Oceans Are Growing Darker—and Losing Life

Between 2003 and 2022, 21% of the global ocean darkened, affecting more than 75 million square kilometers. This phenomenon alters the optical properties of seawater and reduces the depth of photic zones—the sunlit layers that sustain 90% of all marine life and essential ecological processes.

More than 9% of the ocean experienced a reduction in photic depth of over 50 meters, while 2.6% lost more than 100 meters. These changes undermine the ocean’s ability to regulate climate and produce oxygen.

The causes include agricultural runoff, increased sediments and organic matter, shifts in plankton communities, algal blooms, and rising sea surface temperatures. Climate change acts as an amplifier of a real and persistent threat to marine life.