More than 90% of all ocean life lives in its shallowest, brightest places. Those places are shrinking, a new study shows. Sunlight that super tiny marine creatures like plankton can use for photosynthesis pierces the topmost 200 meters of the ocean surface. Plankton are nutrient-rich creatures. And the light allows them to thrive. In turn, this allows all other plants and animals in the food chain above them to survive. Less light means less plankton. And this threatens to topple marine biomes. "There has been research showing how the surface of the ocean has changed color over the last 20 years," Thomas Davies, a study author, said in a statement. Davies said this is perhaps because of changes in plankton numbers. Davies added that the results provide evidence that such changes cause widespread darkening. In turn, Davies said, this lessens the amount of ocean available for creatures that rely on the sun and the moon to live and reproduce. The journal Global Change Biology published Davies’ study. Davies teaches at the University of Plymouth. Davies is a marine conservation professor. The ocean’s light-suffused region is known as the photic zone. Davies’ team studied it using satellite data and ocean modeling software. They found that the darkening of the photic zone has affected over 20% of the ocean’s surface in the past 20 years. What's to blame? Warming waters that spur light-hungry algae blooms is one factor. Shifting currents that dredge more sun-blocking silt into the ocean’s upper waters is a second. In some places, the photic zone has shrunk by over 50 meters. That, Davies argues, warrants the world’s attention. People rely on the ocean and photic zones for air to breathe, fish to eat, to fight climate change, and for the planet's health, Davies said. Reflect: What do you think people could do to help protect important places where animals and plants live in nature? Photo of the ocean from Unsplash courtesy of Ryunosuke Kikuno.
