Our oceans are changing colour, reflecting the impact climate change is having on marine ecosystems 

Darker purple means a more significant color shift. (Cael et al., Nature, 2023)

A new Nature paper uses NASA images to detect changes to our ecosystems

New findings from BIOcean5D team member Dr BB Cael, based at the UK’s National Oceanography Centre, suggests the sea is becoming steadily greener over time – and that climate breakdown is probably to blame. 

Tracking the ocean’s colour is a powerful way to monitor how ecosystems change, because colour correlates with the abundance of phytoplankton: typically, greener oceans mean greater amounts of phytoplankton. Although these chlorophyll-containing microbes are at the base of most ocean food chains, a surge in their concentrations likely has knock-on effects on ocean ecosystems, such as the creation of hypoxic dead zones and long-term effects we’re yet to understand. 

The changes were detected in more than 56% of the world’s oceans – an area greater than all land on Earth – and almost all of the tropics or subtropics. “These changes may be subtle,” said Cael in a Guardian article, “but they give an additional piece of evidence that human activity is likely affecting large parts of the global biosphere in a way that we haven’t been able to understand.”

The research, published in Nature, analysed 20 years’ of NASA satellite imagery. The findings are an output of the Horizon 2020 COMFORT project, and BB Cael was partially funded through BIOcean5D during the project. 

Find out more: read further coverage in the Guardian (UK) and Huffington Post (French).