Antarctica remained largely untouched by humans for thousands of years, allowing an ecosystem to develop independently. However, since the 1990s, the last wild land on the planet is becoming an increasingly popular destination for adventure-seeking tourists. Now, a study newly conducted shows the visitors may be leaving behind harmful bacteria which could destroy that area’s bird population.

We mainly hear about zoonoses（动物传染病）— diseases like Ebola and pig flu — that are spread from animals to humans, yet humans can also infect animals with illnesses such as the flu. Researchers, however, believed that Antarctic animals, which had no recorded reverse（反向的）cases of zoonoses, were not affected by the danger due to the extreme environment. But microbiologists Marta Cerda-Cuellar at the Research Center for Animal Health, was not convinced this was true.

So she and some colleagues decided to examine waste samples from Antarctic birds for evidence of human bacteria. To ensure the waste was not polluted, the scientists had to collect it from the birds themselves. This was no easy task. It took the scientists four years to collect waste samples of 666 adult birds from 24 local species. However, it was well worth the effort. The results of their study showed the presence of several types of human bacteria in the bird waste.

“The bacteria, which are a common cause for infections in humans, don’t usually cause death in wild animals,” says Cerda-Cuellar. “However, the pathogens（病原体）that arrive to highly sensitive populations could cause extinction of some populations and destroy the local ecosystem.” The researcher also fears the presence of these bacteria could foresee the arrival of other, more deadly, pathogens as the number of people visiting the area increases. While the best solution would be to prevent tourism, Cerda-Cuellar, who believes it is because of efforts from tourist and scientific groups that Antarctica remains largely protected, says that’s impossible. “While we should do as much as possible to reduce the spread, it’s hard to believe we’ll stop tourism and science at these sites, and so it is hard to believe that humans won’t continue to pass on pathogens.”

As Mark Meekan, a tropical fish biologist at the Australian Institute of Marine Science in Perth, spotted a giant shadowy figure moving in the Indian Ocean, he was diving to take samples of a whale shark’s skin.

The sharks, averaging around 12 meters long, spend most of their lives in the deep ocean where they are hard to observe, so analyzing the chemical makeup of their tissues can help scientists learn more about their biology and behavior, including what they eat.

The skin samples that Meekan collected reveal that whale sharks, long thought to be strict meat eaters, also eat and digest algae (海藻). The findings add to evidence that whale sharks intentionally eat plants, potentially making them the largest omnivores on Earth.

Although algae has turned up in the stomachs of beached whale sharks before, “everyone thought it was just accidental ingestion (摄取),” Meekan says.

To find out if that assumption held up, Meekan’s team took tissue samples from 17 whale sharks feeding off the coast of Western Australia from 2015 to 2017. Whale sharks’ skin was rich in arachidonic acid (花生四烯酸) that is found in brown algae, the analysis showed.

The new work supports previous research by a different group that found algae-related nutrients in the skin of whale sharks near Japan. Together, the findings suggest that digesting greens is common practice for whale sharks.

But that doesn’t mean whale sharks are true omnivores, says shark biologist Robert Hueter. “This is a bit like saying that cows are omnivores because they eat insects while feeding on grass.”

Meekan admits that he isn’t sure whether whale sharks seek out algae, but the amount they eat isn’t incidental (附带的). “Their tissues hold a remarkable record of what they’ve been up to,” he says. “We’re now learning how to read this library.”