With the relatively recent breakup and collapse of the Larsen A ice shelf in the western Weddell Sea in Antarctica very large changes have occurred to to the communities of life living on the sea bed below. In particular, the area has been rapidly colonized by ‘slow-growing’ glass sponges (Hexactinellida) — much more rapidly than was even thought possible.
Newly released research from the Alfred Wegener Institute in Germany has documented these changes as they have occurred over the years of 2007-2011. Before the collapse in 1995 the region was completely covered by permanent ice and the life in the area was mostly composed of sea squirts — but we’re nearly completely displaced by other organisms with the collapse. The interesting part though is that glass sponges had previously been thought to be a form of life which lived very long and slow lives — some researchers have even estimated that they may even have natural lifetimes that last over 10,000 years.
“By comparing identical tracks video-surveyed by remotely operated underwater vehicle in one of the least accessible parts of the Antarctic, we found two- and three-fold increases in the biomass and abundance of glass sponges, respectively, from 2007 to 2011,” states Claudio Richter of the Alfred Wegener Institute in Germany. “This is much faster than any of us would have thought possible.”
“A general principle to be learned from our study is that benthic communities are very dynamic, even under the extreme environmental conditions prevailing in the Antarctic,” states the study’s lead author, Laura Fillinger. “Only four years ago, the study area was dominated by a species of sea squirt. Now this pioneer species has all but disappeared, giving way to a community dominated by young individuals of a glass sponge.”
The researchers are now planning to continue going to the same site regularly over the next few years to document further changes as they occur there. They think that the “seafloor there will ultimately reach a climax community that looks like those in other shallow and seasonally ice-covered Antarctic waters.” At this rate though, that climax community will arrive much more quickly than was previously thought to be possible — within decades, rather than centuries.
“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,” Richter continues. “Where cold, darkness and food shortages had previously reigned, sunlight now allows plankton growth in surface waters and, hence, a rain of food comes down to the sea bed.”
“Exactly what this will mean for the rest of the Antarctic or the planet is impossible to say. Glass sponges serve as important habitat for diverse communities of fish and invertebrates, but there is still a lot that no one really knows about them.”
As of now it’s really anyone’s guess. “If the alarming rate of ice shelf disintegration continues… glass sponges may find themselves on the winners’ side of climate change,” the researchers speculate.
The new findings were just published in the July 11th edition of the journal Current Biology.