Scientists say the colors of the world’s oceans will intensify by the end of the century due to climate change, threatening the marine ecosystem from the bottom up.
The color of 50 percent of the ocean will change by the year 2100 because of changes in phytoplankton communities, according to a Massachusetts Institute of Technology study published earlier this month in Nature Communications. Scientists said the blue water in subtropic areas will appear more blue, while currently greener water near the poles will appear more green.
The phytoplankton, or algae, that scientists are talking about are small, vital marine organisms that can change in population depending on the ocean’s temperature, which several climate studies have shown is rapidly rising. The study used a climate model projecting changes to the ocean throughout the century and showed changes to the ocean’s color in a world that is 3 degrees Celsius warmer ― which scientists already predict will happen by 2100.
Water molecules absorb all parts of sunlight except for blue wavelengths, which are reflected out and give the ocean its blue hue. Phytoplankton have a green pigment called chlorophyll, so ocean surfaces with higher populations of phytoplankton appear greener and surfaces with fewer phytoplankton are more blue.
The study said climate change will cause phytoplankton to bloom in some ocean regions while reducing it in others, leading to changes in water color. Warming in subtropic areas could deprive phytoplankton of nutrients and decrease their population, but warming in polar areas could provide a better environment for them to grow. Scientists said the color changes will be too gradual for an average individual to notice over time, but the shift is a much bigger teller of other problems in the ocean.
“It could be potentially quite serious,” lead author Stephanie Dutkiewicz said in a press release. “If climate change shifts one community of phytoplankton to another, that will also change the types of food webs they can support.”
Phytoplankton make up the base of the marine life food chain, so a decrease in the algae could set off a reaction that affects the ocean’s fish populations. The algae also absorb atmospheric carbon dioxide for photosynthesis, so a reduction in phytoplankton could mean more carbon dioxide in the air.
The study said it can take a while before scientists can properly predict how climate change affects phytoplankton communities, so the next best method is to pay attention to the ocean’s color changes.
“Changes are happening because of climate change,” Dutkiewicz told The Washington Post. “It’ll be a while before we can statistically show that. But the change in the color of the ocean will be one of the early warning signals that we really have changed our planet.”