A new study suggests that within the next few decades, areas of the ocean that look blue might appear to become “bluer.” The change won’t impact the actual water, but instead will be due to populations of marine phytoplankton that will fall as the seawater gets warmer. That phytoplankton contains the green pigment chlorophyll, which gives some ocean water a green tinge. When the number of those organisms drops, the color of the water will also appear to change.

Experts think that by 2100 more than 50% of the oceans’ 140 million square miles of the surface area could be affected. The results of their study were published this week in Nature Communications.

The changes will likely not be able to be seen by the naked eye, but instead will show up in satellite images taken above the earth’s surface. The North Atlantic Ocean and the Southern Ocean are especially vulnerable to the issue.

The problem is also more than aesthetic. Many species of fish, squid, and shellfish use the phytoplankton as a food source. Without the phytoplankton to eat they might reduce in numbers or even die out entirely. Phytoplankton also absorbs carbon dioxide. If their number reduce, then so with the amount of carbon dioxide they’re able to absorb, ultimately leading to the level of greenhouse gases to rise.