The Key to Biodiversity in Antarctica Is Penguin Poop
A new study shows nitrogen from penguin and elephant seal dung powers a diversity of arthropods and nematodes in surrounding areas
With Antarctica’s freezing temperatures and desert-like precipitation levels, it may seem like an unlikely candidate for biodiversity. But a new study shows that some parts of the frozen continent host much more life than others: it turns out that areas near penguin and elephant seal colonies have entire food webs powered by poop.
According to a new study in the journal Current Biology, the excrement deposited by gentoo, Adelie and chinstrap penguins as well as elephant seal colonies on the Antarctic Peninsula adds much needed nitrogen to the surrounding landscape, leading to a large uptick in insects like springtails and mites.
Karen Weintraub at The New York Times reports that because of its harsh conditions, researchers have a difficult time studying biodiversity on the polar continent. That’s one reason co-author Stef Bokhorst, an ecologist at Vrije Universiteit in Amsterdam, decided to try and follow the nitrogen. That meant wading through piles of animal waste, and lugging gas analyzers into the field to measure nitrogen levels. Because the element has several isotopes, they were able to track it as it moved through the environment from the penguin colonies to the moss and lichen growing in the area and then to insects and nematodes in the soil.
The impact of the penguin and seal colonies extends much farther than the boundaries of their breeding grounds. In some cases the nitrogen footprint of the animals was 240 times the size of their colony. The biggest impact was in the soil where they counted millions of invertebrates per square meter, compared to just 50,000 to 100,000 found in soils in Europe and North America where it’s believed predators and other factors keep the populations in check.
Antarctica, it turns out, is the perfect place to study how nutrients interact with ecosystems. That’s because the food webs in Antarctica are stripped down compared to tropical forests or temperate grasslands, where densely intertwined interactions between animals, plants, diseases, soils, waterways and other factors complicate things. In Antarctica, it’s just one relatively simple circle of life that begins at the penguin’s cloaca, the bird’s all-purpose outlet that leads to its intestinal, urinary and genital tracts.
Much of the benefit doesn’t come directly from the poop itself, but from its byproducts. “What we see is that the poo produced by seals and penguins partly evaporates as ammonia,” Bokhorst tells Agence-France Presse. “Then, the ammonia gets picked up by the wind and is blown inland, and this makes its way into the soil and provides the nitrogen that primary producers need in order to survive in this landscape."
Pacifica Sommers, an ecologist at the University of Colorado Boulder, not involved in the study, tells Mary Beth Griggs at The Verge that the penguins and seals allow the bounty of the surrounding Southern Ocean to power biodiversity on land.
“They essentially deliver those nutrients from the ocean where they harvest them, onto land where they poop them out,” Sommers tells Griggs. “A little bit of poop goes a long way. And a lot of poop, as this paper found, goes a lot further.”
The study allowed the researchers to use penguin and seal colonies as proxies for biodiversity, allowing them to create some of the first maps of biodiversity hotspots on the continent. Bokhurst says the maps are a first step in monitoring biodiversity in Antarctica and will be updated with satellite data as penguin and seal colonies move over time.
But Weintraub reports that, though the impact of climate change on these simplified ecosystems has not been studied, they are under threat. Bokhurst is currently studying how invasive species, in particular grasses, brought to the continent on the boots of tourists hoping to get a glimpse of the pooping penguins could be changing the habitat.