Ocean Darkening is Causing Marine Habitats to Shrink
Just below the ocean’s surface, the sun’s rays break to illuminate seemingly infinite deep blue— here, sunlight powers life. By around 200 metres down, the very last drops of sunlight vanish — this region, known as the photic zone, is home to 90% of all marine life. But now it’s getting darker.
Alarmingly, new research reveals that as the ocean darkens, the photic zone is shrinking. This will have profound ecological impacts across global oceans.
Over the last 20 years, scientists have reported that coastal surface waters are changing colour. Run-off from land, causing nutrient buildup, is fuelling large numbers of plankton blooms, such as algae. This boom in blooms reduces the amount of light penetrating surface waters below, causing coastal photic zones to darken and shrink in depth.
Now, researchers have found this process is not only limited to coastal regions, but is globally affecting “large swathes of the open ocean”, the authors write in the new study published in Global Change Biology.
