The colour of the world's oceans could soon begin to shift as warming waters trigger massive fluctuations in plankton populations, according to new research.
A study, conducted by Massachusetts Institute of Technology, suggests changes in water-dwelling phytoplankton will make some parts of the ocean bluer, and other parts greener, in one of the more unusual effects of climate change.
As these tiny organisms - which like plants on land, convert sunlight into energy - are green, their presence in the water has a big effect on its colour.
Rising global temperatures are expected to make plankton-rich polar regions even greener as huge blooms flourish, while the blue oceans of the subtropics turn bluer as plankton is wiped out.
The scientists used a computer model to gauge the effect of global warming on the world's plankton, which revealed that under current trends these changes will likely kick in within decades.
By the end of the century, more than half of the world's oceans will have shifted significantly in colour.
"The model suggests the changes won't appear huge to the naked eye, and the ocean will still look like it has blue regions in the subtropics and greener regions near the equator and poles," said Dr Stephanie Dutkiewicz, a marine ecologist at MIT.
"That basic pattern will still be there. But it'll be enough different that it will affect the rest of the food web that phytoplankton supports."
Temperature, ocean current and water acidity can all impact plankton populations, and besides climate change big natural fluctuations can take place as a result of events like El Nino.
In the new study, published in the journal Nature Communications, the scientists used satellite measurements of reflected light from the oceans recorded by satellites to make their predictions.
Dr Dutkiewicz said the results could be "potentially quite serious" as not only the number but also the varieties of plankton present in the seas shift, triggering changes that affect all ocean creatures.