On first impression, Antarctica may look barren and less biodiverse than most other places on Earth—and, even, simple in its black-and-whiteness. In reality, however, in recent years we’ve learned that the White Continent is overflowing with life; that is, if you include the microscopic kind.
In Antarctica, tiny mites, roundworms, snow fleas and springtails all wriggle around, invisible to the naked eye. They dominate terrestrial life in Antarctica. And much like the biodiversity that results from the footsteps of elephants in Africa, the larger fauna here—namely, elephant seals and penguins—are responsible for this lively abundance at the bottom of the world.
According to a recent study in the science journal Current Biology, excrement deposited by elephant seals and Adelie, chinstrap and gentoo penguins in Antarctica adds much needed nitrogen to the surrounding landscape, leading to a large uptick in arthropods (invertebrate animals—such as arachnids, crustaceans and insects—that have a segmented body and jointed appendages, a chitinous exoskeleton molted at intervals and a dorsal anterior brain) and nematodes (elongated, cylindrical worms parasitic in animals or plants, or free-living in soil or water). Of course, for any living thing in Antarctica, life is tough. But unlike the visiting birds and mammals, microscopic animals can’t venture into the nutrient-rich waters around the continent for a quick bite.
Luckily, elephant seals and penguins deliver “marine takeout” to these hardy invertebrates.
Visible from space
From hippos to whales, many animals around the world are known to benefit their ecosystems by their droppings, but most of these creatures “go” in environments that will support a lot of different kinds of life. Antarctica’s cold, dry climate isn’t all that amicable to biodiversity.
It’s also not exactly friendly to researchers. The continent’s dangerously cold temperatures, massive size and desolation make investigations difficult. Most of the science conducted there is limited to areas around research stations, and there aren’t many of those. That’s why one of the coauthors of the study, Stef Bokhorst, an ecologist at Vrije Universiteit in Amsterdam, decided to follow the nitrogen.
The poop of millions of penguins and seals in Antarctica is visible from space, allowing researchers to look for these areas in satellite imagery instead of engaging in costly field excursions. Once the animals’ colonies were located, the ecologists waded through piles of waste and used gas analyzers to measure the nitrogen levels. Because the element has several isotopes, they were able to track it as it moved through the environment from the penguin and elephant seal colonies to the lichens and mosses growing in the area, and then to the arthropods and nematodes in the soil.
The research team found that for the most part, the lichens and mosses were unaffected by the excrement but the microarthropods were. These animals were two to eight times more abundant in the regions tainted by elephant seal and penguin poop than in the regions that weren’t.
One of the most surprising findings was that this impact stretched far beyond the boundaries of the animals’ colonies. The nutrients didn’t just stay where the droppings landed. Penguins and seals feed on fish, krill and squid from the ocean. They come onto the coasts to breed, roost and defecate. Their excrement then evaporates as ammonia gas and subsequently gets blown farther inland, making its way into the soil and creating a “nitrogen footprint” of up to 240 times the size of a colony.
In fact, these expanded, fertilized areas had invertebrates that numbered in millions per square meter. By contrast, there are only about 50,000 to 100,000 invertebrates per square meter in the grasslands of Europe or the United States.
Using the data they collected and the locations of other penguin colonies the researchers couldn’t get close to, the scientists mapped out likely biodiversity hot spots across the Antarctic Peninsula. If their analysis is right, the peninsula is bursting with microscopic critters.
This study points out the important role marine vertebrates, such as penguins and elephant seals, play in their ecosystems—and what’s at risk if we lose them. Unfortunately, today some populations are facing serious dangers.
Seen from the perspective of a warmer future
As our climate warms, storms could become more common in Antarctica, threatening key habitats for large animals. An entire penguin colony still hasn’t recovered after a 2016 storm wiped out thousands of chicks and eggs.
And the Antarctic Peninsula, in particular, saw rapid warming in the late 1990s. If it continues, animals that rely on the ice to live and breed will become imperiled. Losing these big, charismatic species will cause the chain of biodiversity hot spots to unravel. The loss or move of a penguin colony would generate ripple effects throughout the ecosystem.
Locating these hot spots is becoming more and more pertinent. In 2019, the United Nations issued a report that found that 1 million of the world’s approximately 8 million species were doomed due to climate change and other human-caused problems, such as habitat loss and pollution.
While Antarctica’s vibrant invertebrate communities experience very low predation, the introduction of invasive plant species—particularly grasses—could change this. Seeds could be blown in from South Africa and South America or carried in by seabirds and the boots and other clothing of humans.
Those seeds could find a suitable home in Antarctica; for just as the penguin and seal colonies enrich the soil for native plants, it’s also possible that they are making it ideal for invasive species, as well, which could be hardier and provide shelter for predatory insects, such as beetles and spiders. While right now, the ecosystem can’t support any mammals, such as mice and rats, it’s possible that it could in the future. Scientists plan to study how invasive species might take advantage of this newly discovered scat situation and how conservationists might—hopefully—be able stop them in their tracks.
Viewed from a verity
We often tend to think of marine and terrestrial realms as being separate, but this research shows that penguins and seals act as a sort of “ocean-to-earth conveyor belt,” bringing nutrients from the sea onto land through their natural behavior.
In the past, most of the research on Antarctic biology focused on cold temperatures and water scarcity as the two limiting factors for supporting life. This study brings a third component—nutrient availability—into the picture. Nitrogen is scarce in Antarctica, so penguin and seal excrement contribute significantly to the ecosystem.
For me, this study makes clear that biodiversity isn’t just a matter of counting; for it’s found not only in the types and numbers of animals in a locality, but in how they interact with their environments. Biodiversity is intricately nuanced.
I’d argue that assessing the quantity of species is certainly important, but we can’t lose sight of the fundamental truth that life follows life.
Here’s to finding your true places and natural habitats,