are released through the osculum.

Aphrocallistes_vastus (2)

Aphrocallistes vastus or the cloud sponge (Photo by Dan Hershman, CC BY 2.0 License)

Discovery of Glass Sponges in British Columbia

Until quite recently, glass sponges were thought to have become extinct around forty million years ago. In 1986 (according to the UBC report in the “References” section below) or 1987 (according to the NOAA report), glass sponges were discovered off the coast of British Columbia. After this exciting event, they were found in other areas. What seems to be unique to the Pacific Northwest region of North America is the existence of reefs created by the sponges. The animals have been called “living dinosaurs”.

The reefs have been found off the coast of the province, in the Strait of Georgia that separates Vancouver Island from the mainland, and in the Salish Sea between British Columbia and  the state of Washington. They don’t stretch a long distance from one location to another, but they are important structures where they do occur. They can be damaged by trawling and by sediments that enter the cavity of the sponge. The Government of Canada has created marine conservation areas in which commercial fishing is limited in order to protect the reefs.

In the northern part of the province, the reefs have been found at a depth of 90 to 300 metres. In the southern part,  they have been found at a depth of 22 metres as well as in deeper water.

The reefs are important for multiple reasons. They provide a suitable habitat for multiple organisms, including fish and invertebrates such as crabs and prawns. In addition, the living corals in the reef remove bacteria from the water and recycle nutrients.

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Euplectella aspergillum (Venus flower basket) with a brown squat lobster (NOAA Okeanos Explorer Program, Gulf of Mexico 2012 Expedition, public domain license)

Their sheer size and tremendous filtration capacity put them at the heart of a lush and productive underwater system, so we wanted to examine how climate change might impact their survival. (Quote from Angela Stevenson, UBC, with respect to glass sponges)

Potential Effects of Climate Change

The species used in the UBC experiment was Aphrocallistes vastus, or the cloud sponge. One place where it’s found is Howe Sound, which is connected to the Strait of Georgia. At the start of the experiment, the lead researcher tried to keep the sponges in conditions that were as natural as possible. She then placed the animals in water with increased temperature and acidity that matched the values predicted to soon occur in the ocean.

After one month in the new environment, the sponges had a fifty percent lower pumping ability. The ability to pump water out of the sponge started to decrease just two weeks after the environmental change. The sponges also had tissue loss of 10 to 25 percent and became weaker. Researchers say that weakened sponges would be more likely to be injured by marine animals moving among them. It’s also possible that the reef could be damaged.

If we don’t do our best to stand up for them, it will be like discovering a herd of dinosaurs and then immediately dropping dynamite on them.”  (Quote from Angela Stevenson, UBC, with respect to glass sponges)

Of course, the future is uncertain. We can’t be sure about future conditions in the ocean.  Based on regular records of Howe Sound conditions since 2016, however, researchers suspect that it won’t be long before the environmental conditions used in the experiment become a reality.  Glass sponge reefs help to protect the health of the ecosystem. It would be a shame to lose the animals after discovering them.

References

  • Introduction to glass sponges from NOAA
  • Climate change an imminent threat to “living dinosaurs” from the University of British Columbia
  • Warming waters could put rare, fragile glass sponge reefs at risk from the CBC (Canadian Broadcasting Corporation)

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