Study Links Retreating Antarctic Ice Shelves to Rapid Expansion of Glass Sponges

A latest study published in the scientific journal Current Biology reveals the presence of a prolific community of glass sponges colonizing the freezing waters around Antarctica, which apparently came up after the collapse of the Larsen A ice shelf.

This finding astonished the scientific community as it believed that glass sponges have an extremely slow growth rate.

Following the breakup and collapse of the Larsen A ice shelf in the northwest part of Weddell Sea in 1995, a lot of fundamental changes have occurred in the life on the sea bed. Apparently, the disappearance of this ice shelf that was about 770 square miles (2,000 square kilometers), fueled the glass sponge invasion. This report was produced by biologists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research.

The new finding,  conducted by Claudio Richter along with AWI biologist Laura Fillinger and colleagues from the University of Gothenburg and the Senkenberg Research Institute and Natural History Museum, contradicts the previous assumption that these marine creatures are slow to grow as the scientists spotted sponges that were double in biomass and three times the number that was present between 2007-2011.

Looking at the increasing population of the glass sponges that supplanted competitors for food, the research team concluded that the 1995 collapse of the Larsen A ice shelf was directly associated with the growing number of glass sponges.

"We now know that glass sponges may undergo boom-and-bust cycles, allowing them to quickly colonize new habitats in a short period of time", said project leader Prof. Dr. Claudio Richter. "To the organisms living on the sea bed, the disappearance of the hundred-metre-thick Larsen A ice shelf must have been like the heavens opening up above them."

Glass sponges are also known as Hexactinellida and dominate the shallow seafloor in the Antarctic. These survive by feeding on the tiniest planktons that they consume after filtering from water. They make their own habitat. They hide in their vase like bodies. They grow so slowly that scientists believed that to reach at least 2 meters they might take 10,000 years or more, but these assumptions are now being challenged.

Whenever ice shelves break there is new space provided for the underwater world.  This latest find has left the scientific community wondering whether glass sponges are benefiting from global warming.

The study was based on the data gathered during the 2011 Polarstern expedition that was done using a remotely operated vehicle. The vehicle was placed at a depth of 140 meters onto the sea bed. They then compared these observations with an earlier expedition undertaken in 2007 with Polarstern during which they observed large sea squirts and a few glass sponges. Four years later they observed that sea squirts were replaced by three times the number of  glass sponges and some juveniles, reports Science Recorder.  

"There are still too many unknowns to make predictions.  One example is the question of the influence of competitors: currently we are witnessing a fierce competition for space on the sea bed.  Another concern is predators: in our dive in 2011 we hardly saw any of the snails and starfish, which feed on glass sponges.  However, it is possible that these voracious predators will follow suit and wreak havoc," cautions Laura Fillinger.