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Global warming will change the colour of oceans, scientists warn – CTV News

Your favourite seaside vacation spots may look a little different by the end of the century as climate change causes the blues and greens of the oceans to become more vibrant, a new study suggests.

Scientists examining the effects of climate change on ocean ecosystems say they have developed a global model that simulates the growth of phytoplankton—microorganisms that convert sunlight into chemical energy through photosynthesis, affecting the colour of the ocean surface.

Phytoplankton contain chlorophyll, a pigment which absorbs the blue portions of sunlight to produce carbon for photosynthesis. As a result, more green light is reflected back out into the ocean, giving algae-rich regions a greenish hue.

In other words, oceans that are rich in phytoplankton tend to look greener, whereas tropical waters with less phytoplankton take on an Instagram-worthy blue or turquoise hue.

The study suggests that, as temperatures rise, blue regions will become bluer, reflecting less phytoplankton. Greener regions, including waters near the poles, may turn deeper green, as warmer temperatures encourage more diverse phytoplankton to grow.

While this shift in colour may sound picturesque, it points to the significant impact climate change has had on our oceans.

“Phytoplankton are the base of the food web—less phytoplankton [means] less food for the rest of the marine ecosystem,” study co-author Stephanie Dutkiewicz, a principal research scientist in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, told CTVNews.ca in an email.

Dutkiewicz said oceans around the world are likely already changing in colour, but the changes are likely too small for us to detect with the naked eye. The study estimates that over 50 per cent of the world’s oceans will shift in colour by the year 2100.

Since the late 1990s, satellites have been taking continuous measurements of the ocean’s colour to determine the amount of chlorophyll—and, in turn, phytoplankton—in an oceanic region. While chlorophyll levels could be altered by the effects of global warming, natural events such as El Niño can also cause an uptick in chlorophyll.

This study aimed to show how researchers can see a clear signal of climate change’s effect on phytoplankton by looking at measurements of reflected light alone—something the research community has been advocating for.

“What this study is trying to explain is that in parallel to measuring the amount of phytoplankton in the water, we should also be measuring the light coming from the water,” Maycira Costa, professor and coastal oceanography researcher at the University of Victoria, told CTV News.

“It’s an important variable that we should be tracking to understand changes in the ocean as a result of climate change.”

Over the last two years, Costa has been leading a similar research initiative in Victoria, where she installed a series of sensors on B.C. Ferries’ Queen of Oak Bay, which runs between Horseshoe Bay and Departure Bay. The sensors, which measure the colour of the water, work to calibrate satellite data in real time, providing information about the health of the Salish Sea.

The research was the first of its kind in Western Canada.

Costa hopes this latest report will reinforce the importance of understanding the effects of climate change on the world’s oceans, noting phytoplankton are “very important in the carbon cycle.”