Oceans cover more than two-thirds of the surface of the planet - yet they are still not fully understood.
The world's oceans play an important role in the Earth's climate system, and millions of people depend on them directly for sustenance. People also traverse the oceans, and use them to transport goods. Yet the world's oceans are in trouble, as warming and acidification take their toll. They've also become a garbage dump for the planet, with consequences for marine life.
More than 5,500 teenagers collected trash from German rivers, took water samples, documented their findings — and analyzed the data with scientists. The results are alarming, says teacher and scientist Katrin Kruse.
Much of the CO2 we emit through the burning of fossil fuels ends up in the ocean, making the water more acidic. Because ocean acidification happens particularly fast in cold water, that spells trouble for cold-water corals. How do they cope as their environment becomes warmer and more acidic?