Antarctic Food Chain Mystery (03:51)
An icebreaker takes scientists on a mission to find out what is destroying the krill population. The continent is home to millions of penguins, seals, and whales dependent on the shrimp-like creatures; penguins are also declining.
Role of Krill (04:01)
Scientists on Adelaide Island monitor wildlife. Krill connect top predators with phytoplankton at the food chain base. Algae are productive in summer and die off in winter. Krill are spawned in summer, but larvae must live through winter.
Expedition Day 1 (04:04)
Led by Bettina Meyer, 50 scientists board the icebreaker Polarstern to find Antarctic krill larvae and observe their winter behavior. During the first leg, they will deploy a rectangular mid-water trawl net to find krill; learn about krill anatomy.
Krill Decline (03:09)
Trawling enables scientists to survey marine life directly. Biological oceanographers Brian Hunt, Evgeny Pakhomov, and Angus Atkinson combined results from thousands of historical trawls to discover the krill population declining. The Polarstern heads due south to investigate why.
Marginal Ice Zone (04:05)
The Polarstern enters a region featuring hidden icebergs. The Southern Ocean freezes over every winter, more than doubling in surface area. Atkinson and Pakhomov found a link between annual variations and krill population, suggesting that krill somehow depend on the ice.
Locating a Stable Ice Floe (04:32)
The Polarstern is designed to crack pack ice. Scientists will dive beneath the ice to look for krill and film their behavior. They fly a helicopter with a remote sensor to find a suitable dive site.
Preparing to Dive (04:13)
Scientists set up a dome tent providing shelter for diving beneath the Antarctic ice. Divers express anticipation and nervousness about their mission. Team leader Ulrich Freier enters the water.
Beneath Antarctic Ice (03:00)
The landscape variability and presence of life fascinates the divers. They find little phytoplankton—raising the question of what krill larvae are feeding on.
Krill in an Antarctic Environment (03:28)
Marine biologists discover krill larvae feeding on something on the underside of the ice. Divers take samples.
Antarctic Phytoplankton (02:53)
Krill larvae feeding on algae frozen to the underside of ice floes grow at a normal rate. Climate change is reducing their food source.
Antarctic Warming (03:44)
The Sheldon Glacier has receded by two miles in 20 years. Climate change causes ice to freeze later and melt earlier. Later freezing means fewer phytoplankton are incorporated into ice and less food for krill larvae.
Krill Feeding Patterns (04:03)
Polarstern scientists dive in a second location to investigate krill behavior. The creatures feed on algae on the underside of ice floes during the day, and feed in the open water at night.
Krill Circadian Rhythms (05:15)
Light exposure and day length, rather than temperature, dictates krill feeding patterns and seasonal behavior—making it difficult for the species to adapt to climate change. Polarstern scientists make a final dive to observe krill in the marginal ice zone.
Credits: Mystery Beneath the Ice (00:51)
Credits: Mystery Beneath the Ice
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