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Glass sponges in the West Weddell Sea.

Glass sponges found in Antarctica may grow faster than scientists once thought.

Photograph courtesy Tomas Lundalv, Alfred Wegener Institute

Jane J. Lee

National Geographic

Published July 11, 2013

Conventional wisdom holds that life in Antarctica moves at a glacial pace. Marine creatures called sponges, which live on the seafloor, have been known to go a decade without any measurable growth in the Antarctic. But that thinking has changed, in part because of a startling discovery off the eastern coast of the Antarctic Peninsula.

Researchers have found a "boomtown" of sponges. In a study published July 11 in the journal Current Biology, they report on the explosion of a community of glass sponges—organisms with skeletons made of silica, a mineral component of glass—on the seafloor below where an enormous ice shelf used to be.

These sponges—filter feeders not known for their rapid development—doubled in biomass and tripled in number over the course of two growing seasons.

Everyone believed that glass sponges in this area wouldn't grow and expand so rapidly, said Claudio Richter, a marine biologist at the Alfred-Wegener Institute in Bremerhaven, Germany, and a study co-author.

Antarctic sponges are famous for being the slowest of the slow-growing, said David Barnes, a benthic ecologist with the British Antarctic Survey in Cambridge who was not involved in the project.

"Now you've got these guys who [are] growing at the rate of tropical sponges," he said. No one thought those rates of change happened in the Antarctic.

Scientists are eager to solve the mystery—not just because they want a better understanding of sponge ecology in the Antarctic, but also because these seafloor animals have the potential to store carbon. This could be a boon when it comes to figuring out ways to address climate change.

Here Comes the Sun

This startling population boom is partly due to the collapse of the Larsen A ice shelf in 1995, Richter and colleagues write. In late January of that year, an area about 770 square miles (2,000 square kilometers) disintegrated. (Related: "Ice Shelf Collapses Reveal New Species, Ecosystem Changes.")

Remnants of the ice shelf covered the area until January 2006, when they too collapsed. (Explore an interactive map of Antarctica.)

Areas once enclosed in darkness were bathed in sunlight for part of the year, boosting the growth of microscopic algae—the base of the marine food chain.

Researchers went down to the area in 2007 to see what was happening to the animals living on the benthos, or seabed. Thanks to cooperative sea ice and weather conditions, they were able to go back in 2011 to see how things had changed.

Richter and colleagues took video of these glass sponge communities with a remotely operated vehicle and collected samples using a trawl net.

Growing Mystery

But experts are at a loss to explain exactly why these glass sponge populations grew so quickly.

"That is the million-dollar question," wrote Paul Dayton, a marine ecologist at the Scripps Institute of Oceanography in San Diego, California, who was not involved in the study, in an email.

Dayton has seen rapid growth in Antarctic sponges before in McMurdo Sound, but the circumstances were different. He speculates that a large iceberg blocked production of larger species of plant plankton, allowing smaller species—the favored food of glass sponges—to grow. The sponges took advantage and grew rapidly. (Watch a live feed of McMurdo Station.)

Richter and colleagues speculate that algae blooms injected pulses of food into the benthic community, contributing to the growth of glass sponges near the Antarctic Peninsula, Dayton noted. That wasn't the case in McMurdo Sound when Dayton did his glass sponge study.

The answer probably lies in figuring out exactly which species of plant plankton the different glass sponge species need, he said.

Study co-author Richter speculates that there may have been some unknown factor that previously limited the sponges' growth, and somehow that factor may have been eliminated.

The British Antarctic Survey's Barnes also warns that this is just a snapshot of a dynamic seafloor community in a specific area. Once things settle down, the area could resemble a "normal" Antarctic benthic habitat.

A Sinking Feeling

Whatever the reasons for this boom in glass sponges, "the repercussions of all this are quite far-reaching," Barnes noted.

When plant plankton produce food, they take carbon out of the seawater, he said. And when glass sponges feed on that plankton, the carbon contained in their prey becomes locked away on the seafloor. When the sponges die, they're buried in the sediment, sequestering their carbon.

"This is a brand-new carbon sink, really," Barnes said.

And although, in the grand scheme of planetary carbon budgets, a patch of seafloor in the Southern Ocean isn't going to make a huge dent, it could affect the models researchers develop to study Earth's climate, he added.

Richter plans to delve into this boomtown mystery with his graduate students. Not much is known about the ecology of these sponges, so he plans to figure out what exactly the sponges are eating and how much energy they expend in their daily lives.

Follow Jane J. Lee on Twitter.

1 comments
Babu Ranganathan
Babu Ranganathan

NOT MADE BY NATURE! Just because something exists in nature doesn't mean it was invented or made by Nature. If all the chemicals necessary to make a cell were left to themselves, "Mother Nature" would have no ability to re-organize them into a cell. It takes an already existing cell to bring about another cell. The cell exists and reproduces in nature but Nature didn't invent or design it! Nature didn't originate the cell or any form of life.

Natural laws can explain how an airplane or living cell works, but it's irrational to believe that mere undirected natural laws can bring about an airplane or a cell. Once you have a complete and living cell then the genetic program and biological machinery exist to direct the formation of more cells, but how could the cell have originated naturally when no directing code and mechanisms existed in nature? All of the founders of modern science believed in God. Read my Internet article: HOW FORENSIC SCIENCE REFUTES ATHEISM 

Only evolution within "kinds" is genetically possible (i.e. varieties of dogs, cats, etc.), but not evolution across "kinds" (i.e. from sea sponge to human). How did species survive if their vital tissues, organs, reproductive systems were still evolving? Survival of the fittest would actually have prevented evolution across kinds! Read my Internet article: WAR AMONG EVOLUTIONISTS! (2nd Edition). I discuss: Punctuated Equilibria, "Junk DNA," genetics, mutations, natural selection, fossils, genetic and biological similarities between species.
 
Natural selection doesn't produce biological traits or variations. It can only "select" from biological variations that are possible and which have survival value. The real issue is what biological variations are possible, not natural selection. Only limited evolution, variations of already existing genes and traits are possible. Nature is mindless and has no ability to design and program entirely new genes for entirely new traits.

Visit my newest Internet site: THE SCIENCE SUPPORTING CREATION

Sincerely,
Babu G. Ranganathan*
(B.A. theology/biology)

Author of popular Internet article, TRADITIONAL DOCTRINE OF HELL EVOLVED FROM GREEK ROOTS

* I have had the privilege of being recognized in the 24th edition of Marquis "Who's Who In The East" for my writings on religion and science, and I have given successful lectures (with question and answer time afterwards) defending creation from science before evolutionist science faculty and students at various colleges and universities.

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