--- title: "Antarctic Glass Sponges: Boom-and-Bust Giants Under the Ice" url: https://thesea.org/antarctic-glass-sponges/ date: 2026-11-13 modified: 2026-11-13 lang: en author: "Blane Perun" description: "Antarctic glass sponges: the slow-growing giants of the Ross Sea and the Antarctic shelf, including the giant volcano sponge, their sudden booms after decades of stillness, and their rapid spread after the Larsen A ice shelf collapsed." categories: - "Sponges" word_count: 1847 --- # Antarctic Glass Sponges: Boom-and-Bust Giants Under the Ice [TheSea.Org](/)▸[Sponges](/sponges/)▸Antarctic glass sponges # Antarctic Glass Sponges — Boom-and-Bust Giants Under the Ice Sponges By [Blane Perun](/about-blane-perun/) November 13, 2026 10 min read What are Antarctic glass sponges? Antarctic glass sponges are hexactinellid sponges, with skeletons of silica, that form dense “sponge grounds” on the continental shelf around Antarctica. They include giants such as the volcano sponge *Anoxycalyx joubini*, which can reach about 2 metres and is thought to live for centuries or more. Long assumed to grow almost imperceptibly, they surprised scientists by showing sudden **booms** of recruitment and growth, for example after the **Larsen A ice shelf** collapsed in 1995, followed in some places by die-offs. Quick facts ClassHexactinellida (glass sponges) SkeletonSix-rayed silica spicules Giant species*Anoxycalyx joubini*, up to about 2 m Common genus*Rossella* Water temperatureAround −1.8 °C on much of the shelf Key eventRapid spread after Larsen A ice shelf collapse (1995) Most people picture Antarctica as a world of ice, penguins and whales. Beneath the sea ice, on the shelf around the continent, lies something few people ever see: forests of glass. Glass sponges, some as tall as a person and possibly older than most human civilisations, cover large areas of the seafloor, creating habitats for fish, sea stars and countless invertebrates. For decades scientists thought these sponges were the ultimate slow-motion animals, growing so slowly that change could barely be measured. Then they started to boom. I have never dived in Antarctica, and these sponges live mostly well beyond recreational diving depths, so this page is written from the research rather than from experience. But as someone who has spent decades watching sponges on tropical reefs and in my own tanks, the Antarctic story is one of the most surprising sponge discoveries of recent years. What makes a glass sponge? Glass sponges, class Hexactinellida, have skeletons built from silica, the same material as glass. Their spicules are typically six-rayed, and in many species they fuse into rigid lattices that remain standing long after the sponge dies. Unlike most other sponges, much of a glass sponge’s body is made of syncytial tissue, a continuous web of cytoplasm with many nuclei rather than separate cells, which lets them conduct electrical signals and stop their pumping very quickly when disturbed. Glass sponges are mostly deep-sea animals worldwide, found below a few hundred metres. Antarctica is unusual because cold, silica-rich water lets them live on the continental shelf at much shallower depths, in places within reach of scientific divers. Our page on [glass sponges](/glass-sea-sponge/) covers the group in general, and the [Venus flower basket](/venus-flower-basket/) is their most famous tropical relative. The sponge grounds of the Antarctic shelf In many parts of the Antarctic shelf, glass sponges dominate the seafloor, forming some of the densest sponge communities on Earth. The shelf seafloor is cold, stable and, beneath the sea ice, relatively dark. Rich plankton blooms in the short summer, driven by diatoms and other algae, send food down to the bottom. Under those conditions, glass sponges of the family Rossellidae, including several *Rossella* species and the giant volcano sponge *Anoxycalyx joubini*, form dense stands on muddy and rocky bottoms. Around them, spicules from dead sponges build up into thick mats that change the seafloor itself, creating a habitat where other animals settle. Fish lay eggs in and among the sponges, brittle stars and crustaceans live inside their cavities, and sea stars and sea slugs graze on them. In the Ross Sea and McMurdo Sound, where scientists have studied them for decades, sponges and their associated animals make up a large share of seafloor life. Anoxycalyx joubini: the giant volcano sponge The most impressive Antarctic glass sponge is *Anoxycalyx joubini*, sometimes called the giant volcano sponge for its shape. It grows as a large barrel or volcano-shaped form that can reach about 2 metres tall, making it one of the largest sponges in the world. For many years scientists believed it grew incredibly slowly, and estimates based on growth measurements and metabolic rates suggested that the biggest individuals could be many centuries to thousands of years old; some calculations have put the oldest at more than 10,000 years, though such figures are highly uncertain. Whatever the exact ages, these are some of the longest-lived animals known. Our pages on [deep sea sponge lifespan](/deep-sea-sponge-lifespan/) and [giant sea sponges](/giant-sea-sponge/) put those claims in context. The McMurdo surprise: decades of stillness, then a boom The best long-term record comes from McMurdo Sound, where American researchers began monitoring sponges in the late 1960s. In experiments started in 1967, scientists led by Paul Dayton placed artificial structures on the seafloor and tagged sponges to measure growth and recruitment. For decades almost nothing happened. Many large sponges barely grew, and very few young sponges settled on the experimental structures. That fitted the idea of glass sponges as slow, stable, unchanging communities. Then, when the team returned and surveyed the sites again in later years, they found that young *Anoxycalyx joubini* had settled and grown rapidly on some of the old structures, reaching sizes that would previously have been thought to take centuries. A study published in 2013 described this unexpected recruitment and growth, and noted that some large sponges had also died. The researchers linked the changes to shifts in sea ice and plankton supply, suggesting that these sponges respond in bursts to rare good conditions, with