In the U.S., people eat more protein than they need to, which might not be bad for human health, but does pose a problem for the country’s waterways. The nation’s wastewater is loaded with the leftovers from protein digestion: nitrogen compounds (氮化合物) that can feed harmful algal blooms (藻华) and pollute the air and drinking water.

Maya Almaraz, a biogeochemist at the University of California, Davis, and her team wanted to see how much of this nitrogen entered into the U.S. wastewater system because of a protein-heavy diet. The researchers found that the majority of nitrogen pollution present in wastewater—some 67 to 100 percent—is a by-product of what people consume.

Once it enters the environment, the nitrogen can have a series of ecological impacts. It helps algae grow much faster than they would normally, which is harmful to humans, other animals and plants. And when the algae eventually die, the problem is not over. Microorganisms (微生物) that feed on dead algae use up oxygen in the water, leading to “dead zones”, where many species simply cannot survive, in rivers, lakes and oceans.

Although it is possible to treat algal blooms, many of the current methods are not always effective at getting rid of all of the harmful growth. Some of these methods can even lead to additional pollution. So the best strategy for dealing with the effects of nitrogen pollution is prevention, says Patricia Glibert, an ocean scientist at the University of Maryland. Almaraz and her team state that controlling nitrogen pollution could be approached more quickly with a change in eating habits that could save billions of dollars in the long term.

You've probably learned that bears eat a lot before hibernating (冬眠), putting on weight suddenly. It's an enviable practice, because those bears don't have the same health problems as fat people. A study published in Cell Reports has found that it might be due to the bear's friendly gut microbes (肠道细菌).

In summer, bears go through an extreme period of eating, while they eat nothing about six months during winter hibernation. To compare the microbiomes (微生物) of both seasons, the researchers collected the samples of their waste from 16 wild bears during hibernation and in summer. What they found is that the bear's lifestyle changes dramatically with seasons. During hibernation, the kinds of microbiomes became less than the summer samples.

To find out how that might affect metabolism (新陈代谢), the researchers transferred the microbes from the winter and the summer into lab mice. Mice with the summer microbes gained more weight than those with the winter microbes. However, those fatter summer mice weren't different from the winter mice in their glucose (葡萄糖) metabolism. “Thus, the bear may be atypical model for healthy obesity (肥胖) and studying hibernation might be a promising approach to developing new treatments for obesity,” the authors write.

However, there are still more researches needed before humans benefit from bear gut microbes. The researchers note that relying on free-ranging wild bears means they know little about their food intake and other habits. And though they were able to produce interesting metabolic results in mice, mice are quite different from humans. And another research suggests that exposure to cold can also change the composition of gut bacteria, improving glucose metabolism and fat burning abilities in mice.

Papastamatiou’s team studied gray reef sharks living in the waters off Palmyra Atoll, a sunken island ringed by reefs, in the central Pacific Ocean between the Hawaiian Islands and Fiji. They attached small location transmitters to 41 sharks, which allowed them to track the animals movements around the reef. After tracking the sharks for four years, the researchers found that the same groups of sharks frequently returned to the same parts of the reef over and over again. They also found that some of the groups stuck together longer than previous studies have observed.

The sharks might be motivated to stay together, Papastamatiou says, because it makes hunting for food easier, “If we hang out together and I see something, then you can come and try and take advantage of that,” he says. “And alternatively, if you see something, then I can try and take advantage of that.”

He emphasizes that the sharks don’t hunt together but says that as long as the group isn’t too large —which would raise competition and conflict—socializing appears to benefit the sharks. And that may be one of the factors that led to sociality in the species.

David Shiffman, who studies shark ecology and conservation at Arizona State University, says he was surprised to learn the sharks stuck together for so long. “I mean, I don’t have a lot of friends I do that with,” he jokes.

Sharks are amazing creatures, Shiffman says. In addition to knowing where to grab a bite by watching their friends, he says, some species of sharks can also learn to solve simple puzzles, just by watching other sharks solve them. Given their intelligence and social abilities, he says perhaps it’s time to drop prejudices about sharks. “It turns out that they are a lot smarter than other people think, and they have more complex social behaviors and more complex abilities to process their environment and learn and change,” Shiffman says.