long quiet periods in between. After Larsen A: life where the ice shelf used to be An even more dramatic boom followed the collapse of an Antarctic ice shelf. In 1995 the Larsen A ice shelf, on the eastern side of the Antarctic Peninsula, disintegrated, and in 2002 the larger Larsen B shelf to its south followed, exposing seafloor that had been covered by floating ice for thousands of years. When scientists aboard the German research ship *Polarstern* surveyed the former Larsen A area in 2007 and again in 2011, they found that glass sponge communities had changed remarkably fast. A study published in 2013 reported that the biomass of glass sponges, dominated by young *Rossella*, had roughly tripled between the two surveys, a pace no one expected from supposedly slow-growing animals. With the ice gone, plankton blooms could reach the seafloor, and the sponges responded quickly. The lesson from both McMurdo and Larsen A is that Antarctic glass sponge communities are not frozen in time. They can lie dormant for decades and then expand rapidly when food supply changes, and they can also die back. That makes them both resilient and vulnerable to climate change. | Species or group | Shape | Size | Notes | | ---------------- | ----- | ---- | ----- | | *Anoxycalyx joubini* | Barrel or volcano | Up to about 2 m | Among the largest sponges; ages possibly many centuries | | *Rossella* species | Vase, sac or barrel | Up to tens of cm | Dominated the post-Larsen A boom | | Spicule mats | Seafloor layer | Can be thick | Built from dead sponges; habitat for other animals | How scientists study sponges under the ice Studying animals that live beneath sea ice in water below freezing is hard, and much of what we know comes from a small number of determined research teams. At McMurdo Station, scientific divers work through holes drilled or melted in the sea ice, diving in water around −1.8 °C with drysuits and heavy undergarments, and can reach sponge stands on the shallower parts of the shelf. Their great advantage is the clarity of the water under the ice in early spring, which can be extraordinary because there is so little plankton before the summer bloom. Deeper sponge grounds are studied from ships with towed cameras, remotely operated vehicles, grabs and trawls, and from long-term photographic transects that are revisited over years. Measuring the growth of an animal that may change very little in a decade requires patience: tagging individual sponges, photographing them against scale bars, and returning to the same spot years later. The value of these long records is obvious from the McMurdo story. If the monitoring had stopped after twenty years, scientists would have concluded that Antarctic glass sponges never change. Only by coming back decades later did they discover the booms and die-offs. I recognise something similar from running reef systems for many years: some of the most important changes in a tank show up only over long periods, and the logbook matters as much as any single test. Researchers have also been intrigued by the spicules themselves. Some Antarctic glass sponges have long spicules that conduct light, and it has been suggested that they may channel light to symbiotic algae inside the sponge, though that idea remains under study. Threats and protection Antarctic glass sponges face natural and human pressures. In shallow water, icebergs scraping along the seafloor and anchor ice forming on the bottom can destroy sponges. Changes in sea ice alter plankton supply, which, as McMurdo and Larsen A show, can drive both booms and die-offs. Warming and ocean acidification may affect them over the long term, although silica skeletons are less vulnerable to acidification than calcium carbonate ones. Bottom fishing is a threat elsewhere in the world, and the Antarctic’s remoteness and international regulation have so far protected most sponge grounds. In 2016 the countries of the Commission for the Conservation of Antarctic Marine Living Resources agreed the Ross Sea region marine protected area, one of the largest in the world, which includes extensive sponge habitats. For the wider ecosystem, see our pages on the [Southern Ocean](/southern-ocean/) and [krill](/krill/). Frequently asked questions Are there glass sponges in Antarctica? Yes. Glass sponges form dense communities on the Antarctic continental shelf, often at shallower depths than elsewhere in the world. What is the largest Antarctic sponge? *Anoxycalyx joubini*, the giant volcano sponge, which can reach about 2 metres tall. How old are Antarctic glass sponges? The largest are thought to be centuries old or more. Some estimates exceed 10,000 years but are highly uncertain. What happened to sponges after the Larsen A ice shelf collapsed? Surveys in 2007 and 2011 found glass sponge biomass in the area had roughly tripled, mostly young *Rossella*, as food from plankton blooms reached the seafloor. Why can glass sponges live in shallow Antarctic water? Cold, silica-rich water and stable conditions on the shelf suit them, conditions found elsewhere mainly in the deep sea. What eats Antarctic sponges? Sea stars and sea slugs graze on them, and many other animals live on or inside them. Sources & further reading - Fillinger, L. et al. (2013). Rapid glass sponge expansion after climate-induced Antarctic ice shelf collapse. *Current Biology* 23: 1330–1334. - Dayton, P. K. et al. (2013). Recruitment, growth and mortality of an Antarctic hexactinellid sponge, *Anoxycalyx joubini*. *PLoS ONE* 8(2): e56939. - Gatti, S. (2002). The role of sponges in high-Antarctic carbon and silicon cycling. *Berichte zur Polar- und Meeresforschung* 434. - CCAMLR, Ross Sea region marine protected area (2016). Continue reading More from Sponges [SpongesGlass SpongesDeep-sea animals with skeletons of silica. ](/glass-sea-sponge/) [SpongesDeep Sea Sponge LifespanThe 11,000-year-old glass sponge. ](/deep-sea-sponge-lifespan/) [Section hubSpongesEvery sponge article on TheSea.Org. ](/sponges/) BP Last updated November 13, 2026 Written by Blane Perun Blane Perun has been exploring Earth’s oceans and marine life for over 25 years. Founder of TheSea.Org in 1999, underwater photographer, coral aquaculture pioneer, and explorer of 80+ countries. [About Blane Perun →](/about-blane-perun/) [More on Sponges →](/sponges/